Phosphoinositides and inositol phosphates in Discopyge tschudii electrocyte membranes |
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Institution: | 1. Sotio a.s, Prague, Czech Republic;2. Department of Immunology, 2nd Faculty of Medicine, Charles University, University Hospital Motol, Prague, Czech Republic |
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Abstract: | - 1.1. The metabolism of inositol (Ins)-containing phospholipids and inositol phosphates has been studied by following the incorporation and distribution of myo-3 H]Ins in metabolically active electrocytes from the electric ray Discopyge tschudii.
- 2.2. The apparent initial rate of myo-3H]Ins incorporation into total phosphoinositides was ca 8.2 fmol/mg protein/hr. Phosphatidylinositol (Ptdlns) displayed the highest levels of labelling. Lithium inhibited this incorporation probably by limiting the recycling of myo-3H]Ins from 3H]Ins-monophosphate.
- 3.3. The formation of water-soluble products of phosphoinositides between 7 and 24 hr was 4.1 ± 0.2, 0.4 ± 0.2 and 3.0 ± 1.0 fmol/μmmol total lipid phosphorus for myo-3H]InsP, -InsP2 and Ins-P3 respectively.
- 4.4. Lithium ions are shown to modulate phosphoinositide synthesis and Ins-phosphate accumulation. Ins-mono-, bis- and tris-phosphate production was enhanced 5-, 3- and 2-fold by Li +.
- 5.5. The above results suggest the participation of a C-type phospholipase and of Li-sensitive phosphatases in the modulation of phosphoinositide metabolism in the electrocyte.
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