Human chorionic gonadotropin-dependent regulation of 17beta-hydroxysteroid dehydrogenase type 4 in preovulatory follicles and its potential role in follicular luteinization.
17Beta-hydroxysteroid dehydrogenase type 4 (17betaHSD4) has a unique multidomain structure, with one domain involved in 17beta-estradiol inactivation. The objective of the study was to investigate the regulation of 17betaHSD4 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The equine 17betaHSD4 cDNA was cloned and was shown to encode a 735-amino acid protein that is highly conserved (81-87% identity) compared with other mammalian orthologs. RT-PCR/Southern blot analyses were performed to study the regulation of 17betaHSD4 transcripts in equine preovulatory follicles isolated between 0-39 h after hCG treatment. Results showed the presence of basal 17betaHSD4 mRNA expression before hCG treatment, but an increase was observed in follicles obtained 24 h after hCG (P < 0.05). Analyses of isolated preparations of granulosa and theca interna cells identified basal mRNA expression in both layers, but granulosa cells appeared as the predominant site of follicular 17betaHSD4 mRNA induction. A specific polyclonal antibody was raised against a fragment of the equine protein and used to study regulation of the 17betaHSD4 protein. Immunoblots showed an increase in full-length 17betaHSD4 protein in follicles 24 h after hCG (P < 0.05), in keeping with mRNA results. Immunohistochemical data confirmed the induction of the enzyme in follicular cells after hCG treatment. Collectively, these results demonstrate that the gonadotropin-dependent induction of follicular luteinization is accompanied by an increase in 17betaHSD4 expression. Considering the estrogen-inactivating function of 17betaHSD4, its regulated expression in luteinizing preovulatory follicles appears as a potential complementary mechanism to reduce circulating levels of 17beta-estradiol after the LH surge.
Brown
Kristy A
KA
Centre de Recherche en Reproduction Animale, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada J2S 7C6.
Boerboom
Derek
D
Bouchard
Nadine
N
Doré
Monique
M
Lussier
Jacques G
JG
Sirois
Jean
J
D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D005498:Follicular Phase / Q000378:metabolism*; D006736:Horses; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D034461:Luteinization / Q000502:physiology*; D008969:Molecular Sequence Data; D006080:Ovarian Follicle / Q000201:enzymology*; D012333:RNA, Messenger / Q000378:metabolism; D014018:Tissue Distribution
D006063:Chorionic Gonadotropin; D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase