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Biphasic modulation of choline uptake and phosphatidylcholine biosynthesis by vasopressin in rat cardiac myocytes
Author(s) -
Man Adrian S.,
Lee Edmund,
Choy Patrick C.
Publication year - 1994
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02537085
Subject(s) - vasopressin , phosphatidylcholine , phosphocholine , choline , biosynthesis , phospholipid , choline kinase , biochemistry , myocyte , biology , medicine , endocrinology , chemistry , enzyme , membrane
The effect of vasopressin on choline uptake and phosphatidylcholine biosynthesis in isolated rat heart myocytes was investigated. Myocytes were incubated with labelled choline in the presence of 0.05–1.0 μM vasopressin. Uptake of choline was enhanced (25%) by a low concentration (0.2 μM) of vasopressin, but was attenuated (19%) by a higher vasopressin concentration (1.0 μM). The biosynthesis of phosphatidylcholine was also affected by vasopressin in a biphasic manner. At low concentrations of vasopressin, a general increase in cytosine triphosphate:phosphocholine cytidylyltranferase activity was observed that caused an enhanced conversion of phosphocholine to phosphatidylcholine via the cytidine diphosphocholine pathway. At high vasopressin concentrations, a decrease in the activity of cytidylyltransferase was detected, which was caused by the translocation of the enzyme from the microsomal fraction to the cytosolic fraction. The decrease in enzyme activity coincides with a reduction in the conversion of labelled phosphocholine to phosphatidylcholine. In view of the fact that phospholipid biosynthesis in rat hepatocytes is inhibited by vasopressin at all concentrations, the biphasic modulation of phosphatidylcholine biosynthesis in rat heart myocytes illustrates the diverse effects of this hormone in different mammalian tissues.