ACTINOMYCIN D INHIBITION OF MICROSOMAL-BOUND HYDROXYPROLINE FORMATION IN RABBIT EMBRYO SKIN IN VITRO

Abstract
The biosynthesis of collagen has been studied in vitro using rabbit embryo skin. Time course studies of proline incorporation into the microsomal fraction indicated a significant uptake into protein-bound proline and into collagen hydroxyproline. Maximally, proline was incorporated in the ratio of 101 of that of hydroxyproline. Uridine-2-C14 was used to measure RNA synthesis, and actinomycin D was the inhibitor utilized to block nuclear RNA formation. The data suggest that actinomycin D inhibition of RNA synthesis also blocked the formation of microsomal-bound hydroxyproline. Hence, the inactivity of the system following the treatment with actinomycin D suggests that collagen messenger RNA is extremely unstable.