Regulation of ion content in primary cultures from reabsorptive ducts of human sweat glands studied by X-ray microanalysis

X-ray microanalysis was used to investigate whether cAMP- and/or Ca2+-activ ated regulation of chloride and potassium efflux is expressed in primary cu ltures of sweat gland duct cells. The effects of extracellular UTP and ATP on the duct cells, and the signalling system involved in the response to AT P was also studied. Primary cultures from duct cells: of human sweat glands responded to 1 mu M carbachol, 2 mu M of the Ca2+ ionophore A23187, or 5 m M 8-bromo-cAMP stimulation for 5 min, resulting in a decrease in cellular C 1 and K concentrations. 50 mu M 5-nitro-2-(3-phenylpropyl-1-amino)-benzoic acid (NPPB), a Cl- channel blocker, can inhibit the decrease in C1 concentr ation induced by cAMP, Extracellular (200 mu M) ATP caused a decrease of Cl and K in cultured duct cells, while (200 mu M and 2 mM) UTP was ineffectiv e. Both the phosphoinositidase C inhibitor U73122 (10 mu M) and the absence of extracellular Ca2+ abolished the ATP-induced decrease in Cl and K conte nt. Alloxan (1.25 mM), :an adenylate cyclase inhibitor, had an inhibitory e ffect on the response to ATP. The decrease in K, but not in C1, content in the cells elicited by ATP was blocked by prior incubation with 100 ng/ml pe rtussis toxin, indicating the coupling of ATP to pertussis toxin-sensitive G-proteins. In conclusion, both Ca2+- and cAMP-dependent Cl- permeability i s present in primary cultures from duct cells of human sweat gland. The res ponse to ATP can be mediated both by Ca2+- and by cAMP-dependent pathways, and is coupled to pertussis toxin-sensitive G-proteins.