Immunolocalization of regulatory peptides and 5-HT in bovine male urogenital apparatus.

Specimens of testis, excurrent duct including the accessory genital glands and urethra throughout its extension were investigated in adult bovines, in order to immunohistochemically localize both the peptidergic innervation and the epithelial cell types belonging to the diffuse endocrine system (DES). Immunoreactivities to GRP, met- and leu-enkephalins, CGRP, NPY, substance P, VIP, somatostatin, beta-endorphin and 5-HT antisera were tested by means of a labelled streptavidin-biotin (LSAB) method. Such regulatory substances were found in components of the peripheral nervous system (nerve fibers in the connective and muscular tissues, sub- and intrapithelial nerve terminals, nerve cells bodies and fibers in intramural ganglia), and in epithelial endocrine/paracrine cells. Bovine urogenital apparatus is supplied by many peptide-containing nerves, which contain in many localizations GRP and enkephalins, and to a lesser extent substance P, CGRP, NPY and VIP. A thin network of peptidergic nerves distributes to the musculature of the canalicular organs and accessory glands. The prostatic complex was especially rich in peptidergic innervation, and also contained somatostatin- and 5-HT-secreting endocrine cells. In addition, 5-HT-immunoreactive endocrine cells were found in the bulbourethral gland and urethral epithelium. CGRP-ir nerves were present contacting striated muscle fibers of urethra (motor end plates). The testis was devoid of any immunoreactivity. These data are compared with those obtained in a companion study carried out the same organs in two species of Equidae (Equus caballus and Equus asinus). Different patterns of immunoreactivities can be outlined in these domestic ungulates.