Effects of gonadotrophins on motility of human ovary

The role of follicular smooth muscle cells in hamster ovulation

The role of contractile cells in mammalian ovulation is uncertain. In this study, we examined the morphology and distribution of cells within the theca externa of hamster follicles at various times during ovulation. Cells with all the ultrastructural features of smooth muscle (SMC) were found only in the basal hemisphere of the follicle. In contrast, the theca externa in the top half of the follicle was composed of fibroblasts. We next examined living hamster follicles during in vitro ovulation for morphological evidence of follicular contraction. The following changes in follicle shape were observed: (1) The base of the follicle moved apically; (2) follicles, which were initially spherical, became taller and thinner; and (3) after rupture, the apical follicle wall collapsed onto the surface of the ovary. To analyze the cause of these changes, sections of fixed follicles were examined by light and electron microscopy. During the final minutes before rupture, a V-shaped constriction formed in the base of the follicle. This constriction continued to narrow and by the time of rupture, it obliterated the basal part of the antrum. We concluded that the apical movement of the base of the follicle seen in living ovaries corresponds to the formation of the basal constriction seen in fixed sections. To determine if follicular SMC were involved in formation of the constriction, the ultrastructure of SMC was examined before, during, and after the constriction formed. The morphology of the SMC changed from the characteristic of relaxed or stretched SMC to that of contracted SMC when the constriction began to form. No other type of cell in the follicle wall showed these changes in morphology. We conclude that the formation of this constriction, and possibly the increase in height of preovulatory follicles and the collapse of the follicle wall after rupture, are due to contraction of SMC in the theca externa in the basal hemisphere of the follicle. This is the first morphological demonstration that follicular SMC contract prior to rupture of the follicle. The significance of these observations in mammalian ovulation is discussed.

[Measurements of spontaneous pressure changes in the arterial vessels and in the tissue of bovine ovaries perfused in vitro (author's transl)]

12 bovine ovaries were perfused in a closed circuit system using a semisynthetic hemoglobinfree perfusate. The pressure in the ovarian tissue and the arterial pressure were recorded simultaneously. Arterial and tissue pressure changes were noticed in bovine ovaries, as have been described in other species. It could be shown that pressure in the vascular system and the arterial pressure may vary independently. It appears as if spontaneous pressure changes in the in vitro perfused ovary are more pronounced in frequency and amplitude during the phase of follicle maturation.

[Studies on the dependence of intrafollicular pressure on the pressure in the intraovarian-vascular-system and tissue, carried out in vitro on human ovaries (author's transl)]

The intrafollicular, intraovarian and intraarterial hydrostatic pressures were measured in vitro on human ovaries in the vollicular ripening phase. It has been established that in the vascular system as well as in the intraovarian tissues pressure variations occur spontaneously. Thus for example under, the influence of epinephrine, norepinephrine, prostaglandine F2 alpha and oxytocine, the tonicity of the vascular system increases and does so the number of spontaneous contractions rather noticeably, particularly under the influence of prostaglandine F2alpha, and under the various catecholamines an increase of frequency and amplitude has been observed. Any increase of pressure in the intraovarian vascular system and tissues will effect all the follicles not yet in the preovulatorian phase, in which they cause a similar pressure increase. However, follicles imminently preovulatorian have not shown such pressure increase because the increase of the "liquor folliculi" runs parallel to the increasing elasticity of the follicle walls. The findings are discussed in this article with a particular view of the biophysical aspects of ovulation.

Localization of actin and myosin in the rat oocyte and follicular wall by immunofluorescence

The distribution of actin and myosin in the rat ovary at different stages of postnatal development was studied by examination of cryostat sections treated with antibodies to chicken smooth muscle (gizzard) myosin or to chicken (pectoral muscle) actin and subsequently with fluoresceinated goat anti-rabbit gamma-globulins. Staining with either antiserum revealed several layers of intensely fluorescent elongated cells within the theca externa, forming a coherent band around the larger Graafian follicles. In smaller follicles, this band of fluorescent cells was incomplete, and ovaries of immature (6-day-old) rats were devoid of strongly fluorescent cells. Corpora lutea contained only scattered fluorescent cells at their circumference. Sections of mature ovaries incubated with antibodies raised against striated (pigeon pectoral) muscle myosin generated no significant fluorescence. Large oocytes stained with either anti-actin or anti-smooth muscle myosin showed a thin fluorescent band just beneath the zona pellucida, suggesting that actin and myosin are associated with the oolemma. The distribution of the two antigens in serial sections of follicles coincided, suggesting that the same cells contained both actin and myosin. It is suggested that follicular growth and maturation is attended by the development of a smooth muscle layer in the theca and that contraction of this layer in response to catecholamines and/or prostaglandins may play a role in the extrusion of the oocyte. The role of contractile elements in the oocyte remains to be elucidated.

Influence of the estrous cycle on the action of oxytocin on rat ovarian contractility in vivo

This investigation was designed to determine the influence of the estrous cycle on the response of ovarian smooth muscle to oxytocin. Muscular activity in vivo was studied by recording intraovarian pressure. Intra-aortic injections of oxytocin were given to the rats at all stages of the estrous cycle. The effect of oxytocin was evaluated by the number of responding ovaries and the magnitude of the responses. According to these parameters, a greater response was observed during proestrus, compared with the other cycle stages. The significance of these results id discussed.

Spontaneous and prostaglandin- or oxytocin-induced motility of rat ovaries isolated during different stages of the estrous cycle: effects of norepinephrine

Ovaries isolated from rats in different stages of the sex cycle were explored for spontaneous or drug-induced contractile activity. The number of spontaneously active ovaries as well as the magnitude of the isometrically developed tension and frequency of contractions were greater during the periovulatory interval (late proestrus and estrus) than during early proestrus or metestrus. Furthermore, during estrus or late proestrus the left ovaries exhibited a mechanical activity significantly greater than that of the right ovaries. The oxytocin-triggered motility was clearly more marked immediately prior to ovulation (late proestrus) and greater in left ovaries than in right ovaries. In contrast, the contractions induced by prostaglandin F2alpha were similar during early proestrus and late proestrus. Ovarian contractile reactivity to norepinephrine indicated the presence in the tissue of alpha- and beta-adrenergic receptors. During early proestrus this agent stimulated the motility of left and right ovaries, whereas close to the ovulatory interval (late proestrus) it depressed the contractions of left ovaries. This last influence was blocked by propranolol. The existence of a close relationship between ovarian contractile activity and ovulation is reinforced by the present results in the rat. A tentative participation of oxytocin is also suggested. In addition, the influences of other possible regulatory agents of ovarian contraction, such as catecholamines and prostaglandins, are presented and discussed.

Effectiveness of prostaglandin f 2 alpha in restoration of HMG-HCG induced ovulation in indomethacin-treated rhesus monkeys

Six mature female rhesus monkeys were treated with HMG-HCG in control cycles at doses adjusted to induce ovulation while avoiding superovulation. Occurrence of ovulation was determined by observation of fresh ovulation points at laparotomy 48 to 120 hours following HCG. In subsequent cycles animals were treated with indomethacin (treatment days 4 through 10) together with the established dose of HMG-HCG. In 8 cycles indomethacin 5 mg/kg was given i.m. once daily; in 9 cycles 10 mg/kg i.m. was administered in 2 divided doses. Following this, PGF2alpha (3 mg t.i.d. s.c.) was administered for 3 days together with indomethacin 10 mg/kg and HMG-HCG, beginning on the day prior to HCG. Determinations of progesterone were performed by RIA on treatment days 4, 7, 10, and 11. Eleven of the 13 control cycles were ovulatory. With indomethacin 5 mg/kg/day, 5 of 8 cycles were ovulatory but ovulation was delayed in 2 instances. Of 9 cycles using indomethacin 10 mg/kg/day only 1 was ovulatory. When PGF2alpha was administered in susequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF2alpha may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.