Veterinary Medical Research Institute and Department of Veterinary Clinical Sciences, Iowa State University, Ames, Iowa 50010, USA
BOVINE PLASMA OESTROGENS, PROGESTERONE AND GLUCOCORTICOIDS DURING
DEXAMETHASONE INDUCED PARTURITION
By L. E. Evans and W. C.
Wagner
ABSTRACT Plasma samples were collected from jugular, uterine and utero-ovarian veins during glucocorticoid induced parturition. Plasma oestrogens, corticosteroids and progesterone were determined by competitive protein binding methods. Corticosteroids and progesterone began to decline within 8 to 10 h following DXMS treatment. Corticoids were only temporarily suppressed, while progesterone fell to minimum levels and remained low through
calving. At this stage of gestation (270 days) peripheral plasma progesterone was primarily of ovarian origin. Pre-treatment with HCG appeared to support progesterone production by the CL despite DXMS treatment in 2 of 6 cows. These 2 cows failed to calve within the expected 96 h after DXMS. Plasma oestrogens did not show significant increases until 24 h after DXMS treatment. Cows which responded to DXMS treatment (calved) had significantly higher oestrogen levels than those which did not respond. It was concluded that oestrogens probably play a permissive rather than an initiating role in parturition.
Parturition can be effectively induced in late gestation in the ewe (Bosc 1972) and cow (Adams 8c Wagner 1970) with appropriate doses of glucocorticoids. This has proven to be a useful tool in the study of physiological mechanisms controlling parturition, particularly the temporal changes in maternal or foetal plasma steroids at parturition.
A
precipitous drop
in
peripheral plasma progesterone
occurs
approximately
48 h prior to parturition in the cow (Stabenfeldt et al. 1970; Smith et al. 1973). A similar decline occurs in glucocorticoid induced parturition (Wright et al. 1970; Edqvist et al. 1972). Parturition can be delayed by progesterone ad¬ ministration (Jochle et al. 1972) and generally hastened by oophorectomy (McDonald et al. 1953) leading to speculation that the ovary is a primary source of progesterone for pregnancy maintenance. Oestrogens in both urine (Mellin et al. 1966) and plasma (Smith et al. 1973; Edqvist et al. 1973) have been shown to increase near parturition and to decline rapidly after delivery in the cow. Peripheral plasma corticosteroids have also been studied in natural and induced calving (Adams 8c Wagner 1970; Smith et al. 1973). Corticoids follow a general pattern of increase in the last 7-10 days of pregnancy and rapid increase at parturition. Since these changes in peripheral plasma steroids follow a definite pattern in both natural and induced parturition, this investigation was directed toward the sequential changes and interrelations of hormone levels at parturition.
MATERIALS AND METHODS Seven Holstein and 6 Hereford cows in late gestation were used in two experimental groups. They were confined to stanchions until calving and fed hay and concentrates sufficient to maintain good body weight.
Group
1
mg of dexamethasone (DXMS) were administered intramuscularly to 6 Holstein cows at about 268 days gestation. The other Holstein cow was allowed to calve naturally as a control cow. Indwelling vinyl catheters (1.47 mm ID x 2.03 mm OD) were placed in the jugular vein of each cow. Heparinized blood was collected at 8 h intervals for 2 to 5 days prior to DXMS treatment. Immediately prior to DXMS, indwelling vinyl catheters (0.86 mm ID x 1.35 mm OD) were inserted via laparotomy in the anterior uterine vein of the pregnant horn in 4 cows. Catheters were positioned distal to the ovary for collection of only uterine blood and proximal to the ovary for collection of both uterine and ovarian venous effluent. Heparinized blood samples were collected from all sample sites hourly for 96 h following surgery and DXMS or until parturition.
Twenty
Group
2 Six Hereford cows in late gestation were catheterized in the jugular vein only. Samples were collected every 8 h until parturition. After the first 24 h sample period the 6 cows were treated with 1000 units of human chorionic gonadotrophin (HCG) at each sample collection for 3 days. Twenty mg DXMS was administered at the beginning of the second day of HCG treatment. Plasma samples were assayed for plasma progesterone and oestrogen content but corticoid levels were not determined.
All blood samples were chilled, the plasma harvested and stored at -20°C until for steroid content. Samples collected nearest parturition were designated as 0 hour. Plasma progesterone was determined by a competitive protein binding method as described by Neill et al. (1967) and modified by Wagner et al. (1972). Ether extracts were purified on thin-layer chromatograms and corrected for procedural losses by the quantitative recovery of radioactive progesterone. Oestrone and oestradiol were assayed by radio-ligand techniques using rabbit uterine cytosol as the binding protein (Korenman et al. 1970). The slightly modified procedure used was previously described by Molokwu Se Wagner (1973). The competitive protein binding method described by Murphy (1967) and modified by Whipp Se Lyon (1970) was used to assay the total corticosteroid content of plasma
assayed
samples. Sample means calculated from 8 h sample values were subjected to statistical analysis. Mean differences were tested for significance by least squares analysis of variance as described by Kempthorne (1952) with allowance for unequal sub-class numbers as described by Harvey (1960).
20h
Jugular plasma
corticoids
(ng/ml,
Fig.
1.
± se) in DXMS treated and after parturition. mean
cows
(n 3) =
before
RESULTS
Group
1
a. Corticosleroids. Jugular plasma corticosteroids were significantly de¬ pressed (P < 0.05) within 12 h after DXMS treatment (Fig. 1). Pre-surgical levels ranged from 5 to 12 ng/ml while samples taken immediately postsurgery (day-2) were consistently higher (17 ng/ml). DXMS treatment after surgery depressed plasma corticosteroids for 1 to 3 days in all cows, although some individuals showed a moderate increase within the last 16 h prior to parturition. A similar increase was observed in the control cow at the time of parturition (Fig. 2). -
Comparisons after significant difference
surgery and DXMS in 2 cows showed there in venous plasma corticosteroids between the uterine, and utero-ovarian sample sites.
-4
-3
-2
-1
0
+1
Days
Jugular plasma
corticoids
Fig. 2. (ng/ml) in naturally calving
cow
20.
was
no
jugular,
A
\ \/
\/ DXMS(C) -
.
Natural
calving
DXMS(NC)
-7
-1
Fig. Jugular plasma progesterone (ng/ml) in DXMS treated calving, and in naturally calving 3.
cows
(C) calving, (NC)
not
cow.
Jugular Uterine Utero-ovarian
Fig.
4.
Plasma progesterone (ng/ml) in jugular, utero-ovarian and uterine veins of DXMS treated cows (n 4). First utero-ovarian and uterine samples were collected (O) just prior to DXMS treatment. =
Peripheral plasma progesterone levels in DXMS treated control cow are shown in Fig. 3. Pre-treatment levels averaged 5.8 ng/ml in the 5 cows which calved within 48 h after DXMS. Progesterone levels declined rapidly to 1.6 ng/ml prior to calving. In the control cow a similar pattern of decline occurred during the final 48 h prior to calving. In contrast, progesterone levels in one non-responding cow declined only slightly from 6 ng/ml before to 4.6 ng/ml 72 h after DXMS. This cow calved normally 12 days after DXMS. Plasma samples were collected hourly from three sample sites following surgery. Plasma progesterone levels in the uterine, utero-ovarian and jugular plasma of 4 cows following surgery and DXMS are shown in Fig. 4. Uteroovarian vein levels were significantly greater (/,
BOVINE PLASMA OESTROGENS, PROGESTERONE AND GLUCOCORTICOIDS DURING
DEXAMETHASONE INDUCED PARTURITION
By L. E. Evans and W. C.
Wagner
ABSTRACT Plasma samples were collected from jugular, uterine and utero-ovarian veins during glucocorticoid induced parturition. Plasma oestrogens, corticosteroids and progesterone were determined by competitive protein binding methods. Corticosteroids and progesterone began to decline within 8 to 10 h following DXMS treatment. Corticoids were only temporarily suppressed, while progesterone fell to minimum levels and remained low through
calving. At this stage of gestation (270 days) peripheral plasma progesterone was primarily of ovarian origin. Pre-treatment with HCG appeared to support progesterone production by the CL despite DXMS treatment in 2 of 6 cows. These 2 cows failed to calve within the expected 96 h after DXMS. Plasma oestrogens did not show significant increases until 24 h after DXMS treatment. Cows which responded to DXMS treatment (calved) had significantly higher oestrogen levels than those which did not respond. It was concluded that oestrogens probably play a permissive rather than an initiating role in parturition.
Parturition can be effectively induced in late gestation in the ewe (Bosc 1972) and cow (Adams 8c Wagner 1970) with appropriate doses of glucocorticoids. This has proven to be a useful tool in the study of physiological mechanisms controlling parturition, particularly the temporal changes in maternal or foetal plasma steroids at parturition.
A
precipitous drop
in
peripheral plasma progesterone
occurs
approximately
48 h prior to parturition in the cow (Stabenfeldt et al. 1970; Smith et al. 1973). A similar decline occurs in glucocorticoid induced parturition (Wright et al. 1970; Edqvist et al. 1972). Parturition can be delayed by progesterone ad¬ ministration (Jochle et al. 1972) and generally hastened by oophorectomy (McDonald et al. 1953) leading to speculation that the ovary is a primary source of progesterone for pregnancy maintenance. Oestrogens in both urine (Mellin et al. 1966) and plasma (Smith et al. 1973; Edqvist et al. 1973) have been shown to increase near parturition and to decline rapidly after delivery in the cow. Peripheral plasma corticosteroids have also been studied in natural and induced calving (Adams 8c Wagner 1970; Smith et al. 1973). Corticoids follow a general pattern of increase in the last 7-10 days of pregnancy and rapid increase at parturition. Since these changes in peripheral plasma steroids follow a definite pattern in both natural and induced parturition, this investigation was directed toward the sequential changes and interrelations of hormone levels at parturition.
MATERIALS AND METHODS Seven Holstein and 6 Hereford cows in late gestation were used in two experimental groups. They were confined to stanchions until calving and fed hay and concentrates sufficient to maintain good body weight.
Group
1
mg of dexamethasone (DXMS) were administered intramuscularly to 6 Holstein cows at about 268 days gestation. The other Holstein cow was allowed to calve naturally as a control cow. Indwelling vinyl catheters (1.47 mm ID x 2.03 mm OD) were placed in the jugular vein of each cow. Heparinized blood was collected at 8 h intervals for 2 to 5 days prior to DXMS treatment. Immediately prior to DXMS, indwelling vinyl catheters (0.86 mm ID x 1.35 mm OD) were inserted via laparotomy in the anterior uterine vein of the pregnant horn in 4 cows. Catheters were positioned distal to the ovary for collection of only uterine blood and proximal to the ovary for collection of both uterine and ovarian venous effluent. Heparinized blood samples were collected from all sample sites hourly for 96 h following surgery and DXMS or until parturition.
Twenty
Group
2 Six Hereford cows in late gestation were catheterized in the jugular vein only. Samples were collected every 8 h until parturition. After the first 24 h sample period the 6 cows were treated with 1000 units of human chorionic gonadotrophin (HCG) at each sample collection for 3 days. Twenty mg DXMS was administered at the beginning of the second day of HCG treatment. Plasma samples were assayed for plasma progesterone and oestrogen content but corticoid levels were not determined.
All blood samples were chilled, the plasma harvested and stored at -20°C until for steroid content. Samples collected nearest parturition were designated as 0 hour. Plasma progesterone was determined by a competitive protein binding method as described by Neill et al. (1967) and modified by Wagner et al. (1972). Ether extracts were purified on thin-layer chromatograms and corrected for procedural losses by the quantitative recovery of radioactive progesterone. Oestrone and oestradiol were assayed by radio-ligand techniques using rabbit uterine cytosol as the binding protein (Korenman et al. 1970). The slightly modified procedure used was previously described by Molokwu Se Wagner (1973). The competitive protein binding method described by Murphy (1967) and modified by Whipp Se Lyon (1970) was used to assay the total corticosteroid content of plasma
assayed
samples. Sample means calculated from 8 h sample values were subjected to statistical analysis. Mean differences were tested for significance by least squares analysis of variance as described by Kempthorne (1952) with allowance for unequal sub-class numbers as described by Harvey (1960).
20h
Jugular plasma
corticoids
(ng/ml,
Fig.
1.
± se) in DXMS treated and after parturition. mean
cows
(n 3) =
before
RESULTS
Group
1
a. Corticosleroids. Jugular plasma corticosteroids were significantly de¬ pressed (P < 0.05) within 12 h after DXMS treatment (Fig. 1). Pre-surgical levels ranged from 5 to 12 ng/ml while samples taken immediately postsurgery (day-2) were consistently higher (17 ng/ml). DXMS treatment after surgery depressed plasma corticosteroids for 1 to 3 days in all cows, although some individuals showed a moderate increase within the last 16 h prior to parturition. A similar increase was observed in the control cow at the time of parturition (Fig. 2). -
Comparisons after significant difference
surgery and DXMS in 2 cows showed there in venous plasma corticosteroids between the uterine, and utero-ovarian sample sites.
-4
-3
-2
-1
0
+1
Days
Jugular plasma
corticoids
Fig. 2. (ng/ml) in naturally calving
cow
20.
was
no
jugular,
A
\ \/
\/ DXMS(C) -
.
Natural
calving
DXMS(NC)
-7
-1
Fig. Jugular plasma progesterone (ng/ml) in DXMS treated calving, and in naturally calving 3.
cows
(C) calving, (NC)
not
cow.
Jugular Uterine Utero-ovarian
Fig.
4.
Plasma progesterone (ng/ml) in jugular, utero-ovarian and uterine veins of DXMS treated cows (n 4). First utero-ovarian and uterine samples were collected (O) just prior to DXMS treatment. =
Peripheral plasma progesterone levels in DXMS treated control cow are shown in Fig. 3. Pre-treatment levels averaged 5.8 ng/ml in the 5 cows which calved within 48 h after DXMS. Progesterone levels declined rapidly to 1.6 ng/ml prior to calving. In the control cow a similar pattern of decline occurred during the final 48 h prior to calving. In contrast, progesterone levels in one non-responding cow declined only slightly from 6 ng/ml before to 4.6 ng/ml 72 h after DXMS. This cow calved normally 12 days after DXMS. Plasma samples were collected hourly from three sample sites following surgery. Plasma progesterone levels in the uterine, utero-ovarian and jugular plasma of 4 cows following surgery and DXMS are shown in Fig. 4. Uteroovarian vein levels were significantly greater (/,
