The isolation of adult rat cardiomyocytes activates inositol(1,4,5) trisphosphate 3'kinase activity.
Addition of norepinephrine to [3H]inositol-labeled rat hearts or isolated left atria caused the release of inositol(1,4,5)trisphosphate which was metabolized by dephosphorylation to inositol(4)monophosphate. Products of the inositol(1,4,5)trisphosphate 3'-kinase pathway were not present at detectable levels. When norepinephrine was added to [3H]inositol-labeled isolated adult cardiomyocytes the released inositol(1,4,5)trisphosphate was metabolized partially by phosphorylation as evidenced by the presence of the immediate phosphorylation product inositol(1,3,4,5)-tetrakis-phosphate and its dephosphorylation products inositol (1,3,4)trisphosphate and inositol(1,3)-bisphosphate. Direct measurement of inositol trisphosphate 3'-kinase activity in cytosols prepared from intact hearts and isolated myocytes demonstrated activation of the enzyme during cell isolation from 20 +/- 0.5 p mol/min/mg protein to 124 +/- 14 (mean +/- S.E.M., n = 3, P < 0.001). These data show that the kinase pathway is suppressed in healthy heart tissue and show that it can be activated under conditions such as those required for cell isolation.
Woodcock
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EA
Cellular Biochemistry Laboratory, Baker Medical Research Institute, Prahran, Australia.
Schoenwalder
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Anderson
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D000818:Animals; D002469:Cell Separation; D004790:Enzyme Induction; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D007536:Isomerism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D007295:Inositol Phosphates; D007770:L-Lactate Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase