Androgens modulate growth hormone-releasing factor-induced GH release from bovine anterior pituitary cells in static culture

Abstract

Static primary cultures of bovine anterior pituitary (AP) cells were utilized to study the effect of sex steroids on basal growth hormone (GH) and GH-releasing hormone (GRF)-stimulated release of GH. The AP cells (5 × 10 5 cells/well) were allowed to attach for 72 hr and become confluent before treatments were imposed. Cells were incubated for an additional 24, 48 or 72 hr with either estradiol-17β (E 2, 10 −11 to 10 −8 M), testosterone (T, 10 −8 to 10 −5 M), dihydrotestosterone (DHT, 10 −9 to 10 −6 M) or 5α-androstane-3α, 17β-diol (3α-diol, 10 −11 to 10 −8 M). Media were collected every 24 hr and GH concentrations determined by RIA. Incubation of calf AP cells with gonadal steroids did not affect (P>0.05) basal GH released at 24, 48, or 72 hr. In another experiment, calf AP cells were incubated with the same concentrations of the steroids for 24 hr, media harvested, cells washed and challenged in serum-free media for 1 hr with bovine GRF 1–44-NH 2 (10 −8 M). In non-steroid treated wells, GRF increased (P<0.05) GH from 58 to 134 ng/ml. Incubation with E 2 or 3α-diol did not affect (P>0.05) GRF-induced GH release; however, preincubation with T (10 −5 M) and DHT (10 −9, 10 −8 and 10 −7 M) increased (P<0.05) GRF-induced GH release above control concentrations (195, 235, 190 and 185 ng/ml, respectively). At the doses tested, sex steroids did not affect basal release of GH, but androgens increased responsiveness of somatotropes to GRF.