Coordinate Accumulation of the MRNAs for the Alpha, Beta, and Gamma Chains of Rat Fibrinogen Following Defibrination

Cell-free translation and hybridization to cloned cDNA probes were used to study variations in fibrinogen mRNA levels in the livers of rats injected with Malayan pit viper venom and glucocorticoids. Animals defibrinated with Malayan pit viper venom showed a rapid and substantial increase in the relative abundance of hepatic mRNAs for the A alpha, B beta, and gamma chains of fibrinogen. The onset, rate, and maximal extent of message accumulation were virtually identical for each of the three fibrinogen polypeptide chains. This response was detectable 1-2 h after injection of venom and, by 12-16 h, fibrinogen species made up approximately 10% of the polyadenylated RNA compared to less than 1% in noninjected animals. Physiologic levels of glucocorticoids appeared to be necessary for maximal levels of message; adrenalectomized animals had a median 4.8-fold increase in fibrinogen mRNA species after defibrination compared with a 12.5-fold increase in normal animals. Although it is uncertain whether the changes in mRNA levels are a function of increased transcription or message stabilization, the similar kinetics of accumulation suggest that a common mechanism is responsible for coordinating the levels of each fibrinogen mRNA.