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 beta-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 not 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 Ca(2+)-activated K+ channels by isoprenaline in amylase secretory processes in parotid acini.
Murayama
T
T
Department of Pharmacology, Osaka University, Faculty of Dentistry, Japan.
Miwa
Y
Y
Maeda
S
S
Morisaki
I
I
Saito
K
K
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D018847:Opioid Peptides / Q000494:pharmacology; D010306:Parotid Gland / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D018679:Cholinergic Agonists; D007476:Ionophores; D018847:Opioid Peptides; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D013004:Somatostatin; D002217:Carbachol; D000681:Amylases; D007545:Isoproterenol; D011188:Potassium