ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The regulatory pathways involved in the ATP-stimulated CI- secretion across rat epididymal epithelium were investigated by the short-circuit current (ISC) technique. Biphasic characteristic was observed in the ISC responded to ATP (0.01-10 m̈M). Inhibitor of P1 receptor, 8-phenyltheophylline (up to 100 m̈M), did not have any effect on both phases of the ATP-stimulated ISC. The order of potency for stimulation of the two phases in ISC was ATP〉ADP〉 AMP, adenosine, consistent with the presence of P2-purinoceptors. CI- channel blocker, disulfonic acid stilbene (DIDS, 300 m̈M), only inhibited the first peak of the ATP-stimulated ISC while diphenylamine-dicarboxylic acid (DPC, 1 mM) reduced both, indicating the involvement of different conductance pathways. DIDS was found to have an inhibitory effect on Ca2+-activated ISC (induced by ionomycin, 10 m̈M) but not cAMP-activated ISC (induced by forskolin, 1 m̈M) which could only be blocked by DPC. Both peaks of the ATP-activated ISC could be significantly inhibited by pretreatment with a Ca2+-chelating agent, BAPTA-AM (50 m̈M). An increase in cellular cAMP content upon stimulation of ATP was measured by radioimmunoassay. No significant increase in cAMP production was observed in cells stimulated with adenosine. The ATP-induced cAMP increase was prevented by pretreatment with BAPTA-AM (100 m̈M) indicating that cAMP production upon ATP stimulation was secondary to an increase in intracellular Ca2+ concentration. These results indicate that the ATP-stimulated CI- secretion could be mediated by Ca2+ and cAMP-dependent regulatory pathways giving rise to the biphasic nature of the ATP-induced ISC. © 1995 Wiley-Liss, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041640207
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