Interactions between follicle-stimulating hormone and growth factors in modulating secretion of steroids and inhibin-related peptides by nonluteinized bovine granulosa cells.
The aim was to investigate potential interactions between FSH and intraovarian growth factors in modulating secretion of inhibin A (inh A), activin A (act A), follistatin (FS), estradiol (E2), and progesterone (P4) by bovine granulosa cells cultured under conditions in which a nonluteinized FSH-responsive phenotype is maintained. Cells from 4- to 6-mm follicles were cultured in serum-free medium containing insulin (10 ng/ml) and androstenedione (10(-7) M), and effects of ovine FSH (0.037-3 ng/ml) were tested alone and in combination with insulin-like growth factors (IGF) (LR3 IGF-I analogue; 2-50 ng/ml) and epidermal growth factor (EGF; 0.1-10 ng/ml). Medium was changed every 48 h and cultures ended after 144 h, when cell number was determined. Between 48-96 h and 96-144 h, FSH promoted (P < 0.0001) increases in output of inh A (6-fold), act A (15-fold), FS (6-fold), and E2 (18-fold), with maximal responses (in parentheses) elicited by 0.33 ng/ml FSH during the final period. Higher FSH doses (1 and 3 ng/ml) gave reduced responses for each of the above hormones, whereas P(4) output was maximal (3-fold) at these doses. FSH promoted a slight increase in cell number ( approximately 1.7-fold; P < 0.001). LR3 IGF-I alone markedly increased (P < 0.0001) output of inh A (8-fold), act A (41-fold), FS (12-fold), and E2 (18-fold); this was accompanied by modest increases (P < 0.01) in P4 output ( approximately 2.5-fold) and cell number ( approximately 2-fold). Whereas FSH enhanced inh A, act A, FS, and E2 secretion evoked by lower doses of LR3 IGF-I, it suppressed (P < 0.001) the response to the highest dose. EGF alone promoted a 1.7-fold increase in cell number (P < 0.001) without affecting hormone release; however, it abolished (P < 0.001) FSH-induced secretion of inh A, act A, FS, and E2. Both FSH alone and LR3 IGF-I alone dose-dependently increased the act A:FS ratio ( approximately 3-fold; P < 0.005) and act A:inh A ratio (3-fold to 6-fold; P < 0.001), suggesting that both factors selectively raise activin "tone" and that this could be a key requirement for FSH and IGF-induction of follicular E2 production. This hypothesis was reinforced by the finding that addition of FS, to reduce the act A:FS ratio and sequester secreted activin, markedly suppressed (P < 0.001) FSH (3-fold)-, and LR3 IGF-I (2-fold)-induced E2 output.
Glister
C
C
School of Animal and Microbial Sciences, The University of Reading, Whiteknights, Reading RG6 6AJ, United Kingdom.
Tannetta
D S
DS
Groome
N P
NP
Knight
P G
PG
D028341:Activins / Q000032:analysis / Q000378:metabolism; D000735:Androstenedione / Q000494:pharmacology; D000818:Animals; D002417:Cattle / Q000502:physiology*; D002452:Cell Count; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004347:Drug Interactions; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D038681:Follistatin; D006107:Granulosa Cells / Q000187:drug effects* / Q000502:physiology; D006133:Growth Substances / Q000494:pharmacology*; D028322:Inhibin-beta Subunits / Q000032:analysis / Q000378:metabolism; D007265:Inhibins / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives* / Q000494:pharmacology; D011374:Progesterone / Q000378:metabolism; D013256:Steroids / Q000378:metabolism*
D016895:Culture Media, Serum-Free; D038681:Follistatin; D006133:Growth Substances; D007328:Insulin; C084339:LR(3)IGF-I; D013256:Steroids; C422405:activin A; C422362:inhibin A; D028341:Activins; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D007265:Inhibins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone; D028322:Inhibin-beta Subunits