The effect of NH4Cl on Rb+ fluxes in resting and stimulated rat submandibular acinar cells.
Dispersed salivary acini isolated from the rat submandibular gland were incubated in a HEPES-buffered Krebs-Ringer solution or in the same buffer containing 20 mM NH4Cl and the accumulation and efflux of K+ were measured with the radiotracer 86Rb+, in the presence and absence of acetylcholine and of transport inhibitors. Exposure to NH4Cl caused a significant (greater than 50%) reduction in tracer accumulation. This effect was blocked by 0.1 mM bumetanide, but not by 1 mM ouabain. The effect of NH4Cl was, on the other hand, nearly additive with that of 1 microM acetylcholine. In cells preincubated with tracer, acute addition of NH4Cl caused a significant net efflux of isotope, so that the tracer content fell to 45% of the control value within 10 min. Bumetanide added to preloaded cells in the same fashion had no effect on tracer content and did not modify the efflux of 86Rb+ induced by 1 microM acetylcholine. However, this inhibitor essentially abolished the NH4Cl-induced tracer efflux. Exposure to NH4Cl during tracer loading did not appear to affect subsequent agonist-stimulated tracer efflux. These results suggest that: (1) the inhibition of K+ entry by NH4Cl is due to an effective competition by the NH4+ ion with Rb+ (and K+) for uptake via a bumetanide-sensitive Na+/K+/2Cl- contransporter.(ABSTRACT TRUNCATED AT 250 WORDS)
D000109:Acetylcholine / Q000494:pharmacology; D000641:Ammonia / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D018999:Charybdotoxin; D004123:Dimethylamines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008297:Male; D008744:Methylamines / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics*; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012414:Rubidium Radioisotopes; D012604:Scorpion Venoms / Q000494:pharmacology; D013363:Submandibular Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
D002087:Butyrates; D004123:Dimethylamines; D008744:Methylamines; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D012604:Scorpion Venoms; D000643:Ammonium Chloride; D002034:Bumetanide; D020148:Butyric Acid; D018999:Charybdotoxin; D010042:Ouabain; D000641:Ammonia; D001285:Atropine; C034516:dimethylamine; C027451:methylamine; C023336:trimethylamine; D000109:Acetylcholine; D011188:Potassium