Bumetanide-sensitive NaCl uptake in rabbit tracheal epithelial cells is stimulated by neurohormones and hypertonicity.
Loop diuretic-sensitive NaCl(K) cotransport plays a fundamental role in absorption and secretion of electrolytes in epithelial tissues. Cotransport activity was measured as uptake of 22Na, 36Cl, or 86Rb at 27 degrees C in isolated rabbit tracheal epithelial cells. Uptake of radiotracer was linear from 1 to 2 min after initiation of radiotracer transport. Bumetanide at 10 microM final concentration did not affect tracer uptake. The endogenous catecholamine l-epinephrine and alpha 2-adrenergic agent clonidine increased sodium and chloride uptake at least 5.5-fold. Bumetanide blocked sodium uptake by 85% and chloride uptake by 72%. 86Rb uptake was not affected by l-epinephrine, clonidine, or bumetanide. The alpha 2-adrenergic antagonist yohimbine blocked the effects of l-epinephrine and clonidine on 22Na and 36Cl uptake. In Ca(2+)-depleted transport medium, baseline levels of sodium and chloride uptake increased 3.8- and 2.4-fold, respectively, in a bumetanide-independent manner. Nevertheless, l-epinephrine and clonidine induced a net stimulation of sodium and chloride uptake similar to that found in Ca(2+)-replete medium. This response was reduced by bumetanide and yohimbine. The Ca(2+)-elevating agent ionomycin increased bumetanide-sensitive sodium and chloride uptake 7.2- and 6.2-fold, respectively. Replacement of chloride with gluconate or sodium with N-methyl-D-glucamine in the extracellular medium inhibited l-epinephrine and clonidine-stimulated bumetanide-sensitive sodium and chloride uptake, respectively. Osmotic shrinkage in hyperosmotic (500 mM NaCl with all other electrolytes at normal concentration) transport medium markedly increased bumetanide-inhibitable sodium and chloride uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
Liedtke
C M
CM
Department of Pediatrics, Rainbow Babies and Children Hospital, Cleveland, Ohio.
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology*; D003470:Culture Media; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006728:Hormones / Q000494:pharmacology*; D006982:Hypertonic Solutions / Q000494:pharmacology*; D015759:Ionomycin / Q000494:pharmacology; D007477:Ions; D009995:Osmosis; D011817:Rabbits; D012965:Sodium Chloride / Q000493:pharmacokinetics*; D013566:Sympathomimetics / Q000494:pharmacology; D014132:Trachea / Q000166:cytology / Q000378:metabolism*
D003470:Culture Media; D006728:Hormones; D006982:Hypertonic Solutions; D007477:Ions; D013566:Sympathomimetics; D002034:Bumetanide; D012965:Sodium Chloride; D015759:Ionomycin