Effect of Administration of Anti-Serum to Luteinizing Hormone-Releasing Hormone on Gonadal Function During the Estrous Cycle in the Hamster

Abstract

One-half ml of sheep-anti-LHRH-serum (No. 772) completely blocked ovulation when administered iv or sc at any stage of the estrous cycle in cycling hamsters. This anti-ovulatory activity lasted 12-13 days. The minimal effective iv dose (MED) of the anti-LHRH serum for completely blocking the preovulatory LH surge and ovulation when administered at 1200 h on proestrus was 0.2 ml. Injection of LHRH on the afternoon of P (proestrus) induced ovulation in the antiserum-treated hamsters when the antiserum was injected on P, but not when injected on D1 (diestrus 1) or D2 (diestrus 2). This suggests that the anti-LHRH serum acts differently in blocking ovulation during D and P, by suppressing follicular development and inhibiting preovulatory surge of gonadotropins, respectively. Serum estradiol levels, measured by radioimmunoassay, were significantly reduced but not completely suppressed after injection of 0.5 ml of anti-LHRH-serum. Histological examinations of the ovaries revealed that an arrest of follicular maturation resulted 3 days after antiserum injection. 17-beta-Estradiol administered 22 h before the presumptive preovulatory LH surge improved significantly (P less than 0.05) the LH response to LHRH in the antiserum-blocked hamsters. This suggests a direct modulation of pituitary LH responsiveness by estradiol in the absence of endogenous LHRH activity. When the integrated levels of serum LH following an injection of a minimum effective dose of exogenous LHRH to induce full ovulation in anti-serum-blocked hamsters were compared with those during the physiological preovulatory LH surge, it was found that only 11% of the amount of LH released on the afternoon of proestrus was sufficient for inducing full ovulation.

Effect of oestrogen and an LH-RH agonist on the release of gonadotrophins in ovariectomized ewes deprived of LH-RH

“…The presence of small amounts of biologically active LH-RH may also explain why some FSH is detectable in the plasma of LH-RH immunized ewes. Nevertheless, in these ewes the action of LH-RH is effectively blocked and as the source of the ovarian steroid hormones is also absent they provide an in-vivo system with which to study the ability of oestrogen and LH-RH agonists to stimulate the secretion of LH (Fraser & Sandow, 1977;Clarke et al, 1978;Jeffcoate et al, 1978 (Koch et al, 1973), hamster (de la Cruz et al, 1976) and fowl (Fraser & Sharp, 1978), but are in marked contrast to the lack of effect in the rhesus monkey, in which administration of antibodies both before and after oestrogen injection failed to abolish the LH surge (McCormack et al, 1977).…”

“…Injection of LH-RH antiserum to rats and hamsters at 12:00 h on the day of pro-oestrus prevents the peovulatory LH surge (Koch, Chobsieng, Zor, Fridkin & Lindner, 1973;de la Cruz, Arimura, de la Cruz & Schally, 1976), and to chickens blocks the progesterone-induced LH surge (Fraser & Sharp, 1978). In marked contrast, LH-RH antiserum was without effect on the oestrogen-induced LH surge in the rhesus monkey (McCormack, Plant, Hess & Knobil, 1977).…”

Differential effects of LH-RH immunoneutralization on LH and FSH secretion in the ewe

“…Passive immunoneutralization of luteinizing hormone-releasing hormone (LH-RH) prevents the preovulatory surge of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the rat (Koch, Chobsieng, Zor, Fridkin & Lindner, 1973;Arimura, Debeljuk & Schally, 1974;Kerdelhue, Catin, Kordon & Jutisz, 1976; Kawakami & Higuchi, 1979), hamster (de la Cruz, Arimura, de la Cruz & Schally, 1976) and ewe (Narayana & Dobson, 1979;Fraser & McNeilly, 1982). However, little is known about the changes associated with neutralization of LH-RH on tonic gonadotrophin secretion in the intact female.…”

Recent Developments in the Study of Hypothalamic Hormones with Special Reference to LH-RH and Somatostatin

“…419 crossreacts with In plasma or serum, there are various substances which interfere with RIA by suppressing tracer-antibody binding in a non-competitive manner. Unless these interfering substances are removed beforehand, the estimated value of hormone concentration by RIA may be invalid (12). The extent of such nonspecific interference may differ from one antiserum to another.…”

“…These interfering substances could be removed by extracting plasma LH-RH by acetone or ethanol, but the elimination was incomplete. It was found that extraction of plasma LH-RH with Florisil could remove most of these interfering substances (12). Recovery of 5 to 100 pg LH-RH, added to 5 ml plasma after Florisil extraction, averaged 75%.…”