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  • Title: Changes in cytosolic Ca2+ measured by use of fura-2 and contraction produced by quick stretch and various stimulants in canine cerebral artery.
    Author: Tanaka Y, Nakayama K, Shigenobu K.
    Journal: Res Commun Mol Pathol Pharmacol; 1998 Oct; 102(1):79-92. PubMed ID: 9920348.
    Abstract:
    Mechanical stimulation such as stretch generates myogenic contraction in cerebral arteries. Myogenic contraction of cerebral arteries in response to quick stretch is greatly modified by promoters and inhibitors of Ca2+ handling mechanisms including Ca2+ channel blockers. In the present study, in order to improve our understanding of the role of Ca2+ in the generation of stretch-induced contraction, changes in cytosolic free Ca2+ concentrations ([Ca2+]cyt) and contraction of canine cerebral artery in response to quick stretch were simultaneously measured by use of fura-2. The [Ca2+]cyt-tension relationship in the stretch-induced contraction was compared with those by various stimulants. Quick stretch at a rate of 10 cm/sec with the amount of 40% of the initial muscle length (=100%) produced a myogenic contraction in canine cerebral artery. The arterial [Ca2+]cyt enormously increased after the stretch, which preceded the occurrence of the delayed contraction in response to stretch. [Ca2+]cyt-tension relationships in the stretch-induced contraction changed counterclockwise as those in the contractions induced by high KC1 and pharmacological agonistic stimulants such as 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1). The contraction in response to quick stretch at the maintenance phase was far smaller than those produced by high KC1 or agonistic stimulants at the same changes in [Ca2+]cyt. These findings suggest that in the cerebral artery contraction in response to quick stretch, elevated cytosolic Ca2+ is utilized less efficiently as compared with the contractions elicited by other stimulants. The apparent low Ca2+ sensitivity of stretch-induced contraction in dog cerebral artery might be related to the low efficiency of cytosolic Ca2+ elevated by the Ca2+ release from intracellular storage sites upon stretch.
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