Effects of a Luteinizing Hormone-Releasing Hormone Antagonist in Late-Juvenile Female Rats: Blockade of Follicle Growth and Delay of First Ovulation Following Suppression of Gonadotropin Concentrations

BIOLOGY OF 43, 607-613 REPRODUCTION Effects Female (1990) of a Luteinizing Hormone-Releasing Hormone Antagonist in Late-Juvenile Rats: Blockade of Follicle Growth and Delay of First Ovulation Following Suppression of Gonadotropin Concentrations H. M. A. MEIJS-ROELOFS,t Department W. P. KRAMER. of Anatomy, Medical A. VAN Facu4y, CAPPELLEN, Erasmus and E. C. M. VAN Rotterdam, Univeiizy, The LEEUWEN Netherlands ABSTRACT and on influence follicle 28, 31, 34, and 37. (p 2, 3, and 4 fofficles I follicles Class on lower 3 days after a further decrease 3 days LHRH-A delay sexual of LHRH-A lowered ovaries. in 3 of (0/6 rats) gonadotropin 28 The dose the 2.5 (0/8 pg 3, and LHRII-A subsequent if given after the Days first, and that study, onist against LHRH juvenile period was if the treatment chronic (LHRH-A), effective period of this LHRH-A effective as well, and on the day significantly crease in LH Secretion lation [2, 3, 4, 5], decreased to rats be to such without the surge. gonadotropin approaching possible crease in basal LH secretion maturation would be delayed preovulatory to an of LH and FSH, and inhibit To achieve on in- first this follicle this, dynamics ad single (Org. of first was were Class of Class total absence 3 and proestrus not of 4 follicles blocked blocked female with rats may AND METHODS of a Wistar days substrain of age of 22-25#{176}C with Standard dry pellets From 28 days and (R-Amsterkept in a con- a light period and tap water of age, from were groups of rats or repeated subcutaneous injections 30276, Ac-D-pClPhe-DpClPhe-D-Trp-Ser-Tyr- of an 37 days of age. Doses body wt were used. since in a previous in- of 100, This experimental study on infantile 250, or 500 p.g/100 scheme was rats, injection dose of 500 p.g LHRH-A/100 g body wt maximally pressed gonadotropin secretion for 3-5 days [6]. 1, effects In Experiment rats with con- of LHRH-A g chosen of the sup- on the timing of vag- inal opening and first estrus were studied (Table 1). Rats were checked daily for body wt and vaginal opening from the day of first vaginal smears were injection. From the day of vaginal opening, were taken daily until the rats were killed. Occurrence of firstovulation was established by a fully cornified estrous smear and by the presence of CL in the ova- Accepted May Received 24, 1990. January ‘Correspondence: P.O. and 4.7 Days LHR}l-A number to late-juvenile at 22 libitum. ries, observed EUR. day on of (antral) Class ovulation rats weaned received LHRH-A a more to female of treatment on serum were available and ovu- extent that sexual direct inhibition of potent LHRH-A, Org. 30276, was administered during the late-juvenile period. The effects this LHRH-A on the timing of first ovulation, centrations studied. the pg; pg did by if given higher injection; 34, D-Arg-Leu-Arg-Pro-D-Ala-NH2 CH3 COOH; Organon, Oss, The Netherlands) or solvent. Org. 30276 was dissolved in saline (0.9% NaCl) immediately before use. Injections were always administered between 1100 and 1130 h at 28, 31, 34, to those of the gradual importance in female it should compared female trolled temperature 0500-1900 h daily. of firstproes- thus the delay had of 500 and growth. dam) lateonly days injection, of LHRH-A Immature be attributed to acute inhibition of the preovulatory gonadotropin surge by LHRH-A. However, serum LH concentrations found in these chronically LHRH-A-treated, nonrats were 10 31, of follicle growth at an early antral stage. The dose surge is only a fraction of that causing chronically arrest gonadotropin the day of firstproestrus trus only was in controls [1]. In view of the apparent h on adminconcen- retarded numbers a significantly LHRH-A 28, was 11.5 injections LHRH-A administration of an antag- Org. 30093, during the in delaying first ovulation [1].Administration delayed 28; 5 and Days decreased third given by MATERIALS administration included ovulation second the INTRODUCTiON In a previous on wt, 34; and were gonadotropin serum given third at 0900 rats causing of follicle Day the after and showed on after wi, and counts administered concluded 31, second, days 12/12) levels, ovulatory 28, wt on g body 30276) Org. (LHRH-A, ovulation g body follicle Six of LHRH-A blockade on 3 days injection. first LHRH-A/100 g body 4 fofficles It was in gofladotropin of the first pg Ovarian in all (8/8 and LHRH-A/100 pg LHRH-A/l00 injection and rats). by a decrease acute inhibition days hormone opening of 500 3 days 2, pg 100 controls. third low-dose given of 31; by 6.7 of 500 in Class after hormone-releasing of vaginal administration and injection and timing in saline-treated or saline levels on concentrations FSH A single, 11 rats maturation needed for After than 5 follicles in the studied. Days LH and Serum 0.01) and ovulation 1 pg given luteinizing against effects ovulation. 3, 4, and reappeared first < The were growth were significantly rats. of first timing if injections days female Box 1738, later confirmed 3, 1990. Dr. 3000 H.MA. Meijs-Roelofs, DR Rotterdam, The Dept. of Anatomy, Medical A/100 Faculty, bled Netherlands. 607 g body at 1100 on the same wt h and or saline 1500 and day by laparoscopy histologically. Rats receiving on h on Days the 28, day 31, 500 and of estrus always p.g LHRH34 were for esti- to late-juvenile trations not of an antagonist injections Subcutaneous istered 608 MEIJS-ROELOFS TABLE 1. Experimental blood sampling, autopsy, Dose of LHRH-A or saline (sg/100 g) scheme of injections with LHRH-A (Org. and ovariectomy for histological follicle Injection Day Blood sample Day 34 37 x x x x x x Saline x x 500 x x Saline x x x first 500 x x x firstE Saline x x x x x x x x x x x x No. of rats 1’ 500 Experiment Saline 100 x x Saline x x 500 x x 9 oocyte that mulus cells - 9 ameters 8 nected with an Olivetti M24 Microcomputer the third diameter by the mean of the two 8 20 - 12 - 11 37 37 x x 37 37 4 5 31 31 12 11 x x 34 500 x x 34 11 12 Saline x x x 500 x x x 37 37 10 10 Saline x x x x x x at first estrus; ovaries on the day of blood measurement = estrus. **ln this group, the 6 -“ 40 12 fixed for histological counting of CL. sampling; ovaries fixed for histological of follicles. ovaries fixed on the day of first of serum concentrations of LH as tracer Rats were smear day the next day. These of proestrus Histology by the presence and rats were imminent vaginal of a fully cornified bled at 1600 h on the and killed at 1100 h on the day of estrus. Follicle Counts Se (...truncated)