Growth and Regression of the Corpora Lutea Formed in Guinea-Pigs in Response to Treatment With Exogenous Gonadotrophin

Abstract

The growth and functional activity of luteal bodies formed in the ovaries of guinea-pigs given exogenous gonadotrophin was examined. Folliclestimulating hormone, luteinizing hormone, both hormones together, and both hormones supplemented with prolactin, were given on day 13. Vaginal oestrus occurred 8-12 days later, irrespective of the kind of hormone given. The sizes of luteal bodies induced in intact and hysterectomized guinea-pigs were compared with those of similarly aged naturally formed corpora lutea 8 and 11 days after ovulation. The artificially induced bodies were smaller than normal corpora lutea, but grew to match their size after hysterectomy.

The Hormonal Induction of Ovulation or of Luteinization in the Intact or Hypophysectomized Guinea-Pig

“…The lack of ovulation early in the cycle cannot be attributed to inadequate treat¬ ment with hormone. It seems highly probable that follicles are resistant to luteiniza¬ tion during the first half of the oestrous cycle: few large follicles are present in the ovaries during this stage of the cycle (Myers, Young & Dempsey, 1936;Dempsey, 1937;Hermreck & Greenwald, 1964;Labhsetwar & Diamond, 1970), and follicular development to maturity seems to require a 10-day period (Dempsey, 1937;Bland & Donovan, 1968;Donovan & Lockhart, 1972). Treatment with FSH on days 8-13 of the cycle induced follicular luteinization, thus confirming the results of others (Aron et al 1958;Reed & Hounslow, 1971).…”

“…The occurrence of ovulation and normal follicular luteinization when both LH and FSH are given, at half the quantities which were ineffective when given singly, to hypophysectomized guinea-pigs 4-5 h after hypophysectomy supports this supposition. The restoration of the luteinizing property of LH, by injection of FSH, is unlikely to be due to a reversal of the process of follicular atresia by the latter hormone, as atresia is generally considered to be a unidirectional process, nor could it be due to the rapid maturation of a new crop of follicles as follicular growth is slow in this species (Dempsey, 1937;Bland & Donovan, 1968;Donovan & Lockhart, 1972) and is difficult to influence by hormone treatment (Perry & Rowlands, 1963;A. N. Lockhart, unpublished results).…”

“…Similar results were obtained in hypophysectomized animals and, further, threshold amounts of either FSH or LH stimulated follicular growth when injected into the ovaries of hypophysectomized animals, whereas luteinization followed comparable treatment with larger quantities of either hormone (Aron, Aron, Marescaux & Petrovic, 1958). Follicle-stimulating hormone has been shown to induce follicular luteinization in the intact rat (Aron, Roos, & Asch, 1969;Harrington & Elton, 1969), rabbit (Greep et al 1942) and guinea-pig (Marescaux, Aron & Aron, 1957;Reed & Hounslow, 1971;Donovan & Lockhart, 1972).…”

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

“…The incidence of entrapped ova in luteinizing follicles was greatest in the group receiving the combined PMSG-HCG treatment and may represent an excessive stimulation of the follicular apparatus. This is apparently a common response of the guinea pig ovary to exogenous gonadotropin (Hamburger and Pedersen-Bjergaard, 1946;Perry and Rowlands, 1963;Deane sly, 1966;Das and Benson, 1970;Donovan and Lockhart, 1972), and suggests that further decreases in the total gonado tropin dosage may be warranted.…”

Stimulation of the hypothalamus and ovulation in the guinea‐pig

“…Since Donovan & Lockhart (1972) found enhanced luteal development in hysterectomized guinea-pigs induced to ovulate with LH or follicle stimulating hormone, it was possible that the uterus inhibited the formation as well as the development of the new corpora lutea. However, full ovulatory responses did not occur in hysterectomized guinea-pigs responding to medial basal hypothalamic stimulation.…”