Biological activities of cystic fibrosis serum. IV. Stimulation of the calcium mediated K+ efflux from rat submandibular gland fragments.

Cystic fibrosis (CF) and heterozygote sera stimulate a significant K+ efflux from rat submandibular gland fragments in the presence of 1 mM ouabain. This sensitive parameter can be maximally stimulated by as little as 0.5% CF serum and is inhibited by the calcium channel blocker D600 and EGTA. Specific receptor blockers propranolol, phenoxybenzamine or atropine do not inhibit the CF serum-stimulated K+ efflux and agonists do not supramaximally stimulate K+ efflux when added with serum. CF serum-induced K+ efflux did not result in the leakage of lactic dehydrogenase into the bathing media nor did it mimic the action of the calcium ionophore A23187 when added in the presence of D600. In addition, ultrafiltrates of CF serum (less than 10,000 daltons) also stimulated K+ efflux from rat submandibular gland tissue fragments.