Calcium channel alterations in genetic hypertension.

We proposed earlier that voltage-dependent calcium (Ca2+) current is altered in single azygos venous cells from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). In this study, the effects of different intracellular concentrations of ethylene glycol-bis-N,N,N',N',-tetraacetic acid (EGTA) on Ca2+ currents were investigated. Vascular muscle cells from SHR and WKY rats were equilibrated with pipette solution containing 0.1 mM or 10 mM EGTA. Increasing the EGTA concentration from 0.1 to 10 mM in SHR vascular cells significantly enhanced the peak amplitude of the longer lasting (L) current from 87 +/- 12 pA to 152 +/- 8 pA, while the transient (T) current amplitude was not significantly different (52 +/- 7 pA and 36 +/- 7 pA, respectively). In WKY rat vascular muscle cells, the amplitudes of the T and L currents were not significantly different with the same comparison of intracellular EGTA concentrations. These observations suggest that relatively low intracellular Ca2+ concentrations can more strongly modulate Ca2+ current through the L channel in SHR than WKY rat vascular muscle cells.