Cellular mechanisms in activation of Na-K-Cl cotransport in nasal gland acinar cells of guinea pigs.

The cellular regulation mechanism of Na-K-Cl cotransport was studied in dispersed acinar cells of the guinea pig nasal gland by a microfluorimetric imaging method using the Na(+)-sensitive dye sodium-binding benzofuran isophthalate. Addition of 1 micron acetylcholine (ACh) induced an immediate increase in intracellular Na+ concentration ([Na+]i) by 36.7 +/- 9.9 mM, which was almost completely abolished by the addition of atropine. The increased [Na+]i after cholinergic stimulation was due to the external (Cl-)-dependent cotransport system (about 80% of the total Na+ influx) and the dimethyl amiloride-sensitive (Na+)-H+ exchange system (of about 20%). The ACh-induced increase in [Na+]i was dependent on extracellular Ca2+ and was prevented by pretreatment with 8-(N, N-diethylamino)octyl-3,4,5-trimethoxybenzoate or O-O'-bis(2-aminophenyl)ethyleneglycol-N, N, N', N'-tetraacetic acid tetraacetoxymethylester. Addition of 1 microns ionomycin mimicked the ACh-induced increase in [Na+]i which was dependent on external Cl-. Moreover, both a calmodulin antagonist trifluoperazine and a myosin light chain kinase inhibitor ML-7 reduced the ACh-induced response in [Na+]i. However, the following treatment did not affect the basal [Na+]i nor the ACh-induced increase in [Na+]i: (i) addition of dibutyryl cAMP, 8-Br-cGMP, or phorbol 12-myristate 13-acetate, (ii) pretreatment of protein kinase inhibitors, H-89, H-8, H-7 or chelerythrine, (iii) prevention of cytosolic Cl- efflux by the addition of diphenylamine-2-carboxylic acid or, (iv) prevention of cytosolic K+ efflux by the addition of charybdotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)