摘要:

A plasma membrane-enriched fraction of vesicles from rat mesenteric artery possessed ATP-dependent calcium properties similar to those which have been reported previously. The catalytic subunit from a soluble, cyclic AMP-dependent protein kinase was prepared from the same tissue, in partially purified form. Calcium uptake by membrane vesicles increased 30% in the presence of this kinase. This effect was proportional to the kinase concentration, and was blocked by either catalytic subunit inhibitor or by prior boiling of the subunit preparation. Stimulation of calcium uptake by the kinase occurred maximally between 1 and 10 µMfree calcium. These findings suggest that cyclic AMP and its dependent protein kinase may participate in the regulation of smooth muscle tension at high free myoplasmic calcium concentrations

ISSN:1018-1172    

DOI:10.1159/000158528

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Single smooth muscle cells from bovine coronary artery were obtained by enzymatic digestion. 20.1 ± 3.2% (mean value of seven experiments) of the dispersed cells were in a relaxed, noncontracted state. These cells responded to electrically induced depolarization with a graded contraction to a maximum shortening of 47.8% of initial length; the corresponding maximum for K+-induced depolarization was 61.7% of initial length. Cells relaxed only a small percentage (≈ 20%) of the amount of shortening, but could be restimulated several times to contract to even shorter lengths. The decrease in mean cell length of dispersed cells exposed to serotonin, acetylcholine, and ergonovine maleate was 21.0, 23.0 and 25.5%, respectively (p < 0.05). No significant decrease in cell length was obtained with norepinephrine. The ultrastructure of the relaxed cells seemed to be unaltered, suggesting that the accuracy of the physiological results is not impaired by induced structural dama

ISSN:1018-1172    

DOI:10.1159/000158529

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

We have measured the relaxation of rat mesenteric small arteries (internal diameter ca. 200 µm) from a potassium contracture under conditions where the transplasmalemmal sodium gradient was altered. Adjustment of the sodium gradient was made either by exposing vessels to ouabain (1 mM) for different periods to vary the intracellular sodium concentration (Nai), or by varying the sodium concentrations of the relaxation solutions (Nao). Under normal conditions (where we have previously shown Nai is about 19 mM), vessels relaxed completely within 1 min in low sodium solutions (Nao = 25 mM) using either sucrose, choline-Cl or MgCl2 as substitutes. However, the relaxation (measured after 1 min) was reduced when sucrose substitution was used, and further experiments were made using this substitute. Here it was found that exposing vessels to ouabain, for example 90 min (thus increasing Nai to about 73 mM) and then performing the relaxation in a low sodium solution gave only about 50% relaxation after 1 min. Experiments with intermediate sodium concentrations in the relaxation medium showed that reduction to 100 mM had no significant effect on the relaxation, and that it was only below 50 mM that effects were most marked. The effects of altered sodium gradient were eliminated if the calcium concentration of the relaxation medium was zero. The results indicate that under normal physiological conditions, small changes in sodium gradient have little effect on calcium metabolism of rat mesenteric small arteries, but also that under extreme conditions net calcium extrusion does appear to be reduced by a reduced sodium gradient

ISSN:1018-1172    

DOI:10.1159/000158530

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Cells of human aorta were isolated by dispersing the tissue with collagenase and elastase. The isolated cells were stained in suspension by the acridine orange fluorescent stain. The intensity of red fluorescence (>580 nm) corresponding to the RNA content was measured in each individual cell and registered in a FACS II flow cytofluorometer. It was established that a cell population of human aorta is heterogenous with respect to RNA content. In a population of isolated cells, one can distinguish two subpopulations: (A) small cells with low RNA content, and (B) large cells with high RNA content. The ratio of both cell types varies in intima and media, and different types of atherosclerotic lesions. The share of cells belonging to subpopulation A is lower in media compared to intima. In intima, the number of these cells grows with the degree of atherosclerotic lesion. Possible reasons for the discovered metabolic heterogeneity of human aortic cells and prospects for the application of flow cytofluorometry to a research into cellular mechanisms of atherosclerosis is discussed.

ISSN:1018-1172    

DOI:10.1159/000158531

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

SGB (10-7–10–5M), a new piperazinyl antihypertensive agent, like prazosin (10–8_10–6M), a potent preferential α1-adrenoceptor antagonist, inhibited the contractile response of rabbit aorta to norepinephrine and methoxamine in a competitive manner whereas in the cat coronary and rabbit basilar artery, the inhibition by SGB was not a competitive one. The potency of the inhibitory action of SGB was less than that of prazosin in all preparations used. Neither SGB nor prazosin had any inhibitory effect on the response to potassium, 5-hydroxytryptamine, prostaglandin F2α, and excess Ca2+ in all preparations. In the rabbit aortic membrane preparation, the specific binding of [3H]-prazosin was inhibited, concentration-dependently, by SGB with IC50 value of 1.4 ± 0.09 µM. These studies indicated that SGB has an α1-adrenoceptor-blocking action though its potency is weaker t

ISSN:1018-1172    

DOI:10.1159/000158532

出版商:S. Karger AG    

年代:1984

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158533

出版商:S. Karger AG    

年代:1984

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158534

出版商:S. Karger AG    

年代:1984

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158527

出版商:S. Karger AG    

年代:1984

数据来源: Karger