Properties of cAMP-dependent and Ca(2+)-dependent whole cell Cl- conductances in rat epididymal cells

Abstract

Single rat epididymal cell studied under whole cell patch-clamp condition responded to 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) (500 microM) and to ionomycin (1 microM) by an increase in whole cell conductance. A major part of the stimulated current was carried by Cl-, although a small part was due to nonselective cation current. After elimination of the cation current component by using impermeant cation, the cells revealed different Cl- conductance properties in response to adenosine 3',5'-cyclic monophosphate (cAMP) and ionomycin. The cAMP-stimulated Cl- conductance was independent of time and voltage and showed a linear current-voltage relationship. The anion permselectivity was NO3- > Br- > Cl- approximately I- >> SO(4)2-. The ionomycin-stimulated Cl- conductance showed marked time and voltage dependency. In contrast to the cAMP-induced anion permselectivity, the ionomycin-induced anion permselectivity was I- > Br- approximately NO3- > Cl- >> SO(4)2-. These results indicate that the epididymal epithelial cells exhibit different Cl- conductances sensitive to cAMP and Ca2+. The cAMP-activated conductance has properties resembling the type associated with the cystic fibrosis transmembrane conductance regulator found in cystic fibrosis-affected epithelia. This finding supports the notion that the epididymis is a cystic fibrosis epithelium.

Regulated anion secretion in cultured epithelia from Sertoli cells of immature rats

“…The intracellular Ca¥ was buffered to 100 nÒ. whole-cell current observed in rat Sertoli cells are consistent with a Ca¥-activated Cl¦ current, previously found in other Cl¦ secreting epithelia (Chan et al 1992;Huang et al 1993).…”

“…Current recordings were obtained using the whole-cell patch-clamp technique as described by Hamill and others (Hamill et al 1981) with a patch-clamp amplifier (Axopatch_200 or Axopatch_1D, Axon Instruments). Patch pipettes, made from borosilicate glass (Vitrex, Modulohm IÏS, Herlev, Denmark), were prepared as previously described (Huang et al 1993). They had a resistance of 2-6 MÙ.…”

Effect of neonatal exposure to estrogenic compounds on development of the excurrent ducts of the rat testis through puberty to adulthood.

“…It is well established that patients with CF are often infertile due to degeneration of the vas deferens, but some also suffer from obstructive azoospermia due to the deposition of thick mucous material in the epididymal lumen (37,38). There is evidence that a cAMP-activated C1-channel exists in the epididymal epithelium (39,40). Also, in situ hybridization studies on human tissue have localized the mRNA of this protein to the epididymis and vas deferens, with the highest expression in the head of the epididymis (41), raising the likelihood of its expression also in the efferent ducts.…”

Different regulatory pathways involved in ATP‐stimulated chloride secretion in rat epididymal epithelium

“…First, the biphasic rise in ATP-induced Isc can be differentially inhibited by different C1-channel blockers, indicating the final effectors mediating the ATP-stimulated C1-secretion are different types. Different t pes of C1-channels, namely, CAMP-activated, Car+-activated, and swelling-induced, have been characterized in a number of epithelial cells including the epididymal cells (Cliff and Frizzell, 1990;Chan et al, 1992Chan et al, , 1993Huang et al, 1993). These different channels have been reported to show different sensitivity to C1-channel blockers such as DIDS and DPC.…”