Calcium independent contraction induced by iodoacetic acid in isolated cerebral arteries.

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Abstract
In helically-cut strips of cerebral arteries isolated from dogs and monkeys, the addition of 1 mM iodoacetic acid (IAA) produced contractions during an early period (5 to 10 min) and also a prolonged exposure (50 to 70 min). The early contraction was abolished by exposure to Ca++-free media containing EGTA, and significantly attenuated by treatment with procaine or dantrolene. Verapamil, lidocaine, ATP and pyruvate did not inhibit the contraction. On the other hand, the late contraction was not prevented by exposure to Ca++-free, EGTA-containing media and by treatment with procaine, dantrolene, lidocaine, ATP or pyruvate. Nitroglycerin and papaverine did not relax the IAA-contracted arteries. In dog and monkey mesenteric arteries and dog coronary, renal and femoral arteries, IAA elicited contractions after a prolonged exposure, which were not inhibited by soaking the preparations in Ca++-free, EGTA-containing media. Passive tensions developed by rapid stretch in Ca++-free media did not differ in IAA-treated and control arteries. During an early period of IAA actions, Ca++ appears to be released from intracellularly stored sites in the amount sufficient to produce significant contractions in cerebral, but not in peripheral arteries. It is concluded that the involvement of Ca++ in the late contraction induced by IAA is if any minimal, and such a contraction may be associated with functional alterations induced by the metabolic inhibitor in arterial tissues other than smooth muscle.