Phosphatidic acid and polyphosphoinositide formation in a broken cell preparation from rat brain : effects of different incubation conditions

Abstract--The effect of age on phosphate incorporation i to phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidic a id (PA) was studied. Lysed crude synap-tosomal fractions of different brain regions of 3-month-old and 32-month-old Brown Norway rats were used. The brain regions tested were the hippocampus, frontal cortex, occipital/parietal cortex, entorhinal/pyriformal cortex, striatum/septum, thalamus and hypothalamus. The individual specific phos-phorylating activities were unevenly distributed within the brain of Brown Norway rats. Strikingly, the distribution of phosphate incorporation i to PIP2 was opposite from that of phosphate incorporation i to PA. Phosphate incorporation i to PA decreased (-15%) with age in almost all brain regions tested, whereas phosphate incorporation i to PIP2 decreased with age only in the frontal cortex (-20%) and in the hypothalamus (-8%). The effects of age may reflect a deterioration f phosphoinositide m tabolism, with its function in signal transduction coupled to receptors via G-proteins, in the brain regions involved. In addition, there was an age related ecrease in protein content and total phospholipid phosphorus content of lysed crude synaptosomal preparations of all brain regions. The high correlation between the changes in these parameters may be indicative of a decrease in the number or size of synaptosomes with age in the brain regions involved