BIOLOGICAL-ACTIVITIES OF CYSTIC-FIBROSIS SERUM .4. STIMULATION OF THE CALCIUM MEDIATED K+ EFFLUX FROM RAT SUB-MANDIBULAR GLAND FRAGMENTS

Cystic fibrosis (CF) and heterozygotes [human] 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 Ca channel blocker D600 and EGTA [ethylene glycol bis(.beta.-aminoethyl ether)-N,N,N'',N''-tetraacetic acid]. 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 Ca ionophore A23187 when added in the presence of D600. In addition, ultrafiltrates of CF serum (< 10,000 daltons) also stimulated K+ efflux from rat submandibular gland tissue fragments. CF serum factor(s) may be altering membrane permeability to Ca which results in the release of K+ from rat submandibular gland fragments.