Epidermal growth factor receptor play important role in the spontaneous contractions of the cauda epididymis in castrated male adult rats

Epidermal growth factor receptor play important role in the spontaneous contractions of the cauda epididymis in castrated male adult rats

Agati, L.B., Kiguti, L.R.A., Godinho, R.O., Avellar, M.C.W. Department of Pharmacology, Section of Experimental Endocrinology, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil.

Introduction: It has been previously shown that castration of male rats increase spontaneous response of reproductive organs. Alpha1-adrenoceptors in the cauda epididymis mediate most of the smooth muscle contraction in this organ. Agonists of G-protein– coupled receptors (eg, adrenoceptors and angiotensin receptors) signal, at least in part, through matrix metalloproteinases (such as matrix metalloproteinase [MMP]-7) that transactivate the epidermal growth factor receptor (EGFR). Previous studies from our laboratory have shown the immunolocalization of EGFR and its activated form (pEGFR) in the epithelial and interstitial cells along epididymis from intact Wistar rats. After surgical castration, an increase in the immunolocalization of EGFR and pEGFR was observed in the smooth muscle cells from the cauda region, an effect reversed by testosterone treatment of the animal. The present study was designed to confirm the contractile response of EGF in cauda epididymal tubules and its correlation with spontaneous contraction in castrated male rats. Methods: All the experimental procedures described here were approved by our institutional ethics committee (process number 0921/6 and 0703/07). Control and surgically castrated (7 days) adult male Wistar rats (90 d) were used. Tubules from the cauda epididymis were isolated and mounted in 2 ml organ baths with nutritive solution (30oC) under 1.0 g of tension. The effects of the EGFR agonist (EGF, 100 ng/ml) and antagonist (AG1478, 20µM) on the spontaneous contractions recorded in control or castrated tissues were evaluated. Results: EGF induced no contractile effects in cauda tubules from