Electron-microscopic studies on reaggregate cultures of vascular smooth muscle cells from normotensive and spontaneously hypertensive rats

Angiotensin stimulates Ca2(+)-dependent action potentials in cultured smooth muscle cells

The steady-state angiotensin II response was measured in primary cultures of reaggregated vascular smooth muscle cells derived from rat aorta by use of intracellular microelectrode recording of membrane potentials. Angiotensin II (10(-9)-10(-6) M) produced a depolarization which triggered a single action potential, consisting of a spike plus plateau. In addition, angiotensin II prolonged the action potential plateau and lowered input resistance. The angiotensin II-induced action potentials and the action potential plateau prolongation were inhibited by verapamil. Saralasin blocked the occurrence of angiotensin II-induced action potentials and reversed the increase in action potential duration provoked by angiotensin II. Saralasin, in the absence of angiotensin II, exhibited agonistic activity which was manifest by plateau prolongation. Therefore, angiotensin II, through interaction of the peptide with its receptor, depolarizes cultured vascular smooth muscle cells and prolongs the calcium-dependent action potentials. These effects could be mediated by the known ability of angiotensin II to stimulate production of inositol trisphosphate and diacylglycerol, and activation of protein kinase C.

Characterization of a coronary vasoconstrictor produced by cultured endothelial cells

The vasoactive effects of media obtained from bovine aortic endothelial cells (EC) in culture were directly tested on isolated rings of the porcine left anterior descending coronary artery. Increasing concentrations of EC-conditioned culture media resulted in progressive dose-dependent increments in isometric tension in porcine, bovine, and canine coronary arteries; the response did not require an intact endothelium. Control (nonconditioned) media and that conditioned by fibroblasts or vascular smooth muscle cells in culture had negligible effects on vessel tone. The vasoconstriction required extracellular Ca2+ and was unaffected by inhibitors of cyclooxygenase and lipoxygenase or by antagonists to the alpha- or beta-adrenergic, serotonergic, histaminergic, or cholinergic receptor systems. Calibrated gel filtration of the media indicated a molecular weight of 8,500 for the vasoactive factor; treatment of the EC-conditioned media with either sodium dodecyl sulfate, trypsin, alkali, or with acid hydrolysis completely abolished the vasoconstrictive effect. These findings and others now provide evidence for the existence of an EC-derived polypeptide vasoconstrictor that may be important in the regulation of vascular smooth muscle contractility.

Cerebrovascular muscle cultures. I. Isolation, growth and morphological characterization

This study describes the development and establishment of pure cerebrovascular smooth muscle cells derived from dissociated cells of microvessels obtained from brains of rats. The cultured and propagated vascular smooth muscle cells display histochemical and ultrastructural characteristics of smooth muscle cells consistent with those reported in cultures of peripheral vessels. Thus, the cerebrovascular smooth muscle cultures provide a new model system for the investigation of their function, particularly in relation to the regulation of cerebral blood flow and blood pressure.