Does the inositol tris/tetrakisphosphate pathway exist in rat heart?
- 8 June 1987
- journal article
- Published by Wiley in FEBS Letters
- Vol. 217 (1) , 117-123
- https://doi.org/10.1016/0014-5793(87)81254-1
Abstract
Appearance of two isomers of inositol trisphosphate (InsP3) was observed when [3H]inositol prelabelled rat heart ventricles were stimulated for 10 and 30 s with noradrenaline. In contrast, inositol tetrakisphosphate (InsP4) could not be detected. However the existence of the inositol tris/tetrakisphosphate pathway was demonstrated by studying [3H]inositol 1,4,5‐trisphosphate (Ins‐1,4,5‐P3) metabolism in a soluble fraction of rat heart. There, [3H]Ins‐1,4,5‐P3 was phosphorylated to form [3H]Ins‐1,3,4,5‐P4. Raising [Ca2+] from 1 nM to 1, μM increased InsP3 kinase activity by 2‐fold (EC50 for Ca2+ approx. 56 nM). This effect appeared to be due to an increase of the apparent V max of the enzyme while the apparent K m was unchanged.Keywords
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