Barrie J. Hodgson

Effect of estrogen and progesterone on the time-course of tubal ovum transport in rabbits

Abstract Experiments were designed to establish the detailed time-course of ovum transport through the rabbit oviduct, as well as the sites at which estrogen and progesterone exert their effects on egg transport. Whole oviducts were cleared in benzyl benzoate, and the eggs located in situ. Histologic sections were cut distal and proximal to each egg or egg cluster, in order to locate the eggs anatomically (isthmus, ampulla, or ampullary-isthmic junction). The microscopic anatomy was then correlated with the per cent of the distance from the fimbria to the uterotubal junction traversed by the ova. The pause of ova at the ampullary-isthmic junction seen in the controls was prolonged by estrogen. Progesterone, in contrast, seemed to exert its influence at both the ampullary-isthmic junction and the proximal isthmus. Ova were never found in the 10 per cent of the oviduct closer to the uterotubal junction.

Accelerated ovum transport in rabbits induced by endotoxin 1. Changes in prostaglandin levels and reversal of endotoxin effect

Abstract The effect of endotoxin ( Salmonella enteritidis -Boivin) on ovum transport in the rabbit was examined. A dose of 10 μg/kg intravenously (iv) given 24 h after an injection of human chorionic gonadotrophin (hCG) to induce ovulation caused expulsion of 87% of ova from the oviduct within 24 h. The ED50 and 95% probability limits were 3.1 (2.38–4.03) μg/kg. A dose of 20 μg/kg given at 24 h after hCG exerted its effect on ovum transport within 4 h. Concurrent treatment with indomethacin completely prevented the effect of endotoxin on ovum transport. Endotoxin caused an increase of prostaglandin-like material (PG) E, measured by radioimmunoassay, in uterine vein blood within 35 min and PGE levels continued to rise until 3 h after endotoxin and remained elevated until 8–9 ½ h. PGF in uterine vein blood was not elevated until 90 min after endotoxin and then increased more rapidly than PGE during the next 2.5 h: it was still elevated at 8–9 ½ h. The ratio of PGF:PGE in uterine vein blood decreased from 3:1 in 24 h control samples to 1:1 at 1 h after endotoxin, and then increased rapidly exceeding 5:1 at 2 h. In animals given both indomethacin and endotoxin PG levels in uterine vein blood declined. Phenoxybenzamine partially prevented the effect of endotoxin on ovum transport and in animals so treated PGE levels in uterine vein blood increased similarly to those in animals receiving endotoxin alone, but PGF values, while elevated, were suppressed compared to those in endotoxin animals and the PGF:PGE ratio never exceeded 2:1. It is concluded that endotoxin induces accelerated ovum transport by causing an initial relaxation of the oviductal isthmic musculature due to PGE dominance followed by stimulation of oviductal circular musculature due to PGF dominance.

Effects of sympathetic denervation of the rabbit oviduct on normal ovum transport and on transport modified by estrogen and progesterone.

Oviducts were depleted of endogenous sympathetic neurotransmitter by either surgical denervation, or intraluminal infusion of 6-OH-dopamine or systemic administration of reserpine. Functional denervation was confirmed by histochemical examination of the oviducts. These procedures failed to disrupt normal transport rates of ova as indicated by oviductal ovum recovery rates at 48 and 72 h following HCG injection. However, estrogen-induced ‘tube-locking’ of ova and progesterone-induced acceleration of ovum transport were partially antagonized by depletion of neurotransmitter from the intrinsic adrenergic nerves of the oviduct. These data suggest that the effects of sex steroids on ovum transport are partially mediated through adrenergic processes.

Effects of Gonadotropins on Follicular Development, Ovulation, and Atresia in the Mature Guinea Pig

The induction of follicular growth, ovulation, and atresia by heterologous gonadotropic preparations was studied late in the reproductive cycle of the adult female guinea pig. Human chorionic gonadotropin (HCG) administration (10 IU) 12 days following the first signs of opening of the vaginal membrane was found to stimulate ovulation within 24 h in all animals studied, as evidenced by recovery of ova from their oviducts as well as the presence of postovulatory follicles in their ovaries. Histologically, ovaries of animals receiving HCG exhibited atretic changes in most of the follicles smaller than 999 micrometer in diameter. Pregnant mares serum gonadotropin (PMSG, 10 IU) administered on days 9 and 10 of the cycle was not sufficient to stimulate ovulation in this species although histological changes in the follicular complement were observed. Administration of PMSG prior to the HCG appeared to have an inhibitory effect on ovulation induction. Follicles luteinizing with entrapped ova were seen in all groups receiving exogenous gonadotropin, although they were most prevalent in the animals receiving the maximum total gonadotropin doses (i.e. PMSG + HCG).

The Autonomic Nervous System and its Relationship to Tubal Ovum Transport – a Reappraisal

The role of the autonomic nervous system in controlling ovum transport remains obscure. Although not studied extensively in the oviduct, the para-sympathetic nervous system does not appear to significantly influence ovum transport. The sympathetic nervous system of the oviduct and its pharmacology have been studied more thoroughly. Despite this, little information is available concerning cellular mechanisims of adrenergically altered motility or transport. In spite of much speculation, the weight of evidence suggests that, at least in the rabbit, the sympathetic nervous system plays a minor role in the control of ovum transport.

Use of radioactive microspheres for studies of tubal ovum transport

Experiments were designed to ascertain the fidelity with which radioactive plastic ovum models imitated the time-course of transport of natural ova through the rabbit oviduct. After location of the radioactive microspheres within the intact oviducts, the genital tracts were removed and cleared in benzyl benzoate. Natural ova and ovum surrogates were then visualized in situ. The radioactive microspheres were reasonably good models of transport of natural ova and their sojourn in the oviduct was shortened by progesterone and prolonged by estrogen. Thus they should be useful tools for future studies of own transport under various conditions.

Rate of transport of radioactive ovum models through the oviducts of individual rabbits

The transport of radioactive ovum models of 100, 200, 400, 800, and 1,000 mu diameter through the oviducts was measured. Four surrogates of a given size were transferred into each oviduct 6 hours after injection of human chorionic gonadotropin (HCG). The surrogates were located in the oviducts 24, 48, 60, 66, and 72 hours after HCG injection with a collimated end-window Geiger-Mueller tube. Thus the time-course of the transport of each surrogate, from ampulla to uterus in the same animal, was plotted. The time-course of surrogate transport was directly related to surrogate size. Our data suggest that normal tubal patency and ovum transport function can be tested by introducing radioactive ovum surrogates of appropriate size into the oviducts and monitoring their time of arrival at the uterus.

Effect of inhibitors of prostaglandin synthesis and metabolism on ovum transport in the rabbit.

Several drugs known to affect prostaglandin synthesis, release, or metabolism have been tested for their effects on ovum transport in the rabbit after systemic or local administration. Acceleration of transport was obtained with several drugs; among the most effective were benzydamine, a blocker of thromboxane production, and L11204, an inhibitor of prostaglandin metabolism.

Contraceptive properties of endotoxin in rabbits.

Endotoxin derived from Salmonella enteritidis-Boivin at a dose of 20 micrograms/kg intravenously interfered with follicular rupture normally induced by human chorionic gonadotropin (hCG) in rabbits. This action was greatest when the endotoxin was given 5 to 6 hours after the administration of hCG. The failure of follicular rupture resulted in entrapment of ova. Endotoxin (5 micrograms/kg) given intravenously to rabbits on day 4 of pregnancy resulted in failure of implantation. Indomethacin (2 micrograms/kg) given intramuscularly concomitantly was unable to reverse this action. Endotoxin (5 micrograms/kg) given intravenously to rabbits on day 8 of pregnancy had an immediate lethal action on embryonic development, and this effect was inhibited by concomitant indomethacin treatment. Nevertheless, most fetuses died after the indomethacin treatment. Whether this was due to a direct toxic action of indomethacin or to a secondary action of endotoxin not blocked by indomethacin is not clear. Endotoxin did not exert its antifertility actions through a luteolytic mechanism.

Medicated intratubal silastic spheres do not prevent pregnancy in rabbits.

Abstract Plastic or silastic spheres 1.2 – 1.3 mm in diameter were placed in the ampullae of oviducts of rabbits. Spheres remained at the ampullary-isthmic junction but failed to prevent pregnancy after artificial insemination.