The regulation of membrane 125I‐ and 86Rb+ permeability in a virally transformed cell line (NCL‐SG3) derived from the human sweat gland epithelium

Abstract

SUMMARYWe have explored the factors that may regulate membrane permeability in a cell line (NCL-SG3) derived from the human sweat gland epithelium. lonomycin increased the rate of 1251-efflux from preloaded cells and this action appeared to be due to an increase in intracellular free calcium ([Ca2+]). The ionomycin-evoked increase in 1251-efflux was reduced in cells that were exposed either to barium or to valinomycin in the presence of a high concentration of external potassium. It thus appears that a fraction of the ionomycin-evoked increase in 1251-efflux is due to the activation of potassium channels and experiments using 8"Rb+ also suggested that ionomycin increased the rate of potassium efflux, an effect which was totally abolished by barium. Blockade of Na+-K+-2Cl1-cotransport and of Cl--HCO exchange reduced the basal rate of 1251-efflux and the ionomycin-evoked increase in 1251-efflux from control cells and from cells depolarized by valinomycin. These transport systems thus contribute to anion efflux, although [Ca2+]-dependent chloride channels also appear to be present. Acetylcholine increases [Ca2+] [Ca2+]i, but this hormone did evoke cyclic-3',5'-adenosine monophosphate (cyclic AMP) production. However, membrane permeability was riot under adrenergic control, as the cells did not appear to express functional, cyclic AMP-dependent anion channels. This may be because they were not fully differentiated under the culture conditions. ATP consistently evoked a dose-dependent increase in anion efflux that appeared to be mediated by [Ca2+]i. The increase in [Ca2+]i was initiated by the release of calcium from a limited internal store and was subsequently sustained by calcium influx. UTP and ADP also increased [Ca2+]i, whereas adenosine, AMP and x,/i-methylene ATP were without effect. These data thus suggest that a subclass of type 2 purine receptor, which is functionally coupled to phosphoinositidase C, is present in these cells.

Regulation of Ion Content in Primary Cultures from Reabsorptive Ducts of Human Sweat Glands Studied by X-ray Microanalysis.

“…The present findings show that the Cl and K concentrations in cells from primary cultures from sweat gland ducts were sensitive to stimulation by ATP, but not by UTP. The effect of ATP on the Cl and K concentration has previously been shown in primary cultures from human sweat gland coils (18) and in a sweat gland cell line (30,31). Our findings show that ATP, carbachol, the Ca2+ ionophore A23187, and CAMPhad the same potency for activation of the loss of Cl from primary cultures of duct cells.…”

“…ATPcan increase Cl~permeability in isolated sweat glands, although the pharmacology of this response is not known (26,30). Extracellular ATP and UTP can increase intracellular free Ca2+ by releasing calcium from intracellular stores and sustaining subsequent calcium influx (16,30).…”

“…The rise in intracellular free Ca2+ appears to be mediated via a type 2-purine (P2) receptor (7,9). ATPcan also raise the cellular CAMP content, whereas UTPis ineffective (16,30) X-ray microanalysis can be used for the study of ion transport in cultured cells. The method has the advantage that changes in several different ions can be studied simultaneously, and that inhomogeneities in cell cultures can be easily revealed (27).…”

“…InsP3 enters the cytoplasm and releases Ca2+ from intracellular stores. The increase in intracellular free Ca2+ is sustained by calcium influx from the extracellular compartment (30). Sweat secretion can also be evoked by adrenergic agonists, but the response is generally smaller than that to responses of muscarinic agonists.…”

“…Extracellular ATP and UTP can increase intracellular free Ca2+ by releasing calcium from intracellular stores and sustaining subsequent calcium influx (16,30). The rise in intracellular free Ca2+ appears to be mediated via a type 2-purine (P2) receptor (7,9).…”