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Summary.

A continuous flow system has been developed to study the endocrine functions of isolated organs. The procedure has been used to investigate the effect of a synthetic gonadotrophin-releasing hormone (Gn-RH) upon the anterior pituitary gland of the adult male rat. A Radiometer blood gas/pH analyser was used to monitor the pH and partial pressures of oxygen and carbon dioxide in the perfusion medium. A series of six experiments with four pituitaries per flask established that the rate of gonadotrophin release under basal conditions was 646±301 (S.D.) ng LH/ml and 404±124 (S.D.) ng FSH/ml. The duration and intensity of the response to Gn-RH was assessed by measuring the areas under the curves according to the trapezoidal rule. A significant increase in the release of FSH and LH was obtained by the administration of 250 ng Gn-RH/ml medium, and dose-response curves were produced for up to 10 μg/ml.

Summary. Isolated pituitary glands from adult male rats were maintained in a continuous flow system. Gn-RH (1000 pmol/ml) caused a characteristic release of cyclic AMP, LH and FSH. Cyclic AMP (1000 nmol/ml) liberated a similar amount of both gonadotrophins. Theophylline (1 mmol/ml) enhanced the effect of cyclic AMP by 21% for LH and 41% for FSH. The infusion of oestradiol (184 pmol/ml) alone or before Gn-RH infusion did not produce a significant effect on the secretion of either gonadotrophin or cyclic AMP. In contrast, there was a significant reduction in the amount of LH (P < 0·025) and FSH (P < 0·05) released by pituitaries infused with oestradiol and cyclic AMP.

Summary. To define a functional difference in Sertoli cells of animals exposed to different photoperiodic conditions, we isolated Sertoli cells from the testes of juvenile Siberian hamsters and cultured them in serum-free medium. In all age groups studied, Sertoli cells isolated from hamsters with delayed and normal puberty responded to follicle-stimulating hormone (FSH) with an increase in lactate production. The increase in lactate production induced by 1000 ng FSH ml⁻¹ was significantly greater in Sertoli cells isolated from hamsters with delayed puberty than in those with normal puberty. These results suggest that Sertoli cells of Siberian hamsters exposed to short photoperiod in vivo may respond to increases in plasma FSH concentrations associated with photostimulation or spontaneous sexual maturation by an increase in secretory activity that may be critical for the initiation of spermatogenesis.

Keywords: Sertoli cells; Siberian hamster; photoperiodism; follicle-stimulating hormone; lactate

In an initial experiment, rabbits were injected i.v. with a platelet-activating factor (PAF) antagonist CV-3988 twice a day on days 5 and 6 of pregnancy. Some inhibition of implantation was observed. This effect could not be reproduced in subsequent experiments at the same or at larger or smaller doses. The non-metabolized analogue of PAF, N-carbamyl-PAF (C-PAF) had an inhibitory effect on implantation only when given at toxic concentrations. When CV-3988 and C-PAF were given together on days 5 and 6, there was no effect on implantation. None of the other PAF antagonists tested – BN52021, SRI63,441, WEB2086 or TCV-309 – at various doses could inhibit implantation when given on the same days of pregnancy. TCV-309, at 0.1 mg kg⁻¹ i.v. given on days 2–4 of pregnancy, was also ineffective. These results provide no clear support for a role of PAF in implantation in rabbits.

In mouse models used to study parturition or pre-clinical therapeutic testing, measurement of uterine contractions is limited to either ex vivo isometric tension or operative intrauterine pressure (IUP). The goal of this study was to: (1) develop a method for transcervical insertion of a pressure catheter to measure in vivo intrauterine contractile pressure during mouse pregnancy, (2) determine whether this method can be utilized numerous times in a single mouse pregnancy without affecting the timing of delivery or fetal outcome and (3) compare the in vivo contractile activity between mouse models of term and preterm labor (PTL). Visualization of the cervix allowed intrauterine pressure catheter (IUPC) placement into anesthetized pregnant mice (plug = day 1, delivery = day 19.5). The amplitude, frequency, duration and area under the curve (AUC) of IUP was lowest on days 16–18, increased significantly (P < 0.05) on the morning of day 19 and reached maximal levels during by the afternoon of day 19 and into the intrapartum period. An AUC threshold of 2.77 mmHg discriminated between inactive labor (day 19 am) and active labor (day 19 pm and intrapartum period). Mice examined on a single vs every experimental timepoint did not have significantly different IUP, timing of delivery, offspring number or fetal/neonatal weight. The IUP was significantly greater in LPS-treated and RU486-treated mouse models of PTL compared to time-matched vehicle control mice. Intrapartum IUP was not significantly different between term and preterm mice. We conclude that utilization of a transcervical IUPC allows sensitive assessment of in vivo uterine contractile activity and labor progression in mouse models without the need for operative approaches.