On two paradoxical side-effects of prednisolone in rats, ribosomal RNA biosyntheses, and a mechanism of action.

Liver enlargement and muscle wastage occurred in Wistar rats following the subcutaneous administration of prednisolone. In the liver both the content of RNA and the biosynthesis of ribosomal RNA increased while both the RNA content and ribosomal RNA biosynthesis were reduced in the gastrocnemius muscle. It is suggested that the drug acted in a selective and tissue-specific manner to enhance ribosomal RNA synthesis in the liver and depress such synthesis in the muscle. This view supports the contention that the liver and muscle are independent sites of prednisolone action.