ACCUMULATION OF 3H-1-LYSINE BY BRAIN AND PLASMA IN MALE AND FEMALE RATS TREATED ACUTELY WITH MORPHINE SULFATE

Adult male and female Wistar rats were injected with a single dose of 40 mg/kg of morphine sulfate via indwelling intrajugular cannulas and killed two hours later. ³H-1-lysine was injected at various time intervals before the death of the animals. The distribution of the labelled amino acid was then determined in the free amino acid and lipid-nucleoprotein-extracted protein fractions of plasma and cerebral grey matter. The accumulation of ³H-activity was also determined in various areas of the brain, dorsal root ganglia, pectoral muscle and liver. Morphine-treatment produced an elevation of free ³H-lysine levels in plasma and cerebral grey matter and a decrease in incorporation into protein. A significant sex difference was noted, such that in control males the plasma free ³H-lysine and protein fractions were higher than in females. In the morphine-treated group the values obtained from males were lower than for females. In cerebral grey matter, the free ³H-lysine was significantly lower in control and morphine-treated males than in females. In the protein fraction, such sex differences varied with the time elapsed after injection of amino acid and did not clearly favor either sex. The accumulation of ³H-activity in tissue blocks taken from various regions of CNS was unaffected by morphine-treatment in subcortical components. The values were generally higher in females. ³H-accumulation was significantly altered in cortical components in the male group. In cerebral white matter, the morphine-treated males showed significant elevations of accumulation. Females showed an elevation of ³H-accumulation in the morphine-treated group only when the data was subjected to a group comparison. In the peripheral nervous system, ³H-accumulation was significantly depressed by morphine-treatment only in males. The female values were again significantly higher than those from the males. The male liver demonstrated a significant depression in accumulation of ³H-activity in the morphine-treated group. Liver tissue from females was less responsive and had higher uptakes than in males. Skeletal muscle showed no alteration in ³H-accumulation after morphine treatment in either sex.