Inhibitory effects of chronic administration of morphine on uridine and thymidine incorporating abilities of mouse liver and brain subcellular fractions

Attempts have been made to examine the in vitro and in vivo effects of morphine sulfate on the incorporation of ¹⁴C-labeled uridine and thymidine into acid-insoluble fractions of mouse liver and brain. Morphine, in vitro or after administration in vivo, produced no significant changes in the uridine and thymidine incorporating abilities of liver and brain homogenates. The chronic administration of morphine produced dose-dependent decreases in uridine and thymidine incorporating abilities of liver and brain homogenates and of their subcellular fractions such as nuclei, mitochondria and microsomes.