Electrophysiologically distinct cell types in human sweat gland secretory coil

The human sweat gland secretory coil consists of three histologically distinct cell types: myoepithelial (ME), light (or clear), and dark cells. The electrophysiological properties of all these cells are poorly defined. Employing electrophysiological techniques, we report distinct pharmacological responses of three different cell types from freshly isolated human sweat gland secretory coil. The superficial ME cells are characterized by 1) spontaneous depolarizing spikes (2 to 50 mV), 2) high cell membrane potentials [Vm = -68.6 +/- 3.9 (SE) mV; n = 21], 3) a K(+)-selective cell membrane (slope response = 54.2 +/- 6.7 mV per decade K+ concentration; n = 4), 4) depolarizing responses to cholinergic agonist mecholyl (delta Vm = 29.1 +/- 3.1 mV, n = 21), and 5) insensitivity to beta-adrenergic stimulation (n = 12). Two other types of cells, presumably secretory, were also observed. We arbitrarily labeled these cells as beta-adrenergic sensitive (beta-S) and beta-adrenergic insensitive (beta-I) cells based on their respective sensitivity to isoproterenol (IPR), a beta-adrenomimetic. Properties of the beta-S cells include 1) relatively higher basolateral membrane potentials (Vm = -57.3 +/- 3.1 mV; n = 13), 2) depolarizing responses to IPR (delta Vm = 16.8 +/- 2.6 mV; n = 9) inhibitable by the beta-adrenergic antagonist propranolol, and 3) hyperpolarizing responses to mecholyl (delta Vm = -21.8 +/- 2.0 mV; n = 13). The beta-I cells are characterized by 1) low basolateral membrane potentials (Vm = -23.6 +/- 2.1 mV; n = 16), 2) insensitivity to beta-adrenergic stimulation, and 3) hyperpolarizating responses to mecholyl (delta Vm = -16.1 +/- 2.1 mV; n = 16).