Interrelationships between follicle stimulating hormone and the growth hormone--insulin-like growth factor--IGF-binding proteins axes in human granulosa cells in culture.
As it has been hypothesized that IGF-binding proteins (IGFBPs) may have a role as autocrine/paracrine factors in regulating the local actions of the insulin-like growth factors (IGFs) in the ovary, we studied the production of the IGFBPs by human granulosa cells (GC) in culture and the role of IGFBP-3 in the modulation of ovarian cell responsiveness to IGF-I and FSH. To this purpose, human luteinizing GC were cultured in serum-free conditions for 24 h and subsequently submitted to increasing concentrations (2-8 nmol/l) of recombinant non-glycosylated or partially glycosylated IGF-BP-3 for 48 h, in the presence or absence of IGF-I, des(1-3)IGF-I- a truncated analog of human IGF-I with markedly reduced binding ability to IGFBPs - and FSH (5-20 mIU/ml). The results demonstrate that human GC release IGFBP-1-2 and -3 into the medium, and that FSH is able to inhibit this release, while GH is clearly inhibitory on IGFBP-1 and stimulatory on IGFBP-3. Both IGF-I and des(1-3)IGF-I significantly (p < 0.001) stimulate E2 production by human GC in culture in a manner comparable to that of FSH in the dose range used. Preincubation for 2 h at 22 C with IGFBP-3, to allow the formation of the IGF-IGFBP complex, drastically reduced the stimulatory effect of IGF-I but not that of des(1-3)IGF-I. IGFBP-3 was also able to inhibit the stimulatory effect of FSH. These data show that: i) the IGF peptide is less active when bound to IGFBP-3; ii) as IGFBP-3 does not affect the potency of des(1-3)IGF-I, its inhibitory action is exerted upstream of the membrane receptor binding; iii) as the action of IGFBP-3 is exerted by binding the IGF peptide, its inhibitory effect on FSH points out the role of the locally produced IGF-II in potentiating the FSH action on human GC.
Barreca
A
A
Dipartimento di Scienze Endocrinologiche e Metaboliche, DiSEM, University of Genova, Italy.
Artini
P G
PG
Cesarone
A
A
Arvigo
M
M
D'Ambrogio
G
G
Genazzani
A R
AR
Giordano
G
G
Minuto
F
F
D000328:Adult; D001345:Autoradiography; D015153:Blotting, Western; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000378:metabolism
D003432:Cross-Linking Reagents; D018972:Insulin-Like Growth Factor Binding Protein 3; D011994:Recombinant Proteins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone