Hydrolysis of Adenosinetriphosphate and Creatinephosphate on Isometric Contraction of Vascular Smooth Muscle

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Abstract
Beviz, A., L. Lundholm, E. Xiohme‐Lundholrn and N. Vanios. Hydrolysis of adenosinetriphosphate and creatinephosphate on isomdric contraction of vasculur smooth muscle. Actaphysioi. scand. 1965. 65. 268–272. In experiments on isolated bovine mesenteric artery the adenosinetriphosphate (ATP) and creatinephosphate (CrP) contents were determined after isometric contraction by adrenaline. 1 min after addition of adrenaline (1.10‐6) when the rise of tension was one‐half maximum, the ATP content had fallen by 0.16 ± 0.07 μmoie/g of tissue and the CrP content by 0.22 ± 0.07 μmole. At the end of 7 min, when the elevation of tension was maximal, hydrolysis of ATP amounted to 0.37 ± 0.10 μmiole and that of CrP to 0.40 ± 0.09 μmole/g of tissue. There was no definite change of the adenosinediphosphate (ADP) or adenosinemonophosphate (AMP) content. When adrenaline had exerted its action for 60 min and the tension was still at maximal level: the ATP content did not differ from that in the controls, whereas the CrP content was still reduced by 0.52 ± 0.18μmolelg of tissue. Calculation of the P.L/H quotient from the summed hydrolysis of ATP and CrP and the rise in tension during the first minute of contraction, gave a value of 9.5. This value was of similar magnitude to that found on thermoelectric determination of the heat production associated with isometric contraction of striated and smooth muscle.