The effect of hypoxia on the phosphorylation of contractile and other proteins in perfused rat heart challenged by isoprenaline.
Rat hearts perfused with 32Pi were made hypoxic by perfusion with medium gassed with N2/CO2 (19:1). There was a rapid decrease in tension development (25% of control within 40 s), but little change in the frequency of contraction, time to peak tension, or rate of relaxation. The phosphorylation of troponin-I, C-protein and myosin P-light chain was unaffected by 5 min of hypoxia, whereas the proportions of glycogen phosphorylase and pyruvate dehydrogenase in the active form increased slowly. When aerobically perfused hearts were challenged with a bolus (70 pmole) of D,L-isoprenaline, there was a large increase in contractile force, cyclic AMP concentration, phosphorylation of troponin-I and C-protein and activation of phosphorylase and pyruvate dehydrogenase. Hypoxia for 5 min caused a slight, progressive decrease in the response to isoprenaline of force, cyclic AMP and activation of phosphorylase and pyruvate dehydrogenase. In contrast, there was a larger decrease in the phosphorylation of troponin-I and C-protein, suggesting that the activity of cyclic AMP-dependent protein kinase towards the contractile proteins may be impaired by hypoxia. The phosphorylation of myosin P-light chain was unaltered by any condition. The response to hypoxia is compared to that of ischaemia, where a complete loss of the response to isoprenaline occurs after 5 min.
England
P J
PJ
Department of Cellular Pharmacology, Smith, Kline & French Research LTD., Herts, U.K.
Krause
E G
EG
D000818:Animals; D002118:Calcium / Q000502:physiology; D002395:Catecholamines / Q000494:pharmacology; D003285:Contractile Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D006321:Heart / Q000187:drug effects*; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology; D006005:Phosphorylases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D002395:Catecholamines; D003285:Contractile Proteins; D011768:Pyruvate Dehydrogenase Complex; D000242:Cyclic AMP; D006005:Phosphorylases; D011494:Protein Kinases; D007545:Isoproterenol; D002118:Calcium