Comparative capacitative calcium entry mechanisms in canine pulmonary and renal arterial smooth muscle cells.

Experiments were performed to determine whether capacitative Ca(2+) entry (CCE) can be activated in canine pulmonary and renal arterial smooth muscle cells (ASMCs) and whether activation of CCE parallels the different functional structure of the sarcoplasmic reticulum (SR) in these two cell types. The cytosolic [Ca(2+)] was measured by imaging fura-2-loaded individual cells. Increases in the cytosolic [Ca(2+)] due to store depletion in pulmonary ASMCs required simultaneous depletion of both the inositol 1,4,5-trisphosphate (InsP(3))- and ryanodine (RY)-sensitive SR Ca(2+) stores.

Heterogeneity of calcium stores and elementary release events in canine pulmonary arterial smooth muscle cells.

To examine the nature of inositol 1,4,5-trisphosphate (IP(3))-sensitive and ryanodine (Ryn)-sensitive Ca(2+) stores in isolated canine pulmonary arterial smooth cells (PASMC), agonist-induced changes in global intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured using fura 2-AM fluorescence. Properties of elementary local Ca(2+) release events were characterized using fluo 3-AM or fluo 4-AM, in combination with confocal laser scanning microscopy. In PASMC, depletion of sarcoplasmic reticulum Ca(2+) stores with Ryn (300 microM) and caffeine (Caf; 10 mM) eliminated subsequent Caf-induced intracellular Ca(2+) transients but had little or no effect on the initial IP(3)-mediated intracellular Ca(2+) transient induced by ANG II (1 microM).

Functional and molecular expression of volume-regulated chloride channels in canine vascular smooth muscle cells.

1. We examined the possibility of functional and molecular expression of volume-regulated Cl- channels in vascular smooth muscle using the whole-cell patch-clamp technique and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on cells from canine pulmonary and renal arteries. 2.

Effect of Na+ current on excitation-contraction coupling in ventricular myocytes of guinea pig heart.

We investigated the effect of Na+ current on the Ca2+ current and Ca2+ transients in cardiac myocytes. Myocytes were isolated from the ventricles of guinea-pig hearts by enzymatic dispersion. The membrane currents were recorded by the whole-cell voltage clamping.

Effect of sarcoplasmic reticulum Ca release into diadic region on Na/Ca exchange in cardiac myocytes.

The hypothesis that sarcoplasmic reticulum (SR) generates subsarcolemmal [Ca] higher than that in the bulk of sarcoplasm and that it affects the rate of Na+Ca exchange were tested. Voltage clamped cardiomyocytes of guinea-pigs and rats were stimulated by pre-pulses from a holding potential of -80 mV to -40 mV (20 ms) followed by 200 ms depolarizations to +5 mV. Single 5, 10, 20, 30, 50, 100 and 300 ms depolarizations were interposed between 200 ms pulses.