Effects of K+ channel blockers and K+ ionophore on isoprenaline-induced secretion of amylase from rat parotid acini

The involvement of K+ channels in regulating secretion of amylase from isolated rat parotid acini was studied in conjunction with P-adrenoceptor function. It was observed that increasing the concentration of extracellular K+ or adding K+ channel blockers enhanced the secretion of amylase. Among several K+ channel blockers, tetraethylammonium, apamin and charybdotoxin were effective to enhance secretion by 48, 69 and 84%, respectively. Glibenclamide was without effect. A low concentration of isoprenaline (10(-7) M) enhanced secretion by 154% and its simultaneous application with tetraethylammonium gave a synergistic effect, producing 371% stimulation. Combination of tetraethylammonium and a low concentration of carbachol (10(-6) M) did slot give the synergistic effect. Isoprenaline at the concentration of 10(-6) M enhanced secretion by 313% and this was reduced to 116% by 10(-5) M valinomycin, a K+ ionophore. Valinomycin was without effect on carbachol (10(-5) M)-induced secretion. Somatostatin (10-5 M) and morphine (10(-4) M) also reduced isoprenaline-induced secretion of amylase. These results suggested the regulation of Ca2+-activated K+ channels by isoprenaline in amylase secretory processes in parotid acini. (C) 1997 Elsevier Science B.V.