Morphine and the incorporation of 32orthophosphate in vivo into phospholipids of the guinea pig cerebral cortex, liver and subcellular fractions

Abstract

This investigation was initiated to ascertain whether morphine in vivo would alter the incorporation of 32orthophosphate into phospholipids of guinea pig cerebral cortex, liver and subcellular organelles of these tissues. Morphine stimulated the incorporation of 32orthophosphate into whole cerebral cortex phospholipids 119 per cent at 16 hr and 87 per cent at 24 hr after 32orthophosphate as determined by total radioactivity measurements. A significant stimulation of the incorporation of 32orthophosphate ranging from 41 to 207 per cent occurred at 16 and 24 hr with individual phospholipids. No statistically significant effect was observed with total radioactivity data obtained from whole liver, although significance was observed with phosphatidylinositol and phosphatidic acid at later time intervals. A predominantly stimulatory effect on phospholipid metabolism was obtained with total radioactivity determinations on the subcellular fractions of the cerebral cortex. The major stimulatory effect occurred with the individual phospholipids at 48 hr in the soluble supernatant fraction (248–403 per cent). Total radioactivity studies with liver subcellular fractions provided a statistically significant effect at 48 hr (79–134 per cent). The effect on individual phospholipids from liver subcellular fractions was similar to the total radioactivity data. Morphine had both an inhibitory and stimulatory effect on the total radioactivity determinations of mitochondrial subfractions from the cerebral cortex at 16, 24 and 48 hr. A similar effect was observed with mitochondrial fractions subjected to osmotic shock. Total radioactivity determinations on phospholipids from microsomal subcellular fractions of liver were both stimu- latory and inhibitory at the various time intervals. A statistically significant stimulatory effect was observed with individual phospholipids at 48 hr from the smooth and rough microsomal liver subcellular fractions. It is concluded that morphine alters phospholipid metabolism in vivo and thus may directly affect cellular function in liver and neuronal activity in the central nervous system.