Pharmacology & Toxicology 1991, 69, 6 M 3 .
Nifedipine Increases Urinary Excretion of Prostacyclin Metabolite in Hypertensive Pregnancy 'Auli Manninen, 'Timo Metsii-Ketela, *Risto'himala and 'Heikki Vapaatalo
IDepartment of Biomedical Sciences, University of Tampere, Box 607, SF-33 101 Tampere, Finland and ,Department of Gynecology and Obstetrics, Tampere University Central Hospital, SF-33520 Tampere, Finland (Received November 1, 1990; Accepted February 20, 1991) Abstract: Renal prostanoid excretion was investigated in nine hypertensive pregnant patients before and during treatment with nifedipine 10 mg orally t.i.d. Urinary excretion of prostacyclin (measured as 6-ketoprostaglandin F,,, 6-keto-PGF,,) increased by 77% during nifedipine treatment (P
140/90 mmHg, on at least two occasions six hr or more apart, or an increase in blood pressure, > 30/15 mmHg, with persistent proteinuria, >0.3 g per day (=pre-eclampsia, n=4), or without proteinuria (=gestational hypertension, n = 5). All patients followed a normal hospital diet containing 2 8 5 mmol sodium per day. Nifedipine treatment (10 mg orally t.i.d.) began at gestational week 33 (mean) and the patients delivered at gestational week 36 (mean). For ethical reasons, normotensive pregnant controls could not be included. However, six healthy normotensive, non-pregnant women (age 22-25 years) on their usual diet entered the study. They received nifedipine for five days, 10 mg orally t.i.d. Blood pressure was measured by cuff manometry two to six times daily under standardized conditions, in the left recumbent position on the right arm by the same well trained midwives. The means of the blood pressure measurements during two days prior to medication and on the fourth to fifth days during medication were calculated. Blood samples were taken one to two days, and daily urine was collected during the 24 hr before nifedipine treatment. The second samples were taken on the fifth day. Fasting blood samples were drawn from the antecubital vein in the morning. Samples for plasma prekallikrein were drawn through a plastic cannula to avoid contact with metal. In the case of the non-pregnant subjects, the samples were collected similarly before, and on the fifth day of nifedipine treatment. Serum and urine creatinine was determined using a Technicon RA 1000 analyzer (Technicon Instruments, Tarrytown, NY, USA) and creatinine clearance was calculated. Daily urine sodium was analyzed by a flame photometer IL 743 (Instrumentation Laboratory, Paderno Dugnano, Italy). Plasma prekallikrein and urinary kallikrein were determined by the methods of Friberger et al. (1979) and Amundsen et al. (1979), respectively, using the chromogenic substrates S-2302 and S-2266 (Kabi Diagnostica, Stockholm, Sweden). Urinary catecholamines were purified with cation-exchange columns (Bio Rex 70, BioRad Laboratories, Richmond, CA, U.S.A.) and analyzed by HPLC with an electrochemical detector (Goldstein er al. 1981). Urine prostanoid concentrations were determined by a modification of the double antibody procedure (Seppala et al. 1984) using commercial antisera (PGE,: Pasteur Institute, Paris, France; 6-keto-PGF,,: Dr. Istvan Mucha, Institute of Isotopes of the Hungarian Academy of Sciences, Budapest, Hungary; TxB,: Prof. Christel Taube, Martin-Luther University, Halle, Germany). The statistical analysis was performed using Student's paired and
NIFEDIPINE AND URINARY PROSTANOIDS
61
Table I.
Laboratory parameters in hypertensive pregnant subjects before and on the fifth day of nifedipine treatment 10 mg t.i.d. orally. Means+ S.E.M. (and medians) are given. n = 9, * P < 0.05. Basal 1.41k0.32 1467k84 88+12 45.0 & 3.4 5.6k2.0 257 k54 19k2 1223 217 326 +69 1594 372 7.6k2.3
Creatinine clearance (I&' s-' 1.74 cm') Urinary volume (ml 24 hr-') Urinary sodium (mmol 1-') Plasma prekallikrein (nkat I-') Urinary kallikrein (nkat 1-I)
Urinary noradrenaline (nmol 24 hr-I) Urinary adrenaline (nmol 24 hr-I) Urinary PGE, (ng 24 hr-I) Urinary 6-keto-PGFI, (ng 24 hr-I) Urinary TxB, (ng 24 hr-l) Urinary TxB,/6-keto-PGFI,
unpaired t-tests and Wilcoxon rank sum tests for paired and unpaired samples. Correlations were measured by Spearman's correlation coefficient. A P-value less than 0.05 was considered statistically significant. The work was approved by the Ethical Committee of the University Central Hospital of Tampere.
Results
Nifedipine reduced blood pressure from 158/ 103 4/ 1 to 150/96+4/2 (P < 0.001) in the pregnant subjects. The effects of nifedipine on the laboratory parameters in the patients and in the non-pregnant women are presented in tables 1 and 2. Urinary excretion of 6-keto-PGF,, increased significantly during nifedipine in the hypertensive pregnant patients (P < 0.05). TXB, and PGE, excretions showed no significant changes. The TXB,/dketo-PGF,, ratio tended to decrease (P =0.07). Compared with the non-pregnant women, plasma prekallikrein levels in the patients with hypertensive pregnancy were higher both before (P = 0.06) and during (P < 0.01) nifedipine treatment. Urinary excretion of PGE, was significantly lower (P < 0.05) before but not during the medication. The excretions of 6-keto-PGF,,, TXB,, catecholamines and kallikrein did not differ significantly from those of non-pregnant subjects. In the non-pregnant women, the variations were wide in
On nifedipine (1.56)
(1451) (79)
(46.4)
1.55+0.46 1755k 123 91+8
(18)
47.1 +3.3 7.8 f 3.0 265 + 33 23+4
(380)
1392+359 577 f75
(5.9)
(220) (1074) ( 1722)
1087k 125 2.5k0.6
(1.30) (1850)* (87)
(47.4) (5.6)
(230) (23) (1 392)
(557)* (1056)
prostanoid excretions, and n o significant changes were found during nifedipine. Plasma prekallikrein decreased (P < 0.05) and urinary kallikrein (P < 0.05) and noradrenaline (P = 0.06) excretions increased during nifedipine treatment. The urinary excretions of kallikrein, catecholamines and prostanoids were also related to creatinine clearance. No essential differences were found when the results were compared with those expressed as daily excretions. In the hypertensive patients of this study the decrease in blood pressure did not correlate with basal levels or changes in prostanoid, catecholamine o r kallikrein excretions nor in plasma prekallikrein. Neither did prostanoid excretions correlate with kallikrein or catecholamine excretions or plasma prekallikrein. No correlations between daily urine sodium and prostanoid excretions were observed. However, in the non-pregnant women there was a correlation between daily urine sodium and PGE, excretions (r, = 0.829, P < 0.05) during nifedipine treatment, but not prior to it.
Discussion PGE,, 6-keto-PGF,, and TXB, in urine are generally considered as indicators of renal prostanoid formation (Seyberth et al. 1988). However, an extrarenal contribution cannot be completely excluded in the urinary excretions of 6-
Table 2. Laboratory parameters in non-pregnant normotensive women before and on the fifth day of nifedipine treatment 10 mg t.i.d. orally.
MeansfS.E.M. (and medians) are given. n=6, * P
Nifedipine Increases Urinary Excretion of Prostacyclin Metabolite in Hypertensive Pregnancy 'Auli Manninen, 'Timo Metsii-Ketela, *Risto'himala and 'Heikki Vapaatalo
IDepartment of Biomedical Sciences, University of Tampere, Box 607, SF-33 101 Tampere, Finland and ,Department of Gynecology and Obstetrics, Tampere University Central Hospital, SF-33520 Tampere, Finland (Received November 1, 1990; Accepted February 20, 1991) Abstract: Renal prostanoid excretion was investigated in nine hypertensive pregnant patients before and during treatment with nifedipine 10 mg orally t.i.d. Urinary excretion of prostacyclin (measured as 6-ketoprostaglandin F,,, 6-keto-PGF,,) increased by 77% during nifedipine treatment (P
140/90 mmHg, on at least two occasions six hr or more apart, or an increase in blood pressure, > 30/15 mmHg, with persistent proteinuria, >0.3 g per day (=pre-eclampsia, n=4), or without proteinuria (=gestational hypertension, n = 5). All patients followed a normal hospital diet containing 2 8 5 mmol sodium per day. Nifedipine treatment (10 mg orally t.i.d.) began at gestational week 33 (mean) and the patients delivered at gestational week 36 (mean). For ethical reasons, normotensive pregnant controls could not be included. However, six healthy normotensive, non-pregnant women (age 22-25 years) on their usual diet entered the study. They received nifedipine for five days, 10 mg orally t.i.d. Blood pressure was measured by cuff manometry two to six times daily under standardized conditions, in the left recumbent position on the right arm by the same well trained midwives. The means of the blood pressure measurements during two days prior to medication and on the fourth to fifth days during medication were calculated. Blood samples were taken one to two days, and daily urine was collected during the 24 hr before nifedipine treatment. The second samples were taken on the fifth day. Fasting blood samples were drawn from the antecubital vein in the morning. Samples for plasma prekallikrein were drawn through a plastic cannula to avoid contact with metal. In the case of the non-pregnant subjects, the samples were collected similarly before, and on the fifth day of nifedipine treatment. Serum and urine creatinine was determined using a Technicon RA 1000 analyzer (Technicon Instruments, Tarrytown, NY, USA) and creatinine clearance was calculated. Daily urine sodium was analyzed by a flame photometer IL 743 (Instrumentation Laboratory, Paderno Dugnano, Italy). Plasma prekallikrein and urinary kallikrein were determined by the methods of Friberger et al. (1979) and Amundsen et al. (1979), respectively, using the chromogenic substrates S-2302 and S-2266 (Kabi Diagnostica, Stockholm, Sweden). Urinary catecholamines were purified with cation-exchange columns (Bio Rex 70, BioRad Laboratories, Richmond, CA, U.S.A.) and analyzed by HPLC with an electrochemical detector (Goldstein er al. 1981). Urine prostanoid concentrations were determined by a modification of the double antibody procedure (Seppala et al. 1984) using commercial antisera (PGE,: Pasteur Institute, Paris, France; 6-keto-PGF,,: Dr. Istvan Mucha, Institute of Isotopes of the Hungarian Academy of Sciences, Budapest, Hungary; TxB,: Prof. Christel Taube, Martin-Luther University, Halle, Germany). The statistical analysis was performed using Student's paired and
NIFEDIPINE AND URINARY PROSTANOIDS
61
Table I.
Laboratory parameters in hypertensive pregnant subjects before and on the fifth day of nifedipine treatment 10 mg t.i.d. orally. Means+ S.E.M. (and medians) are given. n = 9, * P < 0.05. Basal 1.41k0.32 1467k84 88+12 45.0 & 3.4 5.6k2.0 257 k54 19k2 1223 217 326 +69 1594 372 7.6k2.3
Creatinine clearance (I&' s-' 1.74 cm') Urinary volume (ml 24 hr-') Urinary sodium (mmol 1-') Plasma prekallikrein (nkat I-') Urinary kallikrein (nkat 1-I)
Urinary noradrenaline (nmol 24 hr-I) Urinary adrenaline (nmol 24 hr-I) Urinary PGE, (ng 24 hr-I) Urinary 6-keto-PGFI, (ng 24 hr-I) Urinary TxB, (ng 24 hr-l) Urinary TxB,/6-keto-PGFI,
unpaired t-tests and Wilcoxon rank sum tests for paired and unpaired samples. Correlations were measured by Spearman's correlation coefficient. A P-value less than 0.05 was considered statistically significant. The work was approved by the Ethical Committee of the University Central Hospital of Tampere.
Results
Nifedipine reduced blood pressure from 158/ 103 4/ 1 to 150/96+4/2 (P < 0.001) in the pregnant subjects. The effects of nifedipine on the laboratory parameters in the patients and in the non-pregnant women are presented in tables 1 and 2. Urinary excretion of 6-keto-PGF,, increased significantly during nifedipine in the hypertensive pregnant patients (P < 0.05). TXB, and PGE, excretions showed no significant changes. The TXB,/dketo-PGF,, ratio tended to decrease (P =0.07). Compared with the non-pregnant women, plasma prekallikrein levels in the patients with hypertensive pregnancy were higher both before (P = 0.06) and during (P < 0.01) nifedipine treatment. Urinary excretion of PGE, was significantly lower (P < 0.05) before but not during the medication. The excretions of 6-keto-PGF,,, TXB,, catecholamines and kallikrein did not differ significantly from those of non-pregnant subjects. In the non-pregnant women, the variations were wide in
On nifedipine (1.56)
(1451) (79)
(46.4)
1.55+0.46 1755k 123 91+8
(18)
47.1 +3.3 7.8 f 3.0 265 + 33 23+4
(380)
1392+359 577 f75
(5.9)
(220) (1074) ( 1722)
1087k 125 2.5k0.6
(1.30) (1850)* (87)
(47.4) (5.6)
(230) (23) (1 392)
(557)* (1056)
prostanoid excretions, and n o significant changes were found during nifedipine. Plasma prekallikrein decreased (P < 0.05) and urinary kallikrein (P < 0.05) and noradrenaline (P = 0.06) excretions increased during nifedipine treatment. The urinary excretions of kallikrein, catecholamines and prostanoids were also related to creatinine clearance. No essential differences were found when the results were compared with those expressed as daily excretions. In the hypertensive patients of this study the decrease in blood pressure did not correlate with basal levels or changes in prostanoid, catecholamine o r kallikrein excretions nor in plasma prekallikrein. Neither did prostanoid excretions correlate with kallikrein or catecholamine excretions or plasma prekallikrein. No correlations between daily urine sodium and prostanoid excretions were observed. However, in the non-pregnant women there was a correlation between daily urine sodium and PGE, excretions (r, = 0.829, P < 0.05) during nifedipine treatment, but not prior to it.
Discussion PGE,, 6-keto-PGF,, and TXB, in urine are generally considered as indicators of renal prostanoid formation (Seyberth et al. 1988). However, an extrarenal contribution cannot be completely excluded in the urinary excretions of 6-
Table 2. Laboratory parameters in non-pregnant normotensive women before and on the fifth day of nifedipine treatment 10 mg t.i.d. orally.
MeansfS.E.M. (and medians) are given. n=6, * P
