Follicular development, oocyte viability and recovery in relation to follicular steroids, prolactin and glycosaminoglycans throughout the estrous period in superovulated heifers with a normal LH surge, no detectable LH surge, and progestin inhibition of LH surge.
Estrous cycles of heifers (n = 137) were synchronized with prostaglandin (PGF2 alpha) and follicular development stimulated with follicle stimulating hormone. Twenty-eight animals were administered Norgestomet implants 12 hr prior to the initial PGF2 alpha injection to suppress the LH surge that initiates ovulation. Animals were ovariectomized every 12 hr after the initial PGF2 alpha (7-9/time, 12-108 hr and at 192 and 240 hr post PGF2 alpha) and divided into three treatment groups to consist of: 1) animals exhibiting a normal luteinizing hormone (LH) surge (n = 86), 2) animals in which no LH surge was detected (n = 23), and 3) suppression of the LH surge via Norgestomet implants (72-108 hr, n = 28). Follicular diameter was measured and follicular fluid was collected for analysis of prolactin, estradiol, progesterone and glycosaminoglycan concentrations. Progesterone concentrations were increased in animals exhibiting an LH surge as compared to animals in which no LH surge was detected; primarily in large follicles (> 8 mm diameter) after the LH surge. Animals not exhibiting an LH surge also had increased follicular progesterone concentrations compared to Norgestomet-implanted animals (242.3 +/- 36.3 vs 86.7 +/- 6.4 ng/ml, respectively, P < .01), indicating some LH stimulation. Follicular estradiol in animals exhibiting an LH surge increased up to the time of LH surge detection and then declined whereas animals with no LH surge detected had follicular estradiol concentrations that declined after the PGF2 alpha injection. No differences were noted between those that did not exhibit an LH surge or in which the LH surge was suppressed with Norgestomet in relation to follicular estradiol concentrations. Follicular estradiol concentrations increased with follicular size in all treatment groups (P < .01). Follicular concentrations of prolactin were increased in small follicles (P < .05; < or = 4 mm diameter) and follicular prolactin increased from 12 to 36 hr post PGF2 alpha injection, then declined after the LH surge. Follicular glycosaminoglycan concentrations decreased with increases in follicular size (P < .01) and were higher in animals that did not exhibit an LH surge (P < .01). No differences in follicular glycosaminoglycans were noted between Norgestomet-implanted animals and those not exhibiting an LH surge. In the animals representing days 4 and 6 of the subsequent estrous cycle (192 and 240 hr post PGF2 alpha), numbers of small-sized follicles were increased. Follicular progesterone and estradiol concentrations were related to atretic large follicles unovulated from the prior estrus and a new wave of growth in small and medium follicles.(ABSTRACT TRUNCATED AT 400 WORDS)
Wise
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U.S. Department of Agriculture, Roman L. Hruska U.S. Meat Animal Research Center, Nebraska 68933-0166.
Maurer
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D000818:Animals; D002417:Cattle / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000502:physiology*; D005260:Female; D015571:Follicular Fluid / Q000737:chemistry; D006025:Glycosaminoglycans / Q000737:chemistry* / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology*; D006080:Ovarian Follicle / Q000502:physiology*; D011282:Pregnenediones / Q000494:pharmacology; D011374:Progesterone / Q000037:antagonists & inhibitors / Q000097:blood / Q000502:physiology*; D011388:Prolactin / Q000097:blood / Q000737:chemistry*; D013480:Superovulation / Q000502:physiology*
D006025:Glycosaminoglycans; D011282:Pregnenediones; C100284:norgestomet; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone