Change in Ca2+ sensitivity of cerebrovascular smooth muscle in experimental chronic cerebral vasospasm.
The mechanism of chronic cerebral vasospasm was investigated by examining the relation between cytosolic Ca2+ level ([Ca2+]i) and muscle contraction in vascular smooth muscle after experimental vasospasm produced by the two-hemorrhage method in the canine basilar artery. [Ca2+]i and tension were recorded simultaneously with a fluorimeter using the arterial strips with a Ca2+ indicator, fura-2. High K+ concentration (72.4 mM) and U-46619 (thromboxane A2 analogue, 10(-8) M) were used as stimulants. The increase in contractile tension per [Ca2+]i per unit cross-sectional area was calculated, and compared for the vasospasm and the control groups. The increase in [Ca2+]i in the vasospasm group was smaller than that in the control group, so the increase in tension per [Ca2+]i per unit sectional area was larger in the vasospasm group. This value was much larger for the contraction induced by U-46619 than that induced by high K+ concentration in both groups. These results suggest that there is an increase in the basal Ca2+ sensitivity of the contractile elements in vasospastic vessels. In addition, the U-46619-induced increase in Ca2+ sensitivity seemed to be augmented in the vasospasm group.
Tanaka
Y
Y
Department of Surgical Neurology, Jichi Medical School, Tochigi, Japan.
Masuzawa
T
T
Saito
M
M
Yamada
T
T
Fujimoto
K
K
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000473:pathology / Q000503:physiopathology*; D001488:Basilar Artery / Q000473:pathology / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D002546:Ischemic Attack, Transient / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology*; D011188:Potassium / Q000378:metabolism; D014661:Vasoconstriction / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D011188:Potassium; D002118:Calcium