AJP - Endocrinology and Metabolism, Vol 268, Issue 6 E1057-E1064, Copyright © 1995 by American Physiological Society

ARTICLES

Insulin-like growth factor binding protein-3 inhibits porcine granulosa cell function in vitro

S. E. Samaras and J. M. Hammond
Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA.

Recombinant human insulin-like growth factor binding protein-3 (rhIGFBP-3) effects on basal, insulin-like growth factor I (IGF-I)-, and follicle-stimulating hormone (FSH)-stimulated progesterone (P4) secretion and [3H]aminoisobutyric acid (AIB) uptake by primary porcine granulosa cells (MDGs) and MDGs that have been passaged once (MDGp1) were assessed. Cells were treated concurrently or were preincubated with rhIGFBP-3 followed by treatment. rhIGFBP-3 had no effect on MDG or MDGp1 cell numbers after 24 h. Cotreatment with rhIGFBP-3 inhibited P4 secretion after treatment with FSH, IGF-I, and FSH plus IGF-I. FSH did not stimulate [3H]AIB uptake. However, the IGF-I-stimulated increase in [3H]AIB uptake was completely prevented by concurrent treatment with IGFBP-3. Preincubation of MDGp1 cells with IGFBP-3 dose dependently inhibited FSH- and IGF-I-stimulated P4 secretion. This inhibition was associated with increased cell association of the binding protein and increased IGF-I binding to the cells. These results indicate that IGFBP-3 is inhibitory to a variety of crucial functions in porcine granulosa cells, supporting a role for it in the regulation of granulosa cell function.

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