Changes in levels of messenger ribonucleic acid for cytochrome P450 side-chain cleavage and 3 beta-hydroxysteroid dehydrogenase during prostaglandin F2 alpha-induced luteolysis in cattle.
Regression of the CL causes a dramatic decrease in plasma progesterone levels. To test the hypothesis that the decrease in progesterone involves the down-regulation of mRNA encoding the steroidogenic enzymes, cytochrome P450 side-chain cleavage (P450scc) and/or 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), levels of plasma progesterone and luteal mRNA for P450scc and 3 beta-HSD were measured and correlated during induced luteolysis. Holstein heifers (n = 25) were injected with 25 mg prostaglandin F2 alpha (PGF2 alpha) on Day 6 or 7 of the estrous cycle (Day 0 = estrus) to induce luteal regression. To determine acute changes in plasma progesterone during luteolysis, jugular blood samples were obtained from 5 heifers hourly for 12 h, beginning immediately before injection of PGF2 alpha, and assayed for progesterone by RIA. A significant decrease in plasma progesterone levels was observed as early as 1 h after the PGF2 alpha injection (3.62 vs. 2.72 ng/ml, p < 0.05). Progesterone levels continued to decline with time through 12 h after administration of PGF2 alpha. The other 20 animals were ovariectomized at 0 (n = 6), 2 (n = 4), 12 (n = 4), or 24 (n = 6) h after PGF2 alpha. Levels of P450scc and 3 beta-HSD mRNA were determined in extracts of total luteal RNA by ribonuclease (RNase) protection assay. By 2 h after PGF2 alpha, 3 beta-HSD mRNA levels had decreased by about 40% as compared with levels at time 0 (p < 0.05), and a further significant decrease occurred between 2 and 12 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Tian
X C
XC
Department and Section of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853.
Berndtson
A K
AK
Fortune
J E
JE
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics*; D000818:Animals; D015152:Blotting, Northern; D002417:Cattle / Q000502:physiology*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics*; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology*; D015237:Dinoprost / Q000494:pharmacology*; D005260:Female; D017403:In Situ Hybridization; D007700:Kinetics; D011374:Progesterone / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism*
D012333:RNA, Messenger; D011374:Progesterone; D015237:Dinoprost; D015096:3-Hydroxysteroid Dehydrogenases; D002786:Cholesterol Side-Chain Cleavage Enzyme