COMPARATIVE REGULATION OF ALPHA(1)-ADRENERGIC RECEPTOR-MEDIATED CONTRACTION IN UROGENITALLY DERIVED SMOOTH-MUSCLE - EFFECT OF EPIDERMAL GROWTH-FACTOR

Contractility of smooth muscle within mammalian urogenital organ syste ms has an established role in physiological/pathophysiological functio ning of the component structures. Our aim was to examine the direct ef fect of epidermal growth factor (EGF) on smooth muscle tone as well as its indirect effects in regulating alpha(1)-adrenoceptor-mediated con traction of the prostate, the vas deferens and renal arteries. Tissues were mounted isometrically, under controlled conditions, and changes in tension in response to treatment with phenylephrine (PE) with or wi thout pretreatment with EGF were recorded on a physiological recorder via force transducers. In the rabbit prostate, EGF potentiated the mag nitude of contraction to PE. The potentiation appeared to be dependent on cycle-oxygenase products. In the human prostate, EGF potentiated t he contractile response to PE. EGF had no effect on the PE-induced con traction of the rabbit renal artery and vas deferens. EGF alone did no t alter smooth muscle tone in any of the above-mentioned tissues. The main finding of this study is the difference in the regulation by EGF of the alpha(1)-adrenoceptor-mediated response in smooth muscle of the prostate, from that by the vas deferens and renal artery. The reasons for this difference in response remain to be elucidated. This study m ay form the basis for further investigation into receptor transregulat ion and its relevance to symptomatic benign prostatic hyperplasia (BPH ).