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Search for other papers by DOREEN V. ILLINGWORTH in
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SUMMARY
The effects of hypophysial stalk-section on the growth and function of the corpus luteum of the non-pregnant guinea-pig have been compared with the effects of hypophysectomy (as previously described) and with the effects of prolactin administered to hypophysectomized animals. Stalk-section soon after ovulation did not impair the growth of the corpora lutea nor their ability to secrete progesterone. Stalk-section before day 9 of the oestrous cycle prevented the normal regression of the corpora lutea; they continued to grow and 3 weeks after ovulation were as large as those of pregnant animals, or of non-pregnant hysterectomized guinea-pigs. The corpora lutea regressed irregularly during the following 2 weeks. When performed on, or later than day 9, stalk-section did not prevent luteal regression at the normal time.
Administration of prolactin (10 i.u./day) to hypophysectomized guinea-pigs restored the growth-rate of the corpora lutea, which reached sizes comparable to those of the normal cycle, and those of stalk-sectioned animals, by 10 days after ovulation.
Our results indicate that prolactin can have substantial luteotrophic activity in the guinea-pig.
Search for other papers by R. DEANESLY in
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Search for other papers by J. S. PERRY in
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SUMMARY
Interruption of the prolonged luteal phase in hysterectomized guinea-pigs, followed by vaginal opening, can be caused by substances affecting the hypothalamus and hypophysis, which check gonadotrophin output. In the present experiments, both progesterone and reserpine were effective and caused regression of the corpora lutea. It may be concluded that in the guinea-pig, as in the sow and the sheep, the corpora lutea of hysterectomy do not function independently of the hypophysis.
The uterine factor associated with normal cyclic corpora lutea regression, which is lacking after hysterectomy, presumably acts on the hypophysis rather than directly on the corpora lutea.
Search for other papers by DOREEN V. ILLINGWORTH in
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Search for other papers by R. B. HEAP in
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Search for other papers by J. S. PERRY in
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SUMMARY
The metabolic clearance rate (MCR) of progesterone was measured by continuous infusion of the tritium-labelled steroid in guinea-pigs under light sodium pentobarbitone anaesthesia. In normal animals during the oestrous cycle, the MCR was 112·8 ± 7·0 (s.e.) 1 plasma/day/kg. In pregnant animals there was a sharp decrease in MCR between days 15 and 20, to 8·3 ± 0·8 1/day/kg. This low clearance rate was observed throughout the remainder of gestation. After parturition MCR returned slowly to non-pregnant levels, reaching 85 1/day/kg by day 12 post partum.
The decrease in metabolic clearance rate occurred at the same time as the increase in plasma concentration of progesterone. This may be related to an increase in binding proteins with a high affinity for progesterone. The stimulus for the decrease in MCR in pregnancy is obscure but appears to depend on the presence of a viable conceptus. In the non-pregnant guinea-pig the MCR is not reduced by exogenous oestrogen, hysterectomy or hypophysectomy.
Search for other papers by D. L. Economides in
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Search for other papers by R. J. S. Howell in
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Search for other papers by I. Gilbert in
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Search for other papers by L. A. Perry in
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Search for other papers by T. Chard in
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ABSTRACT
Blood was taken from three healthy female and three healthy male volunteers every 20 s for 15 min. The serum level of oestradiol was measured and the pattern of variation assessed by a cusum plot of the sequential data, by autocorrelation of the detrended serial data, and by looking for pulses. In two cases the variation in oestradiol values was greater than that which could be attributed to variation in the assay. Both these subjects showed a significant overall change in values during the sampling period (an increase and a decrease). There was no trend in the remaining four subjects. In two of the six subjects there was significant autocorrelation of detrended sequential levels. Defining a 'pulse' as three times the assay coefficient of variation no more pulses were identified than was expected from random fluctuations. By frequency analysis the two subjects with significant autocorrelation showed periodic fluctuations of approximately 70/h and 9/h respectively. It is apparent that both the rate of sampling and the method of analysis greatly influence the evaluation of pulsatile release of oestradiol.
J. Endocr. (1988) 118, 161–165
Search for other papers by DOREEN V. ILLINGWORTH in
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Search for other papers by J. S. PERRY in
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Search for other papers by NICOLA ACKLAND in
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Search for other papers by ANGELA M. BURTON in
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SUMMARY
Pregnancy was sustained to term (>63 days) in 15 out of a total of 46 guinea-pigs, hypophysectomized within 4 days after mating. The majority (22/29) of complete or partial abortions occurred between 20 and 35 days post coitum. Analysis of plasma samples showed that the pregnant hypophysectomized animals with live foetuses had high progesterone and progesterone-binding protein concentrations, equivalent to those found in intact pregnant guinea-pigs. Animals that received daily injections of cortisone acetate from day 55 (7/15) gave birth to live young at the normal time (67–68 days). Plasma samples from one animal taken during parturition showed no measurable oxytocin in maternal plasma, but oxytocin was present in foetal plasma at the moment of birth.
Search for other papers by H. S. Wang in
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Search for other papers by L. A. Perry in
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Search for other papers by J. Kanisius in
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Search for other papers by R. K. Iles in
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Search for other papers by J. M. P. Holly in
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Search for other papers by T. Chard in
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ABSTRACT
Insulin-like growth factor-binding protein-1 (IGFBP-1) has been purified from amniotic fluid by anion exchange, hydrophobic interaction and gel filtration chromatography. The overall recovery of the purification process was 12·2%. The purified IGFBP-1 yielded a single band on SDS-PAGE gel but showed two bands (34 kDa and 68 kDa) on Western blot under non-reducing conditions. Polyclonal antisera were raised by immunization of sheep using the purified IGFBP-1. The best antiserum bound 50% of 125I-labelled IGFBP-1 at a final dilution of 1:500 000. A radioimmunoassay for IGFBP-1 was developed. This assay had a minimum detection limit of 5 μg/1, and was used to determine serum levels in non-pregnant and pregnant women. There was no cross-reaction with a wide variety of materials tested. Serum IGFBP-1 levels in non-pregnant individuals (33±16 (s.D.) μg/1) were found to be significantly lower than those in the second (96±64 μg/1) and third trimesters (95 ±60 μg/1) of pregnant women. During pregnancy, circulating IGFBP-1 levels increased rapidly in the first trimester and reached a peak at 12–13 weeks of gestation (107±75 μg/l). The level then remained at 80±53 to 103±70 μg/l until term.
Journal of Endocrinology (1991) 128, 161–168
Search for other papers by D. V. ILLINGWORTH in
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Search for other papers by J. R. G. CHALLIS in
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Search for other papers by N. ACKLAND in
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Search for other papers by A. M. BURTON in
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Search for other papers by R. B. HEAP in
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Search for other papers by J. S. PERRY in
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SUMMARY
Parturition in the guinea-pig is not preceded by any consistent change in the maternal plasma concentrations of progesterone, total unconjugated oestrogens or corticosteroids, or by a significant change in the concentration of progesterone-binding globulin (PBG). The onset of parturition was delayed by high doses of oestrogens (stilboestrol and oestradiol), but was not affected by oestriol or an antiserum raised against oestradiol. Premature parturition was achieved by the intra-carotid infusion of adrenocorticotrophin or prostaglandins (PGF2α, PGE2, I.C.I. 80,996) in conscious animals with indwelling catheters. I.C.I. 80,996, a potent analogue of PGF2α, induced parturition in all seven guinea-pigs treated; delivery occurred within 6 h of starting the infusion in six animals, and within 48 h in the seventh. The undesirable side-effects that accompanied treatment with PGF2α or PGE2 were not encountered with I.C.I. 80,996. Parturition induced experimentally resembled normal delivery but was not preceded by any significant change in the maternal levels of progesterone, total unconjugated oestrogens, corticosteroids, PBG or CBG in the circulation. Oxytocin was not detected until the delivery of the first foetus.
Parturition was not induced by maternal or foetal injections of corticosteroids or dexamethasone. Earlier findings are confirmed that the foetal adrenal grows steadily throughout late pregnancy and, unlike the foetal lamb adrenal, undergoes no rapid phase of growth immediately before term. Foetal adrenal weight decreased relative to foetal body weight.
The trigger for parturition in this species remains unidentified.
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Search for other papers by J. V. Anderson in
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Search for other papers by C. Volta in
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Search for other papers by L. Perry in
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Search for other papers by P. L. Drury in
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Search for other papers by S. R. Bloom in
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Search for other papers by G. M. Besser in
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Search for other papers by A. Grossman in
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ABSTRACT
The effect of two analogues of [Met]-enkephalin, [d-Ala2,N-Phe4,Met(0)-ol5]-enkephalin and its guanyl derivative, on plasma concentrations of atrial natriuretic peptide (ANP) and serum aldosterone in six normal subjects was investigated. All subjects were given a 1 litre water load to inhibit vasopressin release. Both analogues, when injected i.v. at a dose of 100 μg, stimulated release of prolactin and GH and inhibited serum cortisol; there was no significant change in blood pressure, pulse rate or urine output. Neither plasma concentrations of ANP nor serum aldosterone levels changed significantly after injection of either analogue at a low or high dose. Naloxone, given i.v. as an 8 mg bolus, also failed to alter concentrations of either ANP or aldosterone, while it significantly stimulated the release of serum LH and cortisol. It was concluded that under basal conditions opiate receptors are unable to modulate plasma ANP or serum aldosterone concentrations.
J. Endocr. (1988) 116, 313–317
