The Variations of Plasma Corticosterone/Cortisol Ratios Following ACTH Stimulation or Dexamethasone Administration in Normal Men SEIKOH NISHIDA, SHIGEICHI MATSUMURA, MASAHARU HORINO, HIDEKI OYAMA, AND ATSUKO TENKU Division of Endocrinology, Department of Medicine, Kawasaki Medical School, Kurashiki, Okayama, 701-01, Japan ABSTRACT. A radioimmunoassay for human plasma corticosterone has been developed. Plasma corticosterone increased 4.83 times as much as basal value at 60 min after an im injection of 0.25 mg synthetic /31"24 ACTH (Cortrosyn®) in normal subjects, whereas plasma cortisol increased 2.12 times as much at 60 min. And basal corticosterone/cortisol ratio of 0.053 ± 0.017 increased to 0.116 ± 0.022 (P < 0.001) after ACTH. This might be mainly due to a larger increment of corticosterone than that of cortisol after ACTH.
Corticosterone decreased to 36.7% of basal value at 4 h after 1 mg dexamethasone administration in normal subjects, whereas cortisol decreased to 13.9% of basal value at 4 h. The basal corticosterone/ cortisol ratio of 0.059 ± 0.020 increased to 0.137 ± 0.055 (0.001 < P < 0.01) after dexamethasone administration. This may have been mainly due to a more effective suppression of cortisol than that of corticosterone after dexamethasone. (/ Clin Endocrinol Metab 45: 585, 1977)
with dexamethasone. Plasma in quantities of 0.05 to 0.1 ml was extracted with 1 ml of ether and the extract was transfered to Sephadex LH-20 microcolumn with 0.2 ml of developing solvent (benzene: methanol 98:2, v/v). The height of Sephadex LH-20 microcolumn, 2 ml syringe for Mantoux reaction with diameter of 8 mm, was 60 mm. Corticosterone, cortisone and 11-deoxycortisol were separated satisfactorily on the microcolumn with benzene:methanol 98:2. The fractions containing the steroids are 1) from 3.5 to 7.0 ml for corticosterone, 2) from 1.0 to 3.0 ml for cortisone, and 3) from 7.0 to 9.0 ml for 11-deoxycortisol. The fraction containing corticosterone was incubated with 10,000 dpm of 3H-corticosterone and 0.25 ml of the antiserum solution, diluted to 1:35,000, for 30 min in room temperature. Separation of free from bound was Materials and Methods made with 0.2 ml of saturated ammonium sulfate. The mean coefficient of variation between assays was 7.7% Plasma corticosterone was determined by radioimmunoassay using an antiserum raised against corti- and within assays was 8.6%. Plasma cortisol was determined by non-chromatocosterone-21-hemisuccinate BSA (1). Conjugation of graphic radioimmunoassay using an antiserum raised corticosterone-21-hemisuccinate to BSA (bovine serum albumin) was performed according to the method of against cortisol-21-hemisuccinate BSA (3). The antiErlanger et al. (2). Rabbits were immunized every serum for cortisol prepared by immunization of rabbits four weeks by multiple sc injections of 1 mg corti- with cortisol-21-BSA cross-reacted with 11-deoxycosterone-21-BSA dissolved in saline, suspended in cortisol (23.6%), 17-OH-progesterone (22.4%), cortisone (18.2%) and corticosterone (14.2%), respectively. HowFreund's complete adjuvant. The antiserum crossever, these steroids are not present in sufficient reacted with progesterone (27.4%), DOC (20.8%) and concentrations in plasma to interfere with the deterdehydrocorticosterone (20.4%), respectively. The crossmination of cortisol. The mean plasma cortisol reactivities of two steroids, 11-deoxycortisol and cortimeasured by with-chromatographic method was not sone, which have the close polarities with corticodifferent statistically from the mean measured by sterone on the chromatography, were 6.5% and 5.1%, without-chromatographic method on 0900 h plasma respectively. The antiserum showed no cross-reactivity samples and samples from adrenal stimulation and suppression test in normal subjects. Thus, chromatographic purification of cortisol can be eliminated Received October 7, 1976. except for special plasma samples from the patients Supported in part by the Research Project Grant with excessive adrenal steroid secretion, such as of Kawasaki Medical School (50-505).
ORTICOSTERONE is the principal glucocorticoid secreted by the adrenal cortex in rats, rabbits and mice. However, little is known about the physiology of corticosterone in man and this is partly due to the lack of specific and sensitive methods for measurement of corticosterone. In the present study, plasma corticosterone was determined by radioimmunoassay and the variation of the ratio of corticosterone to cortisol, the major secretory product of the human adrenal gland, was studied before and after ACTH stimulation or dexamethasone adm i n i s trati on.
585
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586
'.ICE & M • 1977
COMMENTS TABLE 1.
Rapid ACTH test in 10 normal subjects 30 min after ACTH
Basal Case 1 2
3 4
5 6 7
8 9 10
Vol 45 • No 3
60 min after ACTH
B/F level
B/F ratio
B/F level
B/F ratio
B/F level
B/F ratio
4.8/170* 5.9/171 10.0/195 4.2/115 9.9/122 7.5/106 3.8/138 7.2/124 12.7/184 13.8/196
0.028 0.035 0.051 0.036 0.081 0.071 0.028 0.058 0.069 0.070
26.3/258* 41.9/363 43.2/328 22.1/282 27.6/218 29.9/310 25.2/210 36.7/226 24.9/275 40.2/298
0.102 0.115 0.132 0.078 0.127 0.096 0.120 0.162 0.091 0.135
28.5/296* 42.4/438 44.1/384 25.0/337 29.1/267 34.4/330 21.7/208 49.0/256 31.2/295 32.9/304
0.096 0.097 0.115 0.074 0.109 0.104 0.104 0.191 0.106 0.108
7.98 ± 3.33/** 152.1 ± 32.95
0.053** ± 0.017
31.80 ± 7.51/** 276.8 ± 47.42
0.116** ± 0.022
33.83 ± 8.32/** 311.5 ± 62.12
0.110** ± 0.028
* Corticosterone (B)/cortisol (F), ng/ml. ** Mean ± SD. adrenogenital syndrome, adrenal carcinoma or normal subjects treated with metyrapone. The antiserum cross-reacted 1.5% with dexamethasone. An aliquot (0.2 ml) of the diluted plasma (0.002 ml of plasma) and 1,000 dpm of 3H-cortisol as internal recovery were extracted with 1 ml ether. The extract was incubated with 10,000 dpm of 3H-cortisol and 0.25 ml of the antiserum, diluted to 1:55,000, for 30 min in room temperature. Separation of free from bound was made with 0.2 ml of saturated ammonium sulfate. The mean coefficient of variation for between assay and within assay were 7.0% and 8.4%. A rapid ACTH test was performed in 10 normal adult volunteers. Blood samples were obtained before (0900 h), and at 30 min and at 60 min after an im injection of 0.25 mg of synthetic /31"24 ACTH (Cortrosyn®) for determinations of corticosterone and cortisol.
Single dose 4-h dexamethasone suppression test (4) was performed in 10 normal adult volunteers. Blood samples were obtained before (0900 h), and at 2 h and at 4 h after administration of 1 mg of dexamethasone.
Results As seen in Table 1, basal levels of corticosterone and cortisol at 0900 h were 7.98 ± 3.33 ng/ml and 152.1 ± 32.95 ng/ml, respectively, for a rapid ACTH test in 10 normal subjects. At 30 min after ACTH, corticosterone and cortisol levels were 31.80 ± 7.51 ng/ml and 276.8 ± 47.42 ng/ml and at 60 min, these levels were 33.83 ± 8.32 ng/ml and 311.5 ± 62.12 ng/ml, respectively. The basal corticosterone/cortisol ratio was
TABLE 2. Single dose 4-h dexamethasone suppression test in 10 normal subjects Basal Case 1 2 3 4
5 6 7 8 9 10
2 h after dexa.
4 h after dexa.
B/F level
B/F ratio
B/F level
B/F ratio
B/F level
B/F ratio
10.1/135* 7.4/86 10.6/150 7.0/96 3.3/126 4.0/83 5.6/73 3.0/81 3.7/103 10.1/167
0.075 0.086 0.071 0.073 0.026 0.048 0.077 0.037 0.036 0.060
2.6/59* 2.4/18 2.3/80 1.4/30 1.9/38 2.5/20 3.0/21 2.1/27 2.0/51 2.5/39
0.044 0.133 0.029 0.047 0.050 0.125 0.143 0.078 0.039 0.064
0.85/14* 1.8/10 1.3/26 1.8/10 1.4/15 2.0/16 2.4/11 1.6/13 2.8/14 3.2/23
0.061 0.180 0.050 0.180 0.093 0.125 0.218 0.123 0.200 0.139
6.48 ± 2.85/** 110.0 ± 30.81
0.059** ± 0.020
2.27 ± 0.42/** 38.3 ± 18.90
0.075** ± 0.040
1.92 ± 0.68/** 15.2 ± 5.08
0.137** ± 0.055
* Corticosterone (B)/cortisol (F), ng/ml. ** Mean ± SD.
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587
COMMENTS 0.053 ± 0.017 and it increased significantly to 0.116 ±0.022 ( P < 0.001) at 30 min, and to 0.110 ± 0.028 (P < 0.001) at 60 min after ACTH. Table 3 shows the responses of corticosterone and cortisol to ACTH stimulation. Plasma corticosterone increased 4.55 times as much as basal value at 30 min and 4.83 times as much at 60 min after ACTH, whereas plasma cortisol increased 1.88 times at 30 min and 2.12 times at 60 min after ACTH. These differences in the response to ACTH between corticosterone and cortisol at 30 min ( P < 0.001) and at 60 min (0.001 < P < 0.01) were significant. As seen in Table 2, basal levels of corticosterone and cortisol were 6.48 ± 2.85 ng/ml and 110.0 ± 30.81 ng/ml, respectively, for a single dose 4-h dexamethasone suppression test in 10 normal subjects. At 2 h after dexamethasone, corticosterone and cortisol levels were 2.27 ± 0.42 ng/ml and 38.30 ± 18.90 ng/ml, and at 4 h, these levels were 1.92 ± 0.68 ng/ml and 15.20 ± 5.08 ng/ml, respectively. Basal corticosterone/ cortisol ratio was 0.059 ± 0.020 and it increased, with no significance, to 0.075 ± 0.040 at 2 h, and significantly to 0.137 ± 0.055 ( 0 . 0 0 K P < 0.01) at 4 h after dexamethasone. Table 3 shows the suppressibility of corticosterone and cortisol to dexamethasone administration. Plasma corticosterone decreased to 42.2% of basal level at 2 h after dexamethasone and to 36.7% at 4 h, whereas plasma cortisol decreased to 33.8% at 2 h and to 13.9% at 4 h after dexamethasone. The difference in suppresibility between corticosterone and cortisol at 4 h was significant (0.001 < P < 0.01).
for corticosterone in human blood are those of Underwood et al. (5), West et al. (6) and Vecsei (7). The present study presents one of the few investigations about radioimmunoassay of corticosterone in human plasma. The basal corticosterone/cortisol ratio at 0900 h is, in average, 0.056 in the present study (Tables 1, 2), which agrees with those values previously obtained by double isotope derivative methods (8,9). In the ACTH test, basal corticosterone/cortisol ratio increased twice as much at 30 min and 60 min after ACTH, and this might be due to a larger increment of corticosterone than that of cortisol (Table 3). That corticosterone secretion is stimulated to a higher degree by ACTH than that of cortisol has been suggested by earlier studies using isotope derivative procedure (8, 10), fluorometry (11) or competitive protein binding assay (12). Also, in the single dose 4-h 1 mg dexamethasone suppression test which we have developed (4), basal corticosterone/cortisol ratio increased twice as much at 4 h after dexamethasone and this may have been mainly due to a more effective suppression of cortisol than that of corticosterone. An earlier study by competitive protein binding assay (12) suggests that cortisol secretion is suppressed more effectively by dexamethasone than that of corticosterone. In conclusion, it appears from the present study that the secretion of corticosterone is more susceptible to exogenous ACTH stimulation than that of cortisol, and that corticosterone has a poorer dexamethasone suppressibility than cortisol.
Discussion
Acknowledgments
A radioimmunoassay for corticosterone is lacking except for a few works, most of which are concerned with blood corticosterone of rat. So far the only papers about radioimmunoassay
The authors are indebted to Miss Kazuko Okazaki for expert technical assistance in the determination of cortisol. Cortrosyn was generously supplied by Daiichi Seiyaku Co., Ltd., Japan.
TABLE 3. Responses of corticosterone and cortisol to ACTH stimulation or single dose dexamethasone suppression in 10 normal subjects Rapid ACTH test
Corticosterone Cortisol
4-h suppression test
30 min/basal*
60 min/basal*
2 h/basal*
4 h/basal*
4.55 ± 1.59 1.88 ± 0.45
4.83 ± 1.68 2.12 ± 0.54
0.422 ±0.181 0.338 ± 0.106
0.367 ±0.193 0.139 ± 0.028
* Ratios of corticosterone or cortisol levels at 30 min, 60 min, 2 h and 4 h to basal corticosterone or cortisol levels and expressed by mean ± SD.
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COMMENTS
588
References 1. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, A radioimmunoassay for human plasma corticosterone, Endocrinol Jap 23: 465, 1976. 2. Erlanger, B. F., F. Borek, S. M. Beiser, and S. Lieberman, Steroid-protein conjugates. I. Preparation and characterization of conjugates of bovine serum albumin with testosterone and with cortisone, J Biol Chem 228: 713, 1957. 3. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, Radioimmunoassay for steroid hormones. I. A radioimmunoassay for plasma cortisol, Kawasaki MedJ 2: 81, 1976. 4. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, Single dose four hour dexamethasone suppression test in normal men and its application for the diagnosis of Cushing's syndrome, Steroids 28: 411, 1976. 5. Underwood, R. H., and G. H. Williams, The simultaneous measurement of aldosterone, cortisol and corticosterone in human peripheral plasma by displacement analysis, / Lab Clin Med 79: 848, 1972. 6. West, C. D., D. K. Mahajan, V. J. Chavre, C. J.
7. 8.
9.
10. 11.
12.
JCE&M . 1977 Vol45 i No 3
Nabors, and F. H. Tyler, Simultaneous measurement of multiple steroids by radioimmunoassay demonstrating episodic secretion, J Clin Endocrinol Metab 36: 1230, 1973. Vecsei, P., In Jaffe, B. M., and H. R. Behrman (eds.), Methods of Hormone Radioimmunoassay, Academic Press, New York, 1974, p. 393. Fraser, R., and V. H. T. James, Double isotope assay of aldosterone, corticosterone and cortisol in human peripheral plasma,/ Endocrinol 40: 59, 1968. Brorson, I., Concentration of corticosterone and cortisol in peripheral plasma of patients with adrenocortical hyperplasia and normal subjects, Ada Endocrinol (Kbh) 58: 445, 1968. Peterson, R. E., Plasma corticosterone and hydrocortisone levels in man, 7 Clin Endocrinol Metab 17: 1150, 1957. Martin, M. M., and A. L. A. Martin, Simultaneous fluorometric determination of cortisol and corticosterone in human plasma,/ Clin Endocrinol Metab 28: 137, 1968. Newsome, H. H., Jr., A. S. Clements, and E. H. Borum, The simultaneous assay of cortisol, corticosterone, 11-deoxycortisol, and cortisone in human plasma, J Clin Endocrinol Metab 34: 473, 1972.
Effect of 1-5 Hydroxytryptophan Infusion on Growth Hormone and Prolactin Secretion in Man IOANA LANCRANJAN,* ANNA WIRZ-JUSTICE,f W. PUHRINGER,f AND E. DEL POZO* *Department of Experimental Therapeutics, Medical and Biological Research Division, Sandoz Ltd., Basle, Switzerland, and ^Psychiatric University Clinic, Basle, Switzerland ABSTRACT. The effect of a new soluble ester of 1-5 hydroxytryptophan (1-5 HTP, Ro 3-5940, 200 mg infusion) on prolactin (PRL) and growth hormone (GH) release was tested in 11 young, healthy subjects (6 men, 5 women). To minimize side-effects, peripheral decarboxylase inhibition was achieved with benserazide (Ro 4-4602.) PRL increased significantly (P
Corticosterone decreased to 36.7% of basal value at 4 h after 1 mg dexamethasone administration in normal subjects, whereas cortisol decreased to 13.9% of basal value at 4 h. The basal corticosterone/ cortisol ratio of 0.059 ± 0.020 increased to 0.137 ± 0.055 (0.001 < P < 0.01) after dexamethasone administration. This may have been mainly due to a more effective suppression of cortisol than that of corticosterone after dexamethasone. (/ Clin Endocrinol Metab 45: 585, 1977)
with dexamethasone. Plasma in quantities of 0.05 to 0.1 ml was extracted with 1 ml of ether and the extract was transfered to Sephadex LH-20 microcolumn with 0.2 ml of developing solvent (benzene: methanol 98:2, v/v). The height of Sephadex LH-20 microcolumn, 2 ml syringe for Mantoux reaction with diameter of 8 mm, was 60 mm. Corticosterone, cortisone and 11-deoxycortisol were separated satisfactorily on the microcolumn with benzene:methanol 98:2. The fractions containing the steroids are 1) from 3.5 to 7.0 ml for corticosterone, 2) from 1.0 to 3.0 ml for cortisone, and 3) from 7.0 to 9.0 ml for 11-deoxycortisol. The fraction containing corticosterone was incubated with 10,000 dpm of 3H-corticosterone and 0.25 ml of the antiserum solution, diluted to 1:35,000, for 30 min in room temperature. Separation of free from bound was Materials and Methods made with 0.2 ml of saturated ammonium sulfate. The mean coefficient of variation between assays was 7.7% Plasma corticosterone was determined by radioimmunoassay using an antiserum raised against corti- and within assays was 8.6%. Plasma cortisol was determined by non-chromatocosterone-21-hemisuccinate BSA (1). Conjugation of graphic radioimmunoassay using an antiserum raised corticosterone-21-hemisuccinate to BSA (bovine serum albumin) was performed according to the method of against cortisol-21-hemisuccinate BSA (3). The antiErlanger et al. (2). Rabbits were immunized every serum for cortisol prepared by immunization of rabbits four weeks by multiple sc injections of 1 mg corti- with cortisol-21-BSA cross-reacted with 11-deoxycosterone-21-BSA dissolved in saline, suspended in cortisol (23.6%), 17-OH-progesterone (22.4%), cortisone (18.2%) and corticosterone (14.2%), respectively. HowFreund's complete adjuvant. The antiserum crossever, these steroids are not present in sufficient reacted with progesterone (27.4%), DOC (20.8%) and concentrations in plasma to interfere with the deterdehydrocorticosterone (20.4%), respectively. The crossmination of cortisol. The mean plasma cortisol reactivities of two steroids, 11-deoxycortisol and cortimeasured by with-chromatographic method was not sone, which have the close polarities with corticodifferent statistically from the mean measured by sterone on the chromatography, were 6.5% and 5.1%, without-chromatographic method on 0900 h plasma respectively. The antiserum showed no cross-reactivity samples and samples from adrenal stimulation and suppression test in normal subjects. Thus, chromatographic purification of cortisol can be eliminated Received October 7, 1976. except for special plasma samples from the patients Supported in part by the Research Project Grant with excessive adrenal steroid secretion, such as of Kawasaki Medical School (50-505).
ORTICOSTERONE is the principal glucocorticoid secreted by the adrenal cortex in rats, rabbits and mice. However, little is known about the physiology of corticosterone in man and this is partly due to the lack of specific and sensitive methods for measurement of corticosterone. In the present study, plasma corticosterone was determined by radioimmunoassay and the variation of the ratio of corticosterone to cortisol, the major secretory product of the human adrenal gland, was studied before and after ACTH stimulation or dexamethasone adm i n i s trati on.
585
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586
'.ICE & M • 1977
COMMENTS TABLE 1.
Rapid ACTH test in 10 normal subjects 30 min after ACTH
Basal Case 1 2
3 4
5 6 7
8 9 10
Vol 45 • No 3
60 min after ACTH
B/F level
B/F ratio
B/F level
B/F ratio
B/F level
B/F ratio
4.8/170* 5.9/171 10.0/195 4.2/115 9.9/122 7.5/106 3.8/138 7.2/124 12.7/184 13.8/196
0.028 0.035 0.051 0.036 0.081 0.071 0.028 0.058 0.069 0.070
26.3/258* 41.9/363 43.2/328 22.1/282 27.6/218 29.9/310 25.2/210 36.7/226 24.9/275 40.2/298
0.102 0.115 0.132 0.078 0.127 0.096 0.120 0.162 0.091 0.135
28.5/296* 42.4/438 44.1/384 25.0/337 29.1/267 34.4/330 21.7/208 49.0/256 31.2/295 32.9/304
0.096 0.097 0.115 0.074 0.109 0.104 0.104 0.191 0.106 0.108
7.98 ± 3.33/** 152.1 ± 32.95
0.053** ± 0.017
31.80 ± 7.51/** 276.8 ± 47.42
0.116** ± 0.022
33.83 ± 8.32/** 311.5 ± 62.12
0.110** ± 0.028
* Corticosterone (B)/cortisol (F), ng/ml. ** Mean ± SD. adrenogenital syndrome, adrenal carcinoma or normal subjects treated with metyrapone. The antiserum cross-reacted 1.5% with dexamethasone. An aliquot (0.2 ml) of the diluted plasma (0.002 ml of plasma) and 1,000 dpm of 3H-cortisol as internal recovery were extracted with 1 ml ether. The extract was incubated with 10,000 dpm of 3H-cortisol and 0.25 ml of the antiserum, diluted to 1:55,000, for 30 min in room temperature. Separation of free from bound was made with 0.2 ml of saturated ammonium sulfate. The mean coefficient of variation for between assay and within assay were 7.0% and 8.4%. A rapid ACTH test was performed in 10 normal adult volunteers. Blood samples were obtained before (0900 h), and at 30 min and at 60 min after an im injection of 0.25 mg of synthetic /31"24 ACTH (Cortrosyn®) for determinations of corticosterone and cortisol.
Single dose 4-h dexamethasone suppression test (4) was performed in 10 normal adult volunteers. Blood samples were obtained before (0900 h), and at 2 h and at 4 h after administration of 1 mg of dexamethasone.
Results As seen in Table 1, basal levels of corticosterone and cortisol at 0900 h were 7.98 ± 3.33 ng/ml and 152.1 ± 32.95 ng/ml, respectively, for a rapid ACTH test in 10 normal subjects. At 30 min after ACTH, corticosterone and cortisol levels were 31.80 ± 7.51 ng/ml and 276.8 ± 47.42 ng/ml and at 60 min, these levels were 33.83 ± 8.32 ng/ml and 311.5 ± 62.12 ng/ml, respectively. The basal corticosterone/cortisol ratio was
TABLE 2. Single dose 4-h dexamethasone suppression test in 10 normal subjects Basal Case 1 2 3 4
5 6 7 8 9 10
2 h after dexa.
4 h after dexa.
B/F level
B/F ratio
B/F level
B/F ratio
B/F level
B/F ratio
10.1/135* 7.4/86 10.6/150 7.0/96 3.3/126 4.0/83 5.6/73 3.0/81 3.7/103 10.1/167
0.075 0.086 0.071 0.073 0.026 0.048 0.077 0.037 0.036 0.060
2.6/59* 2.4/18 2.3/80 1.4/30 1.9/38 2.5/20 3.0/21 2.1/27 2.0/51 2.5/39
0.044 0.133 0.029 0.047 0.050 0.125 0.143 0.078 0.039 0.064
0.85/14* 1.8/10 1.3/26 1.8/10 1.4/15 2.0/16 2.4/11 1.6/13 2.8/14 3.2/23
0.061 0.180 0.050 0.180 0.093 0.125 0.218 0.123 0.200 0.139
6.48 ± 2.85/** 110.0 ± 30.81
0.059** ± 0.020
2.27 ± 0.42/** 38.3 ± 18.90
0.075** ± 0.040
1.92 ± 0.68/** 15.2 ± 5.08
0.137** ± 0.055
* Corticosterone (B)/cortisol (F), ng/ml. ** Mean ± SD.
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587
COMMENTS 0.053 ± 0.017 and it increased significantly to 0.116 ±0.022 ( P < 0.001) at 30 min, and to 0.110 ± 0.028 (P < 0.001) at 60 min after ACTH. Table 3 shows the responses of corticosterone and cortisol to ACTH stimulation. Plasma corticosterone increased 4.55 times as much as basal value at 30 min and 4.83 times as much at 60 min after ACTH, whereas plasma cortisol increased 1.88 times at 30 min and 2.12 times at 60 min after ACTH. These differences in the response to ACTH between corticosterone and cortisol at 30 min ( P < 0.001) and at 60 min (0.001 < P < 0.01) were significant. As seen in Table 2, basal levels of corticosterone and cortisol were 6.48 ± 2.85 ng/ml and 110.0 ± 30.81 ng/ml, respectively, for a single dose 4-h dexamethasone suppression test in 10 normal subjects. At 2 h after dexamethasone, corticosterone and cortisol levels were 2.27 ± 0.42 ng/ml and 38.30 ± 18.90 ng/ml, and at 4 h, these levels were 1.92 ± 0.68 ng/ml and 15.20 ± 5.08 ng/ml, respectively. Basal corticosterone/ cortisol ratio was 0.059 ± 0.020 and it increased, with no significance, to 0.075 ± 0.040 at 2 h, and significantly to 0.137 ± 0.055 ( 0 . 0 0 K P < 0.01) at 4 h after dexamethasone. Table 3 shows the suppressibility of corticosterone and cortisol to dexamethasone administration. Plasma corticosterone decreased to 42.2% of basal level at 2 h after dexamethasone and to 36.7% at 4 h, whereas plasma cortisol decreased to 33.8% at 2 h and to 13.9% at 4 h after dexamethasone. The difference in suppresibility between corticosterone and cortisol at 4 h was significant (0.001 < P < 0.01).
for corticosterone in human blood are those of Underwood et al. (5), West et al. (6) and Vecsei (7). The present study presents one of the few investigations about radioimmunoassay of corticosterone in human plasma. The basal corticosterone/cortisol ratio at 0900 h is, in average, 0.056 in the present study (Tables 1, 2), which agrees with those values previously obtained by double isotope derivative methods (8,9). In the ACTH test, basal corticosterone/cortisol ratio increased twice as much at 30 min and 60 min after ACTH, and this might be due to a larger increment of corticosterone than that of cortisol (Table 3). That corticosterone secretion is stimulated to a higher degree by ACTH than that of cortisol has been suggested by earlier studies using isotope derivative procedure (8, 10), fluorometry (11) or competitive protein binding assay (12). Also, in the single dose 4-h 1 mg dexamethasone suppression test which we have developed (4), basal corticosterone/cortisol ratio increased twice as much at 4 h after dexamethasone and this may have been mainly due to a more effective suppression of cortisol than that of corticosterone. An earlier study by competitive protein binding assay (12) suggests that cortisol secretion is suppressed more effectively by dexamethasone than that of corticosterone. In conclusion, it appears from the present study that the secretion of corticosterone is more susceptible to exogenous ACTH stimulation than that of cortisol, and that corticosterone has a poorer dexamethasone suppressibility than cortisol.
Discussion
Acknowledgments
A radioimmunoassay for corticosterone is lacking except for a few works, most of which are concerned with blood corticosterone of rat. So far the only papers about radioimmunoassay
The authors are indebted to Miss Kazuko Okazaki for expert technical assistance in the determination of cortisol. Cortrosyn was generously supplied by Daiichi Seiyaku Co., Ltd., Japan.
TABLE 3. Responses of corticosterone and cortisol to ACTH stimulation or single dose dexamethasone suppression in 10 normal subjects Rapid ACTH test
Corticosterone Cortisol
4-h suppression test
30 min/basal*
60 min/basal*
2 h/basal*
4 h/basal*
4.55 ± 1.59 1.88 ± 0.45
4.83 ± 1.68 2.12 ± 0.54
0.422 ±0.181 0.338 ± 0.106
0.367 ±0.193 0.139 ± 0.028
* Ratios of corticosterone or cortisol levels at 30 min, 60 min, 2 h and 4 h to basal corticosterone or cortisol levels and expressed by mean ± SD.
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COMMENTS
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References 1. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, A radioimmunoassay for human plasma corticosterone, Endocrinol Jap 23: 465, 1976. 2. Erlanger, B. F., F. Borek, S. M. Beiser, and S. Lieberman, Steroid-protein conjugates. I. Preparation and characterization of conjugates of bovine serum albumin with testosterone and with cortisone, J Biol Chem 228: 713, 1957. 3. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, Radioimmunoassay for steroid hormones. I. A radioimmunoassay for plasma cortisol, Kawasaki MedJ 2: 81, 1976. 4. Nishida, S., S. Matsumura, M. Horino, H. Oyama, and A. Tenku, Single dose four hour dexamethasone suppression test in normal men and its application for the diagnosis of Cushing's syndrome, Steroids 28: 411, 1976. 5. Underwood, R. H., and G. H. Williams, The simultaneous measurement of aldosterone, cortisol and corticosterone in human peripheral plasma by displacement analysis, / Lab Clin Med 79: 848, 1972. 6. West, C. D., D. K. Mahajan, V. J. Chavre, C. J.
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Nabors, and F. H. Tyler, Simultaneous measurement of multiple steroids by radioimmunoassay demonstrating episodic secretion, J Clin Endocrinol Metab 36: 1230, 1973. Vecsei, P., In Jaffe, B. M., and H. R. Behrman (eds.), Methods of Hormone Radioimmunoassay, Academic Press, New York, 1974, p. 393. Fraser, R., and V. H. T. James, Double isotope assay of aldosterone, corticosterone and cortisol in human peripheral plasma,/ Endocrinol 40: 59, 1968. Brorson, I., Concentration of corticosterone and cortisol in peripheral plasma of patients with adrenocortical hyperplasia and normal subjects, Ada Endocrinol (Kbh) 58: 445, 1968. Peterson, R. E., Plasma corticosterone and hydrocortisone levels in man, 7 Clin Endocrinol Metab 17: 1150, 1957. Martin, M. M., and A. L. A. Martin, Simultaneous fluorometric determination of cortisol and corticosterone in human plasma,/ Clin Endocrinol Metab 28: 137, 1968. Newsome, H. H., Jr., A. S. Clements, and E. H. Borum, The simultaneous assay of cortisol, corticosterone, 11-deoxycortisol, and cortisone in human plasma, J Clin Endocrinol Metab 34: 473, 1972.
Effect of 1-5 Hydroxytryptophan Infusion on Growth Hormone and Prolactin Secretion in Man IOANA LANCRANJAN,* ANNA WIRZ-JUSTICE,f W. PUHRINGER,f AND E. DEL POZO* *Department of Experimental Therapeutics, Medical and Biological Research Division, Sandoz Ltd., Basle, Switzerland, and ^Psychiatric University Clinic, Basle, Switzerland ABSTRACT. The effect of a new soluble ester of 1-5 hydroxytryptophan (1-5 HTP, Ro 3-5940, 200 mg infusion) on prolactin (PRL) and growth hormone (GH) release was tested in 11 young, healthy subjects (6 men, 5 women). To minimize side-effects, peripheral decarboxylase inhibition was achieved with benserazide (Ro 4-4602.) PRL increased significantly (P
