Effect of efferent duct ligation, gonadectomy and testosterone replacement on epididymal contractility in the rat.

The epididymis is an androgen-sensitive tissue which responds to even minor fluctuations in circulating androgens (Prasad, Rajalakshmi, Gupta & Karkun, 1973). Epididymal receptors for androgens have been demonstrated (Blaquier, 1971) and male sex hormones are required for epididymal growth and structural and functional maintenance (Benoit, 1926; Risley, 1963 ; Price & Ortiz, 1965). Apart from circulating androgen, the epididymis may have access to two other sources of male sex hormones: androgens are present in the testicular fluid entering the epididymis (see Setchell, 1970) and the epididymis might itself be capable of producing androgens (Inano, Machino & Tamaoki, 1969). Testosterone produced in the testis could pass from the pampiniform plexus to the internal spermatic artery and thence to the caput epididymidis directly or to the caudaepididymidis through anastomoses between branches of the internal spermatic and the vasal arteries (Einer\x=req-\ Jensen, 1974). Epididymal contractile activity is known to be dependent upon androgens, but the reports are contradictory. Risley (1959) found that, in orchidectomized rats, spontaneous contractility ceased in the caput and appeared in the cauda epididymidis. This activity was reversed to normal by giving testosterone. Martins, Valle & Porto (1940) also report that contractions in themore distal regions of the epididymis are inhibited by male sex hormones, but a stimulatory effect of testosterone on the spontaneous contractility of the isolated guinea-pig cauda epididymidis has been suggested (Da Silva e Souza, Gimeno & Gimeno, 1974). This is surprising because orchidectomy results in a pro¬ gressive decrease of cholinesterase activity (Risley, 1961) and disappearance of adrenergic terminals from the musculature of the cauda epididymidis (Norberg, Risley & Ungerstedt, 1967). In the present study, we examined the androgenic regulation of spontaneous contractility of the rat epididymis in vivo.