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pubmed:abstractText |
1. Isolated human eccrine sweat glands were cultured in vitro. Cells were harvested and plated onto permeable supports to form confluent cell sheets, area 0.2 cm2. These were used to study the electrogenic transepithelial transport of ions by measurement of short-circuit current (SCC). Epithelial sheets had a basal SCC of 5.89 +/- 0.62 microA cm-2 (n = 33) and a transepithelial resistance of 74.1 +/- 5.6 omega cm2 (n = 33). The transepithelial potential difference varied between -0.2 and -1.8 mV with a mean value of -0.71 +/- 0.09 mV (n = 33). 2. The basal current was abolished by addition of 10 microM-amiloride to the apical bathing solution. The concentration of amiloride which inhibited basal SCC by 50% (EC50) was 0.4 microM. Cultures prepared from the secretory coil of sweat glands, rather than from whole glands, were similarly sensitive to amiloride (EC50 = 0.8 microM). 3. Lysylbradykinin (LBK), carbachol, isoprenaline, prostaglandin E2 (PGE2) and A23187 all increased SCC in cultures from whole glands. LBK responses were obtained with basolateral and not with apical application. Furthermore LBK actions were not substantially altered by cyclo-oxygenase inhibition but showed marked desensitization upon repeated application. Sheet cultures prepared from sweat gland coils also showed SCC responses to both carbachol and LBK. Forskolin, an activator of adenylate cyclase, did not alter SCC in either type of preparation. 4. Replacement of chloride and of chloride and bicarbonate in the bathing solution did not cause attenuation of the responses to LBK or carbachol in whole-gland sheet cultures. Furthermore responses were unaffected by piretanide or acetazolamide. These results were taken to indicate that anion secretion was not the basis for the SCC responses. 5. Responses to LBK and carbachol were significantly reduced by amiloride (10 microM), this effect being reversible. No responses to LBK or carbachol were seen when N-methyl-D-glucamine (NMDG) was used to replace sodium, whereas reintroduction of sodium ions restored responsiveness to these agents. 6. The SCC responses to the muscarinic agonist carbachol and to LBK appear to be due to stimulation of amiloride-sensitive, electrogenic sodium absorption in whole-gland sheet cultures. Further it would appear that, in culture, the pleuripotential capacity of the cells is revealed since both whole-gland and secretory coil cultures exhibit some properties usually associated in vivo with duct cells. Many mammalian epithelia show electrogenic chloride secretion both in response to carbachol and LBK but also in response to activation of adenylate cyclase with forskolin.(ABSTRACT TRUNCATED AT 400 WORDS)
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