Ovarian receptors for insulin and insulin-like growth factor I (IGF-I) and effects of IGF-I on steroid production by isolated follicular layers of the preovulatory coho salmon ovarian follicle.
In this study, receptors for insulin and insulin-like growth factor I (IGF-I) in isolated theca-interstitial layers and granulosa cells of the coho salmon preovulatory ovary were characterized, and the effects of IGF-I on ovarian steroidogenesis were examined. Specific receptors for insulin and IGF-I were found in granulosa and theca-interstitial layers. In both follicular layers, IGF-I receptors were greater in number and higher in affinity than insulin receptors. The effects of IGF-I on in vitro production of testosterone (T) and 17 alpha-hydroxyprogesterone (17OH-P) by theca-interstitial layers and of 17 beta-estradiol (E2) and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) by granulosa cell layers were evaluated during the preovulatory period. Both human and salmon recombinant IGF-I inhibited the basal and GTH II-stimulated T and 17OH-P production by theca-interstitial layers throughout the preovulatory period. In contrast, IGF-I stimulated the production of both E2 and 17,20 beta-P by granulosa cell layers prior to germinal vesicle breakdown (GVBD) but only stimulated the production of 17,20 beta-P by granulosa cell layers after GVBD. The inhibitory effects of IGF-I on steroid production by the theca-interstitial layer and the opposite stimulatory effects on steroid production by the granulosa cell layer, coupled by the presence of specific IGF-I receptors in both follicular layers, suggest that IGF-I may play a role in the regulation of steroidogenesis in the preovulatory coho salmon ovary.
Maestro
M A
MA
Department of Biochemistry and Physiology, University of Barcelona, Spain.
Planas
J V
JV
Moriyama
S
S
Gutiérrez
J
J
Planas
J
J
Swanson
P
P
D000818:Animals; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D007700:Kinetics; D008024:Ligands; D017684:Oncorhynchus kisutch / Q000378:metabolism*; D006080:Ovarian Follicle / Q000378:metabolism*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010060:Ovulation / Q000502:physiology; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D013256:Steroids / Q000096:biosynthesis*; D013799:Theca Cells / Q000378:metabolism
D007457:Iodine Radioisotopes; D008024:Ligands; D011994:Recombinant Proteins; D013256:Steroids; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin