Co-ordinate actions of FSH and insulin-like growth factor-I on LH receptor expression in rat granulosa cells.
The actions of FSH and Insulin-like growth factor-I (IGF-I) were studied in cultured rat ovarian granulosa cells. Cells became differentiated and expressed LH receptors when they were incubated for 72 h with 200 micrograms FSH/l (high FSH) but not 20 micrograms FSH/l (low FSH). Treatment with high but not low FSH increased the release of both immunoreactive and bioactive IGF-I into the medium. A combination of low FSH and IGF-I reproduced the effect of high FSH on LH receptor expression. We then examined the critical time when low FSH and IGF-I exerted their effects. In the presence of continuous low FSH, IGF-I was capable of inducing LH receptor expression even when added 24 h after the addition of low FSH. However, when IGF-I was added at 36 h, LH receptor expression measured at 72 h was greatly reduced. In contrast to the action of IGF-I, continuous exposure to low FSH was required for LH receptor expression, and IGF-I had no effect when FSH was not included for the entire 72 h of culture. DNA synthesis as assessed by both [3H]thymidine incorporation and nuclear bromodeoxyuridine labelling was moderate at the beginning of culture and markedly reduced at 24 h both in the presence and absence of either high FSH or low FSH plus IGF-I. In the presence of either high FSH or a combination of low FSH plus IGF-I, DNA synthesis remained decreased for up to 72 h whereas it began to increase in the absence of either high FSH or a combination of low FSH plus IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)
Kanzaki
M
M
Cell Biology Research Unit, Gunma University, Maebashi, Japan.
Hattori
M A
MA
Horiuchi
R
R
Kojima
I
I
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004357:Drug Synergism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011974:Receptors, LH / Q000378:metabolism*; D013997:Time Factors
D006063:Chorionic Gonadotropin; D011974:Receptors, LH; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone; D004247:DNA