Dissociation of phosphorylase a activation and contractile activity in rat portal vein
- 1 May 1984
- journal article
- research article
- Published by Wiley in Acta Physiologica Scandinavica
- Vol. 121 (1), 23-30
- https://doi.org/10.1111/j.1748-1716.1984.tb10453.x
Abstract
Isometric force, glycogen phosphorylase activity and lactate production were measured under conditions known to alter intracellular Ca2+ and cAMP to assess the role of these messengers in the coordination of metabolism with contractility in rat portal vein. Total phosphorylase (a+b) activity, was independent of treatment. The activity ratio phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on or high‐K+ medium, and 0.57 after 20 min treatment with 10–5 M isoproterenol+10‐4 M papaverine. Under both of these conditions the muscle was totally relaxed. The phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on extracellular Ca2+, both in normal and depolarizing medium. This suggests a lower Ca2+ sensitivity of the contractile than the phosphorylase system under these conditions, known to be associated with raised intracellular cAMP. During spontaneous activity and high‐K+ induced contractures phosphorylase activity was increased compared to the relaxed state in Ca2+‐free medium. A high level of phosphorylase activity (0.48) was elicited by the addition of 300 mM sucrose, which induces a contracture in Ca2+‐free medium. Lactate production was in general parallel to phosphorylase activity, except for a relative increase in anoxia. The results suggest that in the intact cell the Ca2+‐mediated linkage of contraction and phosphorylase may be modified by cAMP changing the Ca2+ sensitivities of the two systems in opposite directions.Keywords
This publication has 35 references indexed in Scilit:
- Influence of Anoxia and Dinitrophenol on the Phosphorylase a Activity and the Cyclic Nucleotide Content of Smooth MuscleActa Pharmacologica et Toxicologica, 1983
- Force-velocity relation in chemically skinned rat portal veinPflügers Archiv - European Journal of Physiology, 1983
- Regulation of Smooth Muscle ActomyosinAnnual Review of Physiology, 1981
- CALCIUM CONTROL OF MUSCLE PHOSPHORYLASE KINASE THROUGH THE COMBINED ACTION OF CALMODULIN AND TROPONIN*Annals of the New York Academy of Sciences, 1980
- Contraction of the rat portal vein in hypertonic and isotonic medium: rates of metabolismActa Physiologica Scandinavica, 1980
- Regulation and Kinetics of the Actin-Myosin-ATP InteractionAnnual Review of Biochemistry, 1980
- EFFECTS OF HYDRALAZINE AND VERAPAMIL ON PHOSPHORYLASE ACTIVITY AND GUANOSINE CYCLIC 3′,5′‐MONOPHOSPHATE LEVELS IN GUINEA‐PIG TAENIA COLIBritish Journal of Pharmacology, 1980
- Role of calcium and cyclic adenosine 3′:5′ monophosphate in regulating smooth muscle contraction: Mechanisms of excitation-contraction coupling in smooth muscleThe American Journal of Cardiology, 1979
- Oxygen Consumption and Lactate Production of the Rat Portal Vein in Relation to its Contractile ActivityActa Physiologica Scandinavica, 1977
- Contraction in Venous Smooth Muscle Induced by Hypertonicity. Calcium Dependence and Mechanical CharacteristicsActa Physiologica Scandinavica, 1974