ABSTRACT

We have measured fetal and maternal plasma concentrations of cortisol, prolactin, GH and glucose in samples collected during a 24-h period in 14 animals between 127 and 142 days of gestation. There was a significant increase in both the mean daily plasma cortisol concentration and mean daily coefficient of variation (C.V.) of plasma cortisol concentrations after 135 days of gestation. There was also a significant variation in the fetal plasma cortisol concentrations with a peak occurring at 19.00 h. There was a significant sinusoidal diurnal rhythm in the plasma prolactin concentrations in both the fetal sheep and pregnant ewe and the maximal prolactin concentrations occurred between 19.00 and 23.00 h (fetal) and 21.00 and 01.00 h (maternal). Although no significant diurnal variation was detected in fetal plasma GH concentrations, there was a significant sinusoidal diurnal rhythm in the plasma GH concentrations of the pregnant ewe and the maximal maternal GH concentrations occurred between 21.00 and 01.00 h. Both the fetal and maternal plasma glucose concentrations showed a significant sinusoidal diurnal rhythm. The maximal maternal and fetal glucose concentrations were measured between 21.00 and 01.00 h and between 23.00 and 03.00 h respectively. We have therefore established that diurnal variations in plasma cortisol and prolactin concentrations exist prenatally. Whether the presence of such hormonal rhythms reflects the activity of an endogenous fetal circadian pacemaker remains to be established.

J. Endocr. (1987) 114, 65–72

Abstract

It has been shown that restricting food in lactating rats for the first 2 weeks postpartum at a level of 60% of the ad-libitum daily ration increases the length of lactational dioestrus by about 7 days but little is known about correlated changes in hormone levels. In the first experiment we report changes in LH, prolactin (PRL) and ACTH secretion in food-restricted and ad-libitum fed lactating rats at various stages of lactation. Our results demonstrate that food restriction during the first 2 weeks of lactation did not affect PRL or ACTH secretion, but decreased plasma LH levels despite comparable GnRH receptor density between food-restricted and ad-libitum fed females. In the second experiments we investigated a possible causal relationship between the increased secretion of progesterone seen in food-restricted females and the suppression of plasma LH levels, by determining the effects of bromocryptine treatment and ovariectomy on LH secretion in both ad-libitum fed and food-restricted lactating females. LH suppression in food-restricted lactating females was not affected by ovariectomy or bromocryptine treatment, although the latter treatment significantly increased GnRH receptor number. These data suggest that factors other than ovarian steroids, PRL or increased adrenocortical activity modulate LH secretion and the length of lactational dioestrus in food-restricted lactating females.

Journal of Endocrinology (1995) 146, 95–104

ABSTRACT

Bovine adrenal cortex tissue expresses high levels of glutathione S-transferase (GST) from each of the α, μ and π gene families. We describe the purification and characterization of an abundant α-class GST from this tissue that has not been identified previously because of its failure to bind to S-hexylglutathione–Sepharose 6B (S-hexG-Ag). This enzyme has been affinity purified on glutathione–Sepharose 6B (GSH-Ag) and was obtained in a highly purified form by employing S-hexG-Ag to remove the bulk of GST before chromatography on GSH-Ag. The purified GST eluted from GSH-Ag was found to exhibit marked peroxidase and Δ⁵-ketosteroid isomerase activities (19·2 and 1·67 U/mg respectively). The bovine enzyme also showed high GST activity towards 4-hydroxynonenal (5·09 U/mg). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the bovine GST contains two distinct polypeptides, one with an M _r of 25 900 and the other with an M _r of 26 500.

An abundant α-class GST was also purified from human adrenal cortex that possessed properties which were similar to the bovine α-class GST described above; however, unlike the bovine enzyme, the corresponding human α-class GST bound to S-hexG-Ag. As with the bovine enzyme, the purified human GST displayed marked peroxidase and isomerase activities (27 and 4·02 U/mg respectively). Further analysis on SDS-PAGE (M _r 25 800) and reverse-phase highperformance liquid chromatography established that this abundant α-class GST in human adrenal cortex is equivalent to the human liver GST B₁B₁ enzyme.

As both human and bovine adrenal cortex contain high levels of α-class GST with similar catalytic properties, we discuss the possible functions of these enzymes in this tissue.

Journal of Endocrinology (1992) 132, 83–92

ABSTRACT

Young, growing rats which had been chronically (2 weeks) adrenalectomized or parathyroidectomized were used to define the roles of the adrenal and parathyroid glands on the maintenance of normal circadian rhythms of DNA, collagen and non-collagen protein synthesis in the skeleton. The animals were conditioned to food being available ad libitum and to 12 h light: 12 h darkness (lights on from 08.00 to 20.00 h). The pace of DNA, collagen and non-collagen protein synthesis in different regions of the tibia (tibial growth cartilage, metaphysial bone and diaphysial bone) was measured by the in-vivo incorporation of tritiated thymidine (1 h) and radioactive proline (48 h). In intact rats there were no regional differences in the phasing of the circadian profiles; peak DNA and non-collagen protein synthesis occurred at the onset of the dark period while peak collagen synthesis occurred during the middle of the period of light. Adrenalectomy selectively abolished the regional DNA synthesis rhythms without altering the phases of the serum Ca and phosphorus (P) rhythms, which peak at mid-day and at the onset of darkness respectively. Parathyroidectomy abolished the regional rhythms for collagen and non-collagen protein synthesis and serum Ca rhythms, without altering the phase of the serum P and corticosterone rhythms. Dietary Ca-lactate supplements, which raised serum Ca levels towards normal in parathyroidectomized rats, were able to correct serum corticosterone values but did not normalize bone collagen and non-collagen protein synthesis values. These data indicate that the adrenal rhythm governs the proliferative activities of bone and cartilage cells, and that parathyroid hormone is essential to maintain normal collagen and non-collagen protein synthesis rhythms.

J. Endocr. (1984) 103, 49–57

Placental progesterone synthesis exposes the fetus to high levels of progesterone and progesterone metabolites during late gestation which may influence fetal behaviour. To determine the role of maternal progesterone synthesis in the control of fetal arousal state and fetal breathing movements (FBM), the effect of raising and lowering maternal progesterone concentrations was examined in chronically catheterised fetal sheep. Fetal and maternal vascular catheters, fetal tracheal and amniotic fluid catheters as well as electrodes for recording fetal electrocortical (ECoG), electro-ocular (EOG) and nuchal muscle electromyographic (EMG) activity were implanted between 118 and 122 days gestational age (GA). Progesterone, 100 mg, administered twice daily i.m. for 3 days (130–133 days GA) resulted in a marked elevation in maternal plasma progesterone concentrations (370 ± 121%, n=5, P<0·05), but had no effect on fetal plasma concentrations. Fetal EOG episodes and the duration of fetal behavioural arousal were significantly suppressed throughout the progesterone treatment period (74·4–81·1% and 58–65% respectively, P<0·05, n=5). Four ewes received Trilostane (25 mg i.v.), a 3β-hydroxysteroid dehydrogenase inhibitor, between 136 and 140 days GA. Maternal and fetal progesterone concentrations were significantly lowered by 60 min after treatment (19·8 ± 8·0% and 39·5 ± 24·3% respectively, P<0·05). The incidence of fetal EOG activity increased from a pretreatment level of 26·8 ± 1·5 min/h to 30·3 ± 2·8 min/h at 1–6 h and to 35·0 ± 1·7 min/h (P<0·05) during the 7–12 h after Trilostane treatment. The duration of FBM episodes was significantly higher at 1–6 h and 7–12 h after Trilostane treatment (19·5 ± 3·0 and 23·6 ± 5·5 min/h respectively, P<0·05) compared with pretreatment levels (11·2 ± 1·2 min/h). We conclude that increasing maternal progesterone levels suppresses fetal EOG activity and behavioural arousal, whereas reducing maternal progesterone synthesis leads to an elevation of EOG activity and FBM.

Journal of Endocrinology (1997) 152, 379–386

ABSTRACT

Salivary progesterone concentrations were measured in daily samples collected between 08.00 and 09.00 h throughout the menstrual cycle of women with a history of fertility. The luteal-phase salivary progesterone profiles in these normally menstruating, healthy women were characterized using a computer program based on a cumulative sum procedure. This method of statistical analysis led to the development of a 'progesterone boundary diagram', the inner and outer domains of which distinguished between the profiles of salivary progesterone considered compatible with fertility, and those observed in subfertile women attending an infertility clinic.

J. Endocr. (1985) 104, 441–446

ABSTRACT

We have examined the activation of the pituitary-adrenal axis in two lines of rats, the Roman high (RHA)- and low (RLA)-avoidance rats known to be emotionally different. These rats are selected for rapid acquisition of a conditioned avoidance response (RHA) compared with failure to acquire this response (RLA). In this study the endocrine response (ACTH, corticosterone, aldosterone) of RLA and RHA rats to two types of stress was examined: exposure to openfield stress for 10 min (Op) or exposure to ether vapours for 3 min (E). Basal plasma ACTH concentrations were lower in RLA than in RHA rats (RLA: 110·8 ± 24·5 ng/l; RHA: 252·7 ± 60·8 ng/l, P<0·05) but the absolute values of ACTH reached after both types of stress were comparable between RLA and RHA rats. Plasma corticosterone and aldosterone under resting conditions were not different between RLA and RHA rats. Plasma corticosterone was higher in RLA following openfield stress (P<0·05) while no differences between RLA and RHA were observed after ether stress (RHA: basal = 66±14·nmol/l, Op =384± 55, E= 606± 75; RLA: basal=121±52, Op = 612 ±92, E= 698 ± 89). Stressinduced increases in plasma aldosterone were higher in the RLA line after both types of stress (RHA: basal = 175±36 pmol/l, Op = 546±53, E= 563± 47; RLA: basal = 272 ± 64, Op =1246 ± 91, E= 863 ± 72). Pituitary responsiveness to exogenous corticotrophinreleasing factor (CRF) in vivo and in vitro differed in the two lines: administration of ovine CRF (10 μg/kg body weight, i.p.) resulted in significant increases in ACTH secretion but the response was significantly lower in RHA rats (RHA: 511·1 ±41·5 ng/l; RLA: 831·4 ± 70·3 ng/l, P<0·01). Dispersed pituitary cells from the RHA line exhibited a smaller response to CRF (10 nmol/l) treatment in vitro compared with cells derived from the RLA rats (RHA: 750 ± 83% of control; RLA: 1374 ±79, P<0·01) suggesting differences in pituitary sensitivity to CRF between the two lines. Additional differences at the pituitary level were observed since the type II glucocorticoid receptor population in RHA rats was higher than in RLA rats (RHA: 246±13 fmol [³H]RU28362 bound/mg protein; RLA: 173±18, P<0·01). Similarly, hippocampal type I glucocorticoid receptor population was increased in RHA rats (RHA: 172·2 ± 8·3 fmol [³H]aldosterone bound/mg protein; RLA: 116·7±7·3, P< 0·01). It is concluded that first, differences in pituitary activity between RLA and RHA rats are distinct from changes observed at the adrenal level, secondly, increased stress-induced ACTH output in the RLA line is associated with enhanced pituitary sensitivity to CRF and possibly with diminished corticosterone inhibitory feedback action on CRF and ACTH secretion, and thirdly, the possible involvement of differences in the pattern of CRF secretion between RLA and RHA rats on resting pituitary ACTH secretion cannot be excluded.

Journal of Endocrinology (1989) 123, 477–485

ABSTRACT

Abnormal ratios of testosterone to epitestosterone (T/E) and testosterone to LH (T/LH) in the urine of male athletes are indicative of testosterone administration. The T/E ratio has been adopted by the International Olympic Committee as the sole criterion used in the detection of testosterone administration. An athlete is usually considered to have failed a drug test if the urinary T/E ratio is greater than 6. Human chorionic gonadotrophin (hCG) has been used by some male athletes to stimulate testicular secretion of testosterone. The purpose of this investigation was to examine whether the urinary T/E ratio can remain unaffected by administration of hCG to normal adult males. Administration of hCG resulted in large increases in serum testosterone concentrations and urinary T/LH ratios but small changes in urinary T/E ratios of two subjects (maximum T/E values observed were 0·8 and 1·2 respectively). These observations suggest that the urinary T/LH ratio is a valuable indicator of hCG as well as of testosterone administration. This study is the first to measure urinary T/LH ratios using the technique of gas chromatography–mass spectrometry for quantification of testosterone, and highly specific monoclonal antibodies for the measurement of LH. An ultrafiltration method is proposed as part of a confirmatory procedure to be adopted in the measurement of urinary gonadotrophins for drug control in sport.

Journal of Endocrinology (1991) 131, 147–154

Most techniques for determining cortisol binding characteristics of transcortin and albumin involve disturbance of the equilibrium between cortisol and binding protein. Only ultrafiltration of undiluted plasma with temperature and pH control allows binding constants to be measured under near physiological conditions. Equilibrium dialysis is convenient and widely used for investigating cortisol binding but the interpretation of data has been the subject of controversy (Mills, 1962; Tait & Burstein, 1964). The standard method of calculation (Slaunwhite & Sandberg, 1959) is valid only when related to the final equilibrium position. The derived binding constants refer to cortisol and transcortin concentrations within the sac at the end of dialysis which often differ greatly from those in the original plasma.

We describe here a simple method for treatment of dialysis data which, with appropriate correction for dilution, yields binding constants in close accord with those obtained by ultrafiltration of undiluted plasma.

Plasmas containing labelled

IGF-I expression has been observed in human uterine leiomyomas. To examine whether autocrine IGF-I signaling plays a role in the growth of these tumors, we used an animal model of uterine leiomyoma (the Eker rat) to investigate regulation of IGF-I and the IGF-I receptor (IGF-IR) expression in tumors and normal myometrium. During the normal estrous cycle, myometrial IGF-I expression peaked on the day of proestrus when the rate of proliferation in this tissue is greatest. In leiomyomas, the expression of IGF-I was increased 7.5-fold compared with the age-matched normal tissue. The level of IGF-IR mRNA in both tumor and non-tumor tissues was found to inversely correlate with that of IGF-I. Changes observed in IGF-I signaling components correlated with the activation state of the signal-transducing protein insulin receptor substrate-1 (IRS-1). During diestrus and proestrus when IGF-I levels were increasing, tyrosine phosphorylation of IRS-1 was increased up to 5.7-fold in the normal myometrium relative to estrus, when IGF-I levels were the lowest. Additionally, IRS-1 phosphorylation was 4-fold greater in leiomyomas relative to age-matched normal myometrium. Autocrine stimulation of the IGF-IR may, therefore, play a role in regulating the normal growth of the myometrium, and dysregulation of IGF-I signaling could contribute to the neoplastic growth of uterine leiomyomas.