AJP - Renal Physiology, Vol 251, Issue 3 537-F546, Copyright © 1986 by American Physiological Society

ARTICLES

Effect of bumetanide on potassium transport and ionic composition of the arterial wall

H. Cantiello, J. Copello, A. Muller, L. Mikulic and M. F. Villamil

Bumetanide (B) (1 mM) decreased K content of dog carotid arteries (Ka) by 11-15%, K turnover (lambda 2) by 31%, and steady-state K fluxes (JK) by approximately 48%. The drug also reduced intracellular (ic) Cl, H2O, and occasionally ic Na. The half-maximal inhibitory concentration of B on JK was close to 40 microM. However, 10 microM still fully reduced ic K, Cl, and H2O but not ic Na. Replacement of external Cl by sulfate or nitrate mimicked the B effects on JK and reduced its capacity of inhibition by approximately 40 and approximately 80%, respectively. Replacement of Na by choline decreased Ka and JK by 90 and 96%, respectively, and rendered B totally ineffective. B also decreased Cl uptake and content of cultured vascular smooth muscle and ic Cl and H2O of whole arteries. Ouabain (Ou) (1 mM) decreased Ka 90%, accelerated lambda 2 four- to fivefold, and reduced JK 45%. Addition of B or removal of external Na or Cl in the presence of Ou returned lambda 2 to normal levels and reduced the residual JK by approximately 90% but failed to further decrease the Ka. According to these data, B mainly inhibits a coupled KCl passive self exchange plus a smaller active net KCl influx. Ou abolished the active component without affecting the passive self exchange. The presence of Na is necessary for the operation of the KCl-coupled self exchange, and Na gradients may provide the energy for the uphill KCl movements.

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