FSH influences follicle viability, oestradiol biosynthesis and ovulation rate in Romney ewes

Abstract

Summary. Injection of steroid-free bovine follicular fluid (bFF; 2 \m=x\5 ml s.c. 12h apart) into anoestrous ewes lowered plasma FSH concentrations by 70% and after 24 h had significantly (P < 0\m=.\01) reduced the number of non-atretic follicles (\ m=ge\ 1 mm diam.) without influencing the total number of follicles (\ m=ge\ 1 mm diam.) compared to untreated controls. Hourly injections of FSH (10 \g=m\g i.v. NIH-FSH-S12) for 24 h did not influence the number of non-atretic follicles but did negate the inhibitory effects of bFF on follicular viability. Hourly injections of FSH (50 \ g=m\ gi.v., NIH-FSH-S12) + bFF treatment for 24 h significantly increased the total number of non-atretic follicles, and particularly the number of medium to large non-atretic follicles (\ m=ge\ 3 mm diam.) compared to the untreated controls (both P < 0\m=.\01). The 10\g=m\g FSH regimen (without bFF) significantly increased aromatase activity in granulosa cells from large ( \ m=ge\ 5 mm diam.; P < 0\m=.\01) but not medium (3\ p=n-\ 4\ m=. \ 5 mm diam.) or small (1\ p=n-\ 2\ m=. \ 5 mm diam.) follicles compared to controls. The 10 \g=m\g FSH + bFF regimen had no effect on granulosa-cell aromatase activity compared to the controls. However, the 50 \g=m\g FSH plus bFF regimen increased the aromatase activity of granulosa cells from large, medium and small non-atretic follicles 2\m=.\6-,8\m=.\3-and \m=ge\11-fold respectively compared to that in the control cells. Ewes (N = 11) that ovulated 2 follicles had significantly higher plasma FSH concentrations from 48 to 24 h and 24 to 0 h before the onset of a cloprostenol-induced follicular phase (both P < 0\m=.\01) than in the ewes (N = 12) that subsequently ovulated one follicle. Hourly FSH treatment (1\m=.\6 \ g =m\ g i.v., NIAMDD-FSH-S15) for 24 h but not for any 6 h intervals between 48 and 24 h or 24 and 0 h before a cloprostenol-induced luteolysis also resulted in significant increases (P < 0\m=.\05) in the number of ewes with 2 ovulations.We conclude that (1) the number of non-atretic antral follicles in sheep ovaries is influenced by plasma FSH concentrations; (2) the level of follicular oestradiol biosynthesis can be enhanced by FSH treatment; and (3) sustained elevations of plasma FSH concentrations for 24 h but not 6 h within 48 h of the onset of luteolysis significantly enhances the ovulation rate in Romney ewes.

Follicle development, endocrine profiles and ovulation rate in adult Merino ewes: effects of early nutrition (pre- and post-natal) and supplementation with lupin grain

“…A small slit was made in the follicle wall to allow the antral fluid to escape into a Petri dish, from where it was aspirated through a finely drawn-out Pasteur pipette, taking care not to remove clumps or sheets of granulosa cells. A known volume of the follicular fluid was added to 100 ml PBS and frozen at K20 8C for subsequent measurement of E 2 concentrations, the most reliable indicator of the health status of antral follicles over a wide range of sizes (McNatty et al 1985). The granulosa cells were recovered and counted by using haemocytometer.…”

“…red, pink or white) was recorded. For the purpose of this study, a healthy follicle was defined as one with i) visible thecal blood capillaries, ii) follicular fluid devoid of debris, iii) a pink-to red-coloured theca interna, iv) a normal-looking and intact oocyte-cumulus cell complex and v) more than 25% of the maximum number of granulosa cells for a given follicle size (McNatty et al 1985). Conversely, an atretic follicle was one to which any of these criteria did not apply.…”

Use of bovine follicular fluid to increase ovulation rate or prevent ovulation in sheep

“…In the present study, the increased ovulation rate followed treatment with relatively small amounts of follicular fluid for only 3 days after the start of luteolysis. Administration of FSH or substances with FSH-like activity will increase ovulation rate in sheep (Wright et al, 1981;Boland et al, 1983;Kelly et al, 1983;McNatty et al, 1985). Perhaps the elevated plasma concentrations of FSH and LH occurring on cessation of treatment allowed a greater than normal number of follicles to attain ovulatory maturity in synchrony in some ewes, hence the increased frequency of multiple ovulations.…”

Active Immunization Against 5.ALPHA.-androstane-3.ALPHA.,17.BETA.-diol Increases Ovulation Rate in Merino Ewes.

“…In the present study, a significant correlation was found between mean plasma concentrations of FSH during the mid-luteal phase and the number of CL formed in the following cycle. Mean concentrations of FSH in ewes with 2 and 3 ovulations were well in excess of that required to increase the ovulation rate from 1 to 2 [17]. Therefore, increased concentrations of FSH, in response to 3α-diol-immunization are likely to be at least partially responsible for the increased ovulation rate in these ewes.…”

“…In this experiment, however, concentrations of FSH were significantly increased by 3α-diol immunization during the mid-luteal phase, a result similar to that reported in A4-immunized ewes by McNatty et al [15], who concluded that the increased FSH concentrations were at least partially responsible for the increased ovulation rate in A4-immunized ewes. It has been well documented that treatments with exogenous FSH [17][18][19] or treatments that i n c r e a s e e n d o g e n o u s F S H l e v e l s s u c h a s immunization against inhibin [21,22] or E2 [1,22], all increase ovulation rates in ewes. In the present study, a significant correlation was found between mean plasma concentrations of FSH during the mid-luteal phase and the number of CL formed in the following cycle.…”