DISCRETE STIMULATORY EFFECTS OF PLATELET-DERIVED GROWTH-FACTOR (PDGF-BB) ON LEYDIG-CELL STEROIDOGENESIS

The effect of platelet-derived growth factor-BB on adult rat Leydig ce ll steroidogenesis has been determined using culture conditions which maintain testosterone production and responsiveness to luteinising hor mone for 3 days. A significant stimulation of testosterone levels was observed in acute response to a maximally stimulating dose (8 ng/ml) o f rat luteinising hormone on the third day of culture, but was depende nt on pre-exposure of the Leydig cells to PDGF-BB for 2 days, whilst m aintained in the presence of a minimum dose (0.1 ng/ml) of rat luteini sing hormone. These data demonstrate a very discrete action of PDGF-BB on adult rat Leydig cell steroidogenesis in vitro, but whether or not this constitutes a significant paracrine effect in vivo remains to be established.