Phosphoinositides and inositol phosphates in Discopyge tschudii electrocyte membranes

ARIAS H; BARRANTES FJ

INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND CELLULAR BIOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1990 vol. 22 p. 1387 - 1392

1357-2725

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. 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. 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/ìmmol total lipid phosphorus for myo-[3H]InsP, -InsP2 and Ins-P3 respectively.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. 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.