ON TESTIS AND EPlDlDYMlS OF RATS - Pondicherry University ...

(Skinner and Fritz. 1985) and provided a potential mode of action for androgens to
regulate Sertoli cell function indirectly (Skinner, 1987). Supprcssion of scrum 131 I
concentration has been achieved following inhibin administration to castrated rats
suggesting the feedback regulation of FSH secretion by inhibin (Robertson el ul..
1991). Activin has been shown to stimulate LH release and circulating FSll
concentration in macaques and rats in vivo (Schwall er al, 1989; McLachlan el al.,
1989). Leydig cells have been shown to secrete oxytocin-like immunoreactive
material to influence the contractibility of the seminiferous tubules by acting on
peritubular cells (Worley et al.. 1984).
Rat germ cells co-cultured with rat Sertoli cells produce an inhibited RNA and
DNA synthesis of Sertoli cells (Rivarola el al.. 1985) as well as an increased secretion
of androgen binding protein (ABP). transferrin and inhihin and an inhihition 01' Scrtoli
cell aromatase activity (Le Magueresse and Jegou, 1988). The number of factors
implicated in paracrine regulation of testicular functions has been steadily increasing
and many factors have been shown to be of potential or proven physiological
significance (for review, see Spiteri-Grech and Nieschlag, 1993; Griswold, 1993).
1.1.2 Structure and functions of epididymis
Iipididymis is composed of a single, long. highly coiled duct closcly applied to
the surface of the testis and embedded in a variahle amount of adiposc tissue of
epididymal fat pad. It has been reported that mammalian epididymis. histologically
and functionally, can be divided into initial and middle segments where sperm
maturation takes place and a terminal segment, which subserves the function of sperm
storage (for review. see Robaire er 01.. 2000). Most abundant cell type found in the
epididymal epithelium is the principal cell, which has prominent stereocilia that
extend into the lumen. In rats, principal cells constitute 80% of the total epithelial cell
population in the initial segment and this number gradually decreases to 65% in the
cauda epididymis (Robairr and Hermo. 1988; Jones. 1999). Large numbers of
proteins arc secreted in the epididymis and the anterior par? of it has been shown to be