Tomoko Shimada

Extra- and intracellular calcium in vanadate-induced contraction of vascular smooth muscle.

SummaryThe effects of extracellular Ca and Ca antagonists on vanadate-induced contractions of vascular smooth muscles of aortae and mesenteric arteries from rabbits, guinea pigs, and Wistar-Kyoto (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) were studied. Vanadate-induced contractions of aortae were greatly diminished by extracellular Ca removal; the size of the remaining contraction was variable. Vanadate-induced contractions of mesenteric arteries, which were only observed in the presence of elevated K, were suppressed by the removal of Ca. Verapamil and nifedipine depressed vanadate-induced contractions of aortae from WKY and SHRSP, whereas they produced no or only slight inhibition of responses in guinea pig and rabbit aortae. Ca uptake into smooth muscle cell increased in the presence of vanadate, but the increase was much less than that induced by high K. In saponin-skinned smooth muscle, vanadate depressed the Ca-induced contraction. It is concluded that the vanadate-induced contraction utilizes both extracellular and intracellularly bound Ca, the relative contribution of which varies from preparation to preparation.

Relaxation of mesenteric artery of stroke prone spontaneously hypertensive rats by calcium removal.

1. The time courses of the relaxation, induced by removal of extracellular Ca2+, of K‐depolarized mesenteric artery preparations from stroke prone spontaneously hypertensive rats (SHRSP) and Wistar‐Kyoto rats (WKY) were compared.

Noradrenaline Content and Release in the Mesenteric Artery of Stroke-Prone Spontaneously Hypertensive Rats (SHRSP) and a New Strain of SHRSP (M-SHRSP)

Adrenergic innervation in the main trunk of the mesenteric artery was studied in stroke-prone spontaneously hypertensive rats (SHRSP) as well as in a new strain of SHRSP (M-SHRSP) and was compared with that of normotensive Wistar Kyoto rats (WKY). Noradrenaline (NA) content and high K-induced NA release in the artery of 6-week-old SHRSP and M-SHRSP were greater than those in the artery of WKY. These results suggest that a higher adrenergic innervation of the artery might be involved in the development of hypertension in SHRSP and M-SHRSP.

Effect of vanadate on cooling-induced tension changes in K-depolarized smooth muscles from guinea-pigs

Sodium vanadate reversed cooling‐induced relaxation of K‐depolarized taenia coli of guinea‐pigs but failed to reverse it in the portal vein and uterus. It potentiated cooling‐induced contraction of K‐depolarized vas deferens and ureter. These effects were not mediated by the inhibition of Na,K‐ATPase, but by the inhibition of the Ca‐pump.