ISSN:
1432-1424
Keywords:
Na-K-Cl cotransport
;
Nasal gland
;
Acetylcholine
;
Intracellular Na
;
Intracellular Ca
;
Calmodulin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract 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 μm 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 tetraacetoxymethyl ester. Addition of 1μm 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. The present results suggest that the ACh-induced increase in [Na+]i, mainly responsible for activation of Na-K-Cl cotransport, is mediated by a Ca2+/calmodulin-dependent phosphorylation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00233950
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