Regulation of anion secretion by cyclo‐oxygenase and prostanoids in cultured epididymal epithelia from the rat

Abstract

The role of cyclo‐oxygenase (COX) in the regulation of anion secretion (measured as short‐ circuit current, Isc) in cultured epididymal epithelia from immature rats was investigated. COX inhibitors attenuated the increase of anion secretion caused by bradykinin (LBK) but had no effect on that caused by PGE2, suggesting that prostaglandin synthesis mediates the secretory response of the tissues to LBK. The apparent IC50 values for indomethacin, piroxicam and L‐745,337 in inhibiting the LBK‐induced Isc were 0·14, 1·34 and 15·7 μM, respectively. This order of potency: indomethacin > piroxicam > L‐745,337 >> DFU suggests the involvement of the COX‐1 isozyme in the mediation of the secretory response to LBK. Among the COX products (prostaglandins, thromboxane and prostacyclins) tested, only PGE2 and, to a much lesser extent, PGF2α stimulated anion secretion by cultured rat epididymal epithelia. The effect of PGE2 was mimicked by 11‐deoxyl PGE1, a specific prostaglandin E (EP)2/4 receptor agonist, but not by sulprostone, a specific EP1/3 receptor agonist, indicating that cyclic AMP‐coupled EP2/4 receptors are involved in the LBK‐stimulated anion secretion. A reverse transcriptase‐polymerase chain reaction study detected the expression of COX‐1 and COX‐2 mRNA in intact rat epididymis and in cultured epididymal epithelia. The expression of COX‐1 mRNA was reduced by LBK by 44 %. Immunohistochemical studies demonstrated the presence of COX‐1 immunoreactivity in the basal cells of the intact rat epididymis. By comparision, COX‐2 immunoreactivity was detected in the apical pole of the principal cells. The role of COX in the formation of the epididymal microenvironment and the implication of long term administration of non‐steroidal anti‐inflammatory drugs (NSAIDs) on male fertility are discussed.

The renin-angiotensin system and male reproduction: new functions for old hormones

“…Western blot analysis of angiotensinogen identified a single 60 kDa protein band similar to that observed for other tissues. Interestingly, renin mRNA has not been found in the epididymis (Leung et al 1999(Leung et al , 2000, despite the presence of renin-like activity in epididymal cell cultures (Wong & Uchendu 1991). This observation implies the presence of a non-classic RAS, at least in the epididymal epithelium, that uses alternate enzymes to renin.…”

“…The action of AngII on anion secretion is mediated by the stimulation of the prostaglandin PGE 2 (Leung et al 1998b). The expression of cyclooxygenase, a principal enzyme in prostaglandin synthesis, is controlled by testicular androgens (Wong et al 1999, Cheuk et al 2000. These data suggest that androgens control anion secretion in the epididymis by stimulating components of the RAS and of prostaglandin synthesis.…”

“…AngII (Zhao et al 1996), AT 1 and AT 2 receptors (Grove & Speth 1989, Leung et al 1997a have been localized to the epididymal epithelium. Angiotensinogen, the mandatory component for locally produced angiotensins, has been identified by Northern blot, PCR and Western blot (Leung et al 1999(Leung et al , 2000. It has been localized to the epithelium by immunohistochemistry and in situ hybridization histochemistry (Leung et al 1999).…”

“…Angiotensinogen, the mandatory component for locally produced angiotensins, has been identified by Northern blot, PCR and Western blot (Leung et al 1999(Leung et al , 2000. It has been localized to the epithelium by immunohistochemistry and in situ hybridization histochemistry (Leung et al 1999). Western blot analysis of angiotensinogen identified a single 60 kDa protein band similar to that observed for other tissues.…”

Differential modulation of bovine epididymal activity by oxytocin and noradrenaline

“…In accordance with the findings in several other species (Maggi et al 1987, Frayne & Nicholson 1998, Whittington et al 2001, Filippi et al 2002, OTR immunoreactivity could be localized to the peritubular muscle wall as well as to the epithelium of the bovine epididymal duct. In this context, the possibility was tested whether OT, in addition to directly stimulating the peritubular contractile cells, amplifies the synthesis of relaxing paracrine factors like NO and prostaglandin E 2 in the epithelial (basal) cells particularly at the level of the corpus and the cauda (p) (see Wong et al 1999, Lazarus et al 2002, Mewe et al 2006b). However, neither L-NAME nor 20 mM indomethacin (suggested to selectively block the COX-1 at this concentration) reversed the inhibitory OT effects in these regions, raising the question about other relaxation-inducing signalling pathways triggered by OT.…”