Differing luminal potential difference of cystic fibrosis and control sweat secretory coils in vitro

Transepithelial potential difference (PD) of isolated segments of the secretory coil of both human control and cystic fibrosis (CF) eccrine sweat glands was measured during stimulation with methacholine (MCh) and isoproterenol (ISO) in vitro. Negative luminal PD of about 10 and 16 mV developed across the secretory coil epithelium in control and CF secretory coil, respectively, during maximal MCh stimulation. ISO (10(-5) M) stimulation generated a mean of 1.9-mV negative luminal PD in control glands; however, ISO failed to enhance the luminal PD beyond the resting level of 0.9 mV in the CF secretory coil. The inhibition of ISO-induced (10(-5) M) luminal PD in control secretory coil by propranolol (5 X 10(-5) M) but not by atropine (10(-5) M) indicated its pharmacologic specificity. The possibility is discussed that this lack of electrical driving force during ISO stimulation could be one of the mechanisms for the absence of sweating response to beta-adrenergic stimulation in CF sweat glands reported recently (8). The mechanism for the higher MCh-induced luminal PD in the CF secretory coil remains to be studied.