Luteinizing hormone increases the number of ova shed in the cyclic hamster and guinea-pig

Abstract

Osmotic minipumps containing 400 micrograms ovine LH installed subcutaneously on day 1 (oestrus) of the cycle in the hamster induced superovulation of 30.0 +/- 2.1 ova (n = 5) at the next expected oestrus. Controls ovulated 12.0 +/- 0.8 ova (n = 6). Bovine LH, human LH, porcine LH, human chorionic gonadotrophin and pregnant mare serum gonadotrophin were effective in approximately doubling the number of ova spontaneously shed in the hamster. Ovine FSH (200 micrograms/pump) was most effective in increasing the number of ova spontaneously shed (55 +/- 6, n = 5) in the hamster. Infusion of ovine LH on days 1-4 prevented the reduction of the number of antral follicles that occurs normally between days 3 and 4 of the 4-day cycle. Since this reduction in follicular numbers in control cyclic hamsters is due to atresia, the exogenous LH might prevent atresia of the developing follicles. In the hamster, exogenous ovine LH significantly increased the serum concentrations of androstenedione, oestradiol and LH but not of FSH. Hamsters were hypophysectomized on the day of oestrus, given immediate LH (400 micrograms) or FSH (200 micrograms) replacement therapy and autopsied on day 4. Ovarian histology revealed that immediate LH treatment after hypophysectomy sustained development of histologically normal preovulatory follicles but had no effect on the number of smaller sizes of follicles. Immediate FSH treatment after hypophysectomy increased only the number of smaller sized follicles. Since LH did not increase the smaller sized follicles, no 'FSH-like' effect on follicular development was observed. In the hamster, the ability of various preparations of LH to induce superovulation did not correlate with their ability to displace 125I-labelled ovine FSH from its ovarian binding sites. The superovulatory action of LH required the presence of the pituitary gland, indicating that LH might synergize with FSH and/or prolactin (or hamster LH) for spontaneous superovulation and it appears that exogenous LH might induce superovulation by prevention of atresia. Infusion of LH into the guinea-pig beginning on day 12 of the cycle (day 1 is the day of ovulation) doubled the ovulation rate whereas in the cyclic rat and mouse LH treatment throughout the cycle was ineffective in increasing the number of ova shed.

Histamine and increased ovarian blood flow mediate LH-induced superovulation in the cyclic hamster

“…Osmotic minipumps (no. 2001, Alza Corp., Palo Alto, CA, U.S.A.) containing 400 µg ovine LH (S-24) in 0-01 mphosphate-buffered normal saline (PBS) with 0-1% bovine serum albumin (BSA), pH70, or PBS-BSA alone were inserted s.c. on Day 1 of the cycle at 09:00-10:00 h as previously described in detail by Garza et al (1984). Each hamster received a single pump.…”

“…The study of Garza, Shaban & Terranova (1984) has shown that constant infusion of moderate amounts of LH during the cycle induced superovulation in the cyclic hamster. The superovulatory action of LH required the presence of the pituitary, suggesting that LH might synergize with FSH for spontaneous superovulation.…”

Elevated peripheral concentrations of LH block ovulation and increase thecal and serum progesterone in the hamster

“…To insert the osmotic minipumps on Day 1 at 09:00-10:00 h, hamsters were anaesthetized lightly with ether and a 1-cm incision was made through the skin on the back between the scapulae as described in detail by Garza et al (1984) Gibco,Grand Island, NY, U.S.A.) supplemented with 01% bovine serum albumin. Three or 4 follicles/animal were stimulated in vitro in 1 ml incubation medium with 100 ng LH (NIH), or 0-1 or 1-0 µ -androstenedione.…”

“…Elevation of circulating concentrations of LH increases the number of ova shed by 2-3 times in the cyclic hamster (Garza, Shaban & Terranova, 1984); however, a few animals treated with human LH or hCG (in which numerous preovulatory follicles were observed) exhibited a blockade of ovulation. This blockade of ovulation was believed to be due to extremely elevated LH or hCG values which either altered the sensitivity of follicular gonadotrophin receptors to prevent ovulation or increased the serum concentration of progesterone resulting in a hypothalamic block to ovulation (Greenwald, 1978(Greenwald, , 1982.…”

Effect of Pregnant Mare's Serum Gonadotropin on Increased Ovulation in Guinea Pigs with Synchronized Estrous Cycle

“…In cyclic guinea pigs, both treatment of an antiserum to LH and infusion of ovine LH using an osmotic minipump induced superovulation [5,10] . However, these successful methods to cause increased ovulation can be used by only some specified investigaters.…”