Regulation of messenger ribonucleic acid encoding 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase in the ovine corpus luteum

Three experiments were conducted to determine how steady-state levels of mRNA encoding 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) in the ovine corpus luteum vary 1) between the two steroidogenic luteal cell types, 2) during the estrous cycle, and 3) during prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis. In the first experiment, RNA (10 micrograms) was isolated from purified preparations (n = 4) of large or small steroidogenic luteal cells. Large luteal cells contained 42% more (p < 0.05) message for 3 beta-HSD per microgram RNA than did small luteal cells, while the amount of mRNA for tubulin did not differ between the two types of luteal cells. To determine whether luteal levels of mRNA for 3 beta-HSD differ during the estrous cycle, corpora lutea were collected from cycling ewes (n = 3/day) on Days 3, 6, 9, 12, and 15 postestrus. Levels of mRNA for 3 beta-HSD were similar on Days 3, 6, 9, and 12 but were lower (p < 0.05) on Day 15 postestrus, while levels of mRNA for tubulin were unchanged. In the final experiment, ewes were treated on Day 10 postestrus with two injections of PGF2 alpha (5 mg each) or saline (control) at a 4-h interval. Corpora lutea were collected from ewes (n = 4/treatment) 1 h or 8 h after the second injection of PGF2 alpha or 8 h after the second saline injection.(ABSTRACT TRUNCATED AT 250 WORDS)