Regulation of plasminogen activator secretion in Sertoli cells of the calf testis

Abstract

Sertoli cells isolated by enzyme dispersion from the testes of 3–4-month-old Hereford calves were maintained in culture for up to four days. Cells were incubated with a range of hormones and growth factors in serum-free media to determine which of these agents control the production of plasminogen activator (PA), a protease secreted by Sertoli cells which plays a pivotal role in germ cell migration and development. Basal levels of PA secretion by Sertoli cells were low (1–2 IU/mg cell protein) and were significantly ( P < 0.01) stimulated, i.e. 4–6 fold by bovine follicle-stimulating hormone (FSH; half-maximal response (ED 50)=215 ng USDA-bFSH-B1/ml) and the more purified ovine FSH (ED 50=9 ng NIADDK-oFSH-16/ml). A 10-fold elevation in PA secretion was also evoked using the nucleotide analogue 8-bromo-cyclic adenosine monophosphate (8Br-cAMP; ED 50=0.5 mmol/l) indicating the effect was mediated via FSH activation of adenylate cyclase. Epidermal growth factor (EGF; > 20 ng/ml) and retinol (> 100 ng/ml) induced significant ( P < 0.05) PA elevations of a lesser magnitude (up to 164%) and augmented the PA response to bovine FSH. Minor but significant ( P < 0.05) increases in PA secretion were also evoked using high doses of insulin (20 IU/ml), glucagon (2 μg/ml), testosterone (> 250 nmol/l), 5α-dihydrotestosterone (500 nmol/l) and by oestradiol-17β (> 0.8 nmol/l). No significant changes in PA secretion were induced by bovine luteinizing hormone (< 50 ng NIAMMD-bLH-4/ml), prolactin (< 100 ng NIAMMD-bPRL-6/ml) or by progesterone (< 1.25 μmoles/l). No androgen-binding protein was detected in medium conditioned by Sertoli cells following any of the treatments.