TY - JOUR
T1 - Calcium-dependent turnover of brain polyphosphoinositides in vitro after prelabelling in vivo
AU - Jolles, J.
AU - Schrama, L.H.
AU - Gispen, W.H.
PY - 1981/1/1
Y1 - 1981/1/1
N2 - Rat brain phospholipids were labelled in vivo by an intraventricular injection of 32P. The radioactivity was found to accumulate predominantly in limbic structures, particularly hippocampus and diencephalon. A rapid and high specific labelling of the inositol phospholipids and phosphatidic acid was observed. The rate of incorporation into a crude myelin fraction was similar to that into a mitochondrial/synaptosomal fraction although phosphatidylmyo-inositol 4, 5-diphosphate was especially enriched in myelin. Upon incubation in vitro of the brain fractions after 2 h prelabelling in vivo, both phosphatidylvnyo-inositol 4-phosphate and phosphatidyl-myo-inositol 4, 5-diphosphate rapidly lost their radioactivity. Half of the labile fraction of the incorporated 32P was removed within 2 min. None of the other phospholipids changed in the 30 min in vitro incubation period. The metabolism of the polyphosphoinositide proceeded at a lower rate when the temperature was lowered, and was Ca2+-dependent. Further subcellular fractionation revealed that purified synaptosomes and myelin contained highly labelled phosphatidyl-myo-inositol 4, 5-diphosphate. Mitochondria contained highly labelled phosphatidyl-myo-inositol but no phosphatidyl-myo-inositol 4-phosphate or phosphatidyl-myo-inositol 4, 5-diphosphate. ACTUH1–24 did not inhibit the in vitro dephosphorylation of prelabelled polyphosphoinositide, confirming previous findings that the peptide affects the polyphosphoinositide kinases and not the respective phosphatases.
AB - Rat brain phospholipids were labelled in vivo by an intraventricular injection of 32P. The radioactivity was found to accumulate predominantly in limbic structures, particularly hippocampus and diencephalon. A rapid and high specific labelling of the inositol phospholipids and phosphatidic acid was observed. The rate of incorporation into a crude myelin fraction was similar to that into a mitochondrial/synaptosomal fraction although phosphatidylmyo-inositol 4, 5-diphosphate was especially enriched in myelin. Upon incubation in vitro of the brain fractions after 2 h prelabelling in vivo, both phosphatidylvnyo-inositol 4-phosphate and phosphatidyl-myo-inositol 4, 5-diphosphate rapidly lost their radioactivity. Half of the labile fraction of the incorporated 32P was removed within 2 min. None of the other phospholipids changed in the 30 min in vitro incubation period. The metabolism of the polyphosphoinositide proceeded at a lower rate when the temperature was lowered, and was Ca2+-dependent. Further subcellular fractionation revealed that purified synaptosomes and myelin contained highly labelled phosphatidyl-myo-inositol 4, 5-diphosphate. Mitochondria contained highly labelled phosphatidyl-myo-inositol but no phosphatidyl-myo-inositol 4-phosphate or phosphatidyl-myo-inositol 4, 5-diphosphate. ACTUH1–24 did not inhibit the in vitro dephosphorylation of prelabelled polyphosphoinositide, confirming previous findings that the peptide affects the polyphosphoinositide kinases and not the respective phosphatases.
U2 - 10.1016/0005-2760(81)90094-1
DO - 10.1016/0005-2760(81)90094-1
M3 - Article
SN - 0005-2760
VL - 666
SP - 90
EP - 98
JO - BBA - Lipids and Lipid Metabolism
JF - BBA - Lipids and Lipid Metabolism
IS - 1
ER -