CHARACTERIZATION OF VOLUME-ACTIVATED CHLORIDE CURRENTS IN ENDOTHELIAL CELLS FROM BOVINE PULMONARY ARTERY

摘要

We have measured the kinetic and pharmacological properties of volume-activated Cl- currents (I-Cl,I-vol) in endothelial cells, and tried to correlate them with those of the already described volume-activated current I-Cln. Both conductances show a similar permeability sequence for monovalent anions, and they are blocked by extracellular ATP. In the present report, we demonstrate by Western blot and RT-PCR that cultured endothelial cells from bovine pulmonary artery (CPAE) contain pI(Cln). The expression of this protein has been shown to be closely associated with the I-Cln current. I-Cl,I-vol showed however, in contrast with I-Cin, no striking inactivation at positive potentials. This property is also at variance with that of the volume-activated current related to MDR-1. Activation of I-Cl,I-vol at potentials more negative than -80 mV was not time dependent, which excludes a major contribution of a ClC-2 related current. The antiviral nucleoside analogue AZT (3'-azido-3'-deoxythymidine) inhibited I-Cl,I-vol by 21 +/- 2.7% (n = 10), at a concentration of 100 mu M. Another antiviral drug, acyclovir (ACV, 9-[(2-hydroxyethoxy)methyl] guanine) blocked l(Cl,vol) by 27 +/- 6.2% at 100 mu M (n = 11). Both blocking effects are much smaller than those reported for I-Cln. The phenol derivative gossypol, which blocks I-Cln-related currents, efficiently inhibited I-Cl,I-vol in CPAE cells (67 +/- 2.1% at 1 mu M, n = 7, K-1 = 0.4 mu M). The presence of pI(Cln) in CPAE cells and the similar qualitative pharmacological profile of l(Cl,vol) and I-Cin support the hypothesis that pI(Cln) is a good molecular candidate for I-Cl,I-vol in endothelial cells. The discrepant kinetic properties may indicate that these time-dependent currents at high positive or negative potentials are not intrinsic properties of the channels, but are caused by time-dependent depletion/accumulation phenomena due to the large amplitudes of these currents. [References: 31]