Premium
Does the inositol tris/tetrakisphosphate pathway exist in rat heart?
Author(s) -
Renard D.,
Poggioli J.
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)81254-1
Subject(s) - inositol , tris , inositol phosphate , chemistry , medicine , endocrinology , enzyme , inositol trisphosphate , biochemistry , biology , receptor
Appearance of two isomers of inositol trisphosphate (InsP 3 ) was observed when [ 3 H]inositol prelabelled rat heart ventricles were stimulated for 10 and 30 s with noradrenaline. In contrast, inositol tetrakisphosphate (InsP 4 ) could not be detected. However the existence of the inositol tris/tetrakisphosphate pathway was demonstrated by studying [ 3 H]inositol 1,4,5‐trisphosphate (Ins‐1,4,5‐P 3 ) metabolism in a soluble fraction of rat heart. There, [ 3 H]Ins‐1,4,5‐P 3 was phosphorylated to form [ 3 H]Ins‐1,3,4,5‐P 4 . Raising [Ca 2+ ] from 1 nM to 1, μM increased InsP 3 kinase activity by 2‐fold (EC 50 for Ca 2+ 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.