Stimulation of hepatic RNA synthesis in dwarf mice by ovine prolactin

Abstract

Dwarf mice ( dw dw ) have a lower liver RNA to DNA ratio compared to their congenic littermates (+/?). Injection of ovine prolactin into dwarf mice increases the total RNA content of liver. Dwarf mice appear to incorporate less [ 3H]uridine into total hepatic RNA after pulse injection than normal mice. Prolactin first stimulates the synthesis of guanine-rich then uridine-rich RNA of the whole liver homogenate. In liver nuclei, incorporation of [ 14C]guanine into RNA after correction for the acid-soluble pool is significantly increased during the first 3 days of treatment, whereas [ 3H]uridine incorporation rises substantially only after 4–5 days of treatment. In mitochondria, which incorporate labeled precursors into RNA, prolactin stimulates mainly the synthesis of uridine-rich RNA. A single dose of prolactin ( 10 I.U. 7 g body weight) stimulates the assembly of ribosomes into polyribosomes. Total amounts of ribosomes and polyribosomes continuously increase during the 5 days of prolactin treatment.