Blockage of Ca-activated Cl conductance by furosemide in rat lacrimal glands.

Single cells isolated from rat lacrimal glands were studied with the tight-seal whole-cell recording technique. It was found that furosemide (1 mM, applied externally) selectively blocked one part of the electrical response elicited by muscarinic agonists. This component of the response had been shown in a previous work (Marty et al. 1984) to be due to Ca-dependent Cl channels. The action of furosemide was further studied on cells which were dialysed with a high-Ca, high-Na solution, and which mainly displayed the Ca-dependent Cl conductance. In these experiments, furosemide (1 mM) was again found to depress the Ca-dependent Cl current. The present findings offer an explanation for previous reports that furosemide blocks ion fluxes and electrolyte secretion in exocrine glands without necessarily involving the neutral Na-K-Cl carrier usually assumed to be affected by the drug.