Prostaglandin G/H synthase-2 is expressed in bovine preovulatory follicles after the endogenous surge of luteinizing hormone.
To determine whether prostaglandin G/H synthase-2 (PGHS-2) induction occurs under physiological conditions, heifers were ovariectomized and preovulatory follicles were isolated 0 (n = 4), 18 (n = 4), and 24 h (n = 4) after the onset of estrus. The time of the LH surge was determined in blood samples collected every 4 h pre- and postestrus. Preparations of follicle wall and isolated theca interna and granulosa cells were analyzed for PGHS-2 protein and mRNA by immunoblot and Northern blot, respectively. Immunohistochemistry was used to document the in situ localization of PGHS-2 protein, and follicular fluid concentrations of prostaglandin (PG) E2 and PGF2alpha were determined to monitor changes in PG synthetic activities. Results showed that PGHS-2 mRNA (4.0 kilobases) and protein (74000 Mr) were absent in preovulatory follicles isolated at the onset of estrus, low in follicles obtained 18 h after estrus (16.0 +/- 1.2 h post-LH surge), and markedly induced 24 h postestrus (20 +/- 0 h post-LH surge). Immunoblot and immunohistochemical analyses revealed that PGHS-2 protein was selectively induced in granulosa cells. Follicular fluid concentrations of PGE2 and PGF2alpha increased significantly (p < 0.01) between 0 and 24 h after estrus (from 2.8 +/- 0.2 to 87.9 +/- 30.9 ng/ml for PGE2; from 0.05 +/- 0.02 to 68.9 +/- 23.6 ng/ml for PGF2alpha). Collectively, these results clearly demonstrate that the induction of PGHS-2 in bovine preovulatory follicles is a physiological event that occurs after the endogenous LH surge.
Liu
J
J
Centre de recherche en reproduction animale, Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada.
Carrière
P D
PD
Doré
M
M
Sirois
J
J
D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D015237:Dinoprost / Q000032:analysis; D015232:Dinoprostone / Q000032:analysis; D004958:Estradiol / Q000032:analysis; D004971:Estrus; D005260:Female; D015571:Follicular Fluid / Q000737:chemistry; D015870:Gene Expression; D015151:Immunoblotting; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis / Q000235:genetics*; D007986:Luteinizing Hormone / Q000378:metabolism*; D006080:Ovarian Follicle / Q000201:enzymology*; D010060:Ovulation; D011374:Progesterone / Q000032:analysis; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis
D007527:Isoenzymes; D012333:RNA, Messenger; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D015237:Dinoprost; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone