The norepinephrine-sensitive Ca2+-storage site differs from the caffeine-sensitive site in vascular smooth muscle of the rat aorta.

Using microfluorometry of quin 2, a Ca2+-sensitive dye, we characterized the release and uptake of Ca2+ by the norepinephrine-sensitive Ca2+-storage site and the caffeine-sensitive one. The norepinephrine-sensitive Ca2+-storage site was readily depleted in Ca2+-free medium and almost completely replenished by loading with 1.0 mM Ca2+ solution for 3 min, whereas the caffeine-sensitive site was scarcely affected. Furthermore, norepinephrine has little effect on the caffeine-sensitive Ca2+-storage site in Ca2+-free medium, and vice versa. We conclude that the location and mechanisms of release and uptake of Ca2+ of these two Ca2+-storage sites differ in the case of rat aortic vascular smooth muscle cells in primary culture.

Adenosine decreases intracellular free calcium concentrations in cultured vascular smooth muscle cells from rat aorta.

Using an intracellularly trapped dye, quin 2, effects of adenosine on intracellular free calcium concentrations ([Ca2+]i) were recorded, microfluorometrically, using rat aortic medial vascular smooth muscle cells (VSMCs) in primary culture. Regardless of whether cells were at rest (in 5 mM K+), at K+-depolarization (in 55 mM K+) or at Ca2+ depletion (in Ca2+-free media), adenosine induced a rapid reduction of [Ca2+]i, following which there was a gradual increase to pre-exposure levels, in cells at rest and in the case of Ca2+ depletion. Only when the cells were depolarized (55 mM K+) did adenosine induce a new steady [Ca2+]i level, lower than the pre-exposure value. These findings indicate that decrease in [Ca2+]i by adenosine is one possible mechanism involved in the adenosine-mediated vasodilatation, and that adenosine decreases [Ca2+]i by direct extrusion, by sequestration, or by inhibiting the influx of Ca2+ into VSMCs.

Ketanserin blocks alpha 1-adrenoceptors of porcine vascular smooth muscle cells.

The effect of ketanserin on alpha-adrenoceptors was studied in membrane preparations of the porcine aorta using [3H]prazosin and [3H]yohimbine binding assays to identify alpha 1- and alpha 2-adrenoceptors. Ketanserin bound to alpha-adrenoceptors and the Ki value of ketanserin for alpha 1-adrenoceptors was 8.3 nM, a value practically equal to that of phentolamine (Ki = 7.2 nM). The Ki value of ketanserin for alpha 2-adrenoceptors was 3.3 microM. Thus, at the doses prescribed clinically, ketanserin blocks alpha 1- but not alpha 2-adrenoceptors of porcine vascular smooth muscle.

Acyclovir-resistant herpes zoster encephalitis successfully treated with vidarabine: a case report.

A 78-year-old man developed herpes zoster virus (HZV) encephalitis. Initially, treatment with aciclovir (750 mg per day) improved CSF cell count and protein level. During the treatment, however, encephalitis in the patient deteriorated in spite of the treatment with aciclovir, suggesting that HZV in the patient had become resistant to aciclovir. Subsequent treatment with vidarabine (600 mg per day, for 15 days) resulted in dramatic improvement in CSF pleocytosis. About two months after the discontinuation of vidarabine, the CSF cell count was normal. The patient became alert gradually, but his amnestic syndrome remained unchanged. Vidarabine may be recommended in the treatment of HZV encephalitis when aciclovir is not effective.

Cytosolic calcium transients differ between porcine coronary arterial and aortic smooth muscle cells in primary culture.

Using quin 2 microfluorometry of porcine vascular smooth muscle cells in primary culture at 25 degrees C, we investigated differences in cytosolic calcium transients between epicardial coronary artery and aorta. Both in coronary arterial and aortic smooth muscle cells, histamine induced transient and dose-dependent elevations of cytosolic calcium concentrations, with a similar time course and EC50 (coronary artery, 1.4 x 10(-7) M; aorta, 1.8 x 10(7) M). However, a transient and dose-dependent elevation of cytosolic calcium concentrations was induced by norepinephrine in aortic smooth muscle cells (EC50 = 2.5 x 10(-7) M) but not in coronary arterial smooth muscle cells. Isoproterenol, which produced no change in cytosolic calcium concentrations in aortic vascular smooth muscle cells, significantly and dose dependently decreased concentrations of calcium in coronary arterial smooth muscle cells (EC50 = 1.5 x 10(7) M). Dibutyryl cAMP decreased the concentration of cytosolic calcium both in the coronary arterial and aortic vascular smooth muscle cells with a similar time course and EC50 (coronary artery, 9.8 x 10(-6) M; aorta, 1.1 x 10(-5) M). Intracellular concentration of cAMP was increased in response to isoproterenol, as determined with radioimmunoassay of the coronary arterial smooth muscle cells but not in the aortic cells. Thus, the characteristics of receptors on the sarcolemma may play a key role in the regulation of responsiveness of vascular smooth muscle cells to various vasoactive substances. Aortic smooth muscle cells are alpha-receptor dominant, and activation results in a transient elevation of cytosolic calcium concentrations. The epicardial coronary arterial smooth muscle cells are beta-receptor dominant, and activation results in an increase in cAMP and a reduction of cytosolic calcium concentrations. These results may account for the poor contraction, or relaxation, of epicardial coronary artery induced by sympathetic stimulation and exogenously applied catecholamines.

Characteristics of the histamine-sensitive calcium store in vascular smooth muscle. Comparison with norepinephrine- or caffeine-sensitive stores.

Using the microfluorometry of an intracellularly trapped calcium indicator dye, quin2, characteristics of intracellular Ca2+ store sites sensitive to histamine, norepinephrine, or caffeine were investigated using rat vascular smooth muscle cells in primary culture at 25 degrees C. With similar time courses, both histamine- and the norepinephrine-sensitive Ca2+ store sites were readily depleted in Ca2(+)-free medium and almost completely replenished by loading the cells with 1.0 mM Ca2+ solution for 3 min, while the caffeine-sensitive Ca2+ store site was little affected. In the absence of extracellular Ca2+, transient elevations of cytosolic Ca2+ repeatedly appeared in response to repetitive applications of histamine, norepinephrine, or caffeine, with progressive reductions in peak levels. Histamine released Ca2+ from the norepinephrine-sensitive store site and norepinephrine released Ca2+ from the histamine-sensitive one. On the other hand, caffeine had little effect on the histamine- and/or the norepinephrine-sensitive Ca2+ store site in Ca2(+)-free medium, and vice versa. We propose that the location and mechanisms of release of Ca2+ of the histamine-sensitive Ca2+ store site are identical with events at the norepinephrine-sensitive site, and differ from the caffeine-sensitive one, in vascular smooth muscle cells in primary culture.

Intracellular free calcium transients induced by norepinephrine in rat aortic smooth muscle cells in primary culture.

In cultured rat arterial smooth muscle cells treated with quin 2, cytosolic Ca2+ transients induced by norepinephrine were recorded microfluorometrically. In the presence or absence of extracellular Ca2+, norepinephrine induced transient and dose-dependent elevations in cytosolic Ca2+, with a similar time course, the peak levels being observed at 2 min. These transient elevations in cytosolic Ca2+ were dose-dependently inhibited by alpha-adrenergic antagonists, the order of potency being prazosin greater than phentolamine greater than yohimbine, irrespective of the presence of extracellular Ca2+. We propose that with or without extracellular Ca2+, norepinephrine activates mainly alpha-1 adrenoceptors leading to a release of Ca2+ from intracellular stores. This would explain the transient elevation in cytosolic Ca2+ in rat aortic vascular smooth muscle cells in primary culture.

Histamine activates H1-receptors to induce cytosolic free calcium transients in cultured vascular smooth muscle cells from rat aorta.

Using an intracellularly trapped dye, quin 2, the effects of histamine on cytosolic free calcium concentrations in rat aortic vascular smooth muscle cells in primary culture were recorded, microfluorometrically. When the cells were exposed to histamine, both in the presence and the absence of extracellular Ca2+, there was a rapid, transient and dose-dependent elevation of cytosolic Ca2+ concentrations, with a similar time course. This elevation of cytosolic Ca2+ was dose-dependently inhibited by mepyramine, but not by cimetidine. Thus, histamine activates H1- but not H2- receptors to mediate a release of Ca2+ from the store sites, and there is a rapid and transient elevation of cytosolic Ca2+.

Quin2 microfluorometry and effects of verapamil and diltiazem on calcium release from rat aorta smooth muscle cells in primary culture.

We investigated the effects of the Ca2+ antagonists diltiazem and verapamil on release of Ca2+ from intracellular store sites of rat aorta vascular smooth muscle cells in primary culture. Using the microfluorometry of Ca2+-indicator dye quin2, relative changes in cytosolic Ca2+ concentration could be measured. In the presence of 1 mM extracellular Ca2+, both diltiazem (IC50, 0.31 microM) and verapamil (IC50, 0.47 microM) dose-dependently inhibited elevations in the cytosolic Ca2+, as induced by depolarization of the plasma membrane with high extracellular K+. In the absence of extracellular Ca2+, caffeine and high extracellular K+ induced transient and dose-dependent elevations of the cytosolic Ca2+, and these elevations were not inhibited by either diltiazem or verapamil. Norepinephrine also induced a transient and dose-dependent elevation of cytosolic Ca2+ in the absence of extracellular Ca2+. However, this elevation was inhibited by verapamil and diltiazem (when the norepinephrine concentration was 10(-5) M, IC50 for verapamil and diltiazem was 4.0 and 24.9 microM, respectively). Thus, while verapamil and diltiazem may have no direct effect on the release of Ca2+ from the depolarization- and the caffeine-sensitive intracellular Ca2+ storage sites, the agents do seem to inhibit the adrenoceptor-mediated Ca2+ release mechanism in vascular smooth muscle cells.