EVIDENCE OF 2 DISTINCT EPITHELIAL-CELL TYPES IN PRIMARY CULTURES FROM HUMAN SWEAT GLAND SECRETORY COIL

The human sweat gland secretory coil (SC) is comprised of myoepithelial (ME) and two types of secretory epithelial cells. The secretory cells include beta-adrenergic-sensitive (beta-S) cells [responsive to the beta-adrenergic agonist isoproterenol (IPR)] and beta-adrenergic insensitive (beta-I) cells. We have grown segments of SC in primary culture and found that under the conditions described here, only epithelial cells form outgrowths as indicated by morphological and physiological properties. As in the native SC epithelium, the secretory cells in primary culture were comprised of polygonal epithelial cells with a characteristic hyperpolarization of cell potentials (V(m)) to cholinergic stimulation by mecholyl (magnitude of change of V(m) = DELTA-V(m) = 21.5 +/- 1.3 mV, mean +/- SE, n = number of cells = 44). We have found both beta-S and beta-I cells as determined by unstimulated membrane potentials, sensitivity to IPR, and K+ conductance (G(K+)). The frequency distribution of unstimulated cells indicated two distinct populations of cells, one with high membrane potentials (V(m) = -63 +/- 2.6 mV), which correlated with beta-S cells, and a second with low membrane potentials (V(m) = -22 +/- 1.5 mV), which correlated with the beta-I cells. IPR depolarized the V(m) of beta-S cells (DELTA-V(m) = 11.0 +/- 0.8 mV, n = 25) without affecting the V(m) of beta-I cells. The effect of IPR on beta-S cells was blocked by the beta-adrenergic antagonist propranolol and mimicked by chlorophenylthio-adenosine 3',5'-cyclic monophosphate (CPT cAMP) (DELTA-V(m) = 11.0 +/- 2.5 mV, n = 6), indicating that the IPR response was mediated by beta-adrenergic receptors and intracellular cAMP. Both cell types were devoid of amiloride-sensitive Na+ conductance (G(Na+)) but exhibited both K+ (G(K+)) and Cl- (G(Cl-)) conductances. The existence of G(K+) and G(Cl-) was indicated by depolarization of the V(m) of these cells to a 10-fold increase in extracellular K+ ([K+]e) and inhibition of G(K+) by Ba2+ and the removal of extracellular Cl-, respectively. These results suggest that the expressed properties of cultured cells are compatible with properties of native secretory cells. We conclude that, although morphologically indistinguishable, both beta-S and beta-I cells grow in primary culture while retaining the progenitor cell properties and provide an ideal in vitro model for studying certain components of exocrine secretion.