Exocrine secretion of epidermal growth factor by the rat prostate: effect of adrenergic agents, cholinergic agents, and vasoactive intestinal peptide

Abstract

Perfusion of the rat prostatic urethra in vivo provided a means of collecting the rat prostatic secretory product. The secretion of the protein epidermal growth factor (EGF) was investigated by radioimmunoassay (RIA). Baseline secretion of EGF into prostatic fluid was less than .03 +/- .004 SEM ng/min. The alpha-adrenergic agonist phenylephrine caused an increase in EGF to 3.6 +/- .4 SEM ng per 30-min period. The stimulation was blocked completely by prazosin and only partially by yohimbine, indicating primarily alpha 1 control. One mg/kg IV phenylephrine produced a maximal response. The beta-adrenergic agonist isoproterenol caused no increased secretion of EGF. The cholinergic agonist pilocarpine stimulated EGF secretion to 3.2 +/- .6 SEM ng per 30-min period. Atropine blocked the cholinergic stimulation. The combination of phenylephrine and pilocarpine did not result in greater stimulation than either agent alone. Vasoactive intestinal peptide (VIP) did not stimulate EGF secretion, nor did it augment either pilocarpine or phenylephrine-stimulated secretion. EGF secretion into rat prostatic fluid is under both alpha 1-adrenergic and cholinergic control.