Protein synthesis in pulmonary arteries from rats exposed to hyperoxia

These studies were undertaken to determine the relationship of early changes in the synthesis rates and contents of collagen, elastin, and soluble tissue protein of pulmonary arteries in rats exposed chronically to normobaric hyperoxia. The growth response of pulmonary arteries was characterized by proportionate increases in the contents of the three protein fractions after 7 days (130% of control) and 21 days (194% of control) of exposure. Fractional rates of protein synthesis were assessed both in vivo and in vitro with the use of several radiolabeled amino acids as tracers to minimize uncertainties of the relationships of the specific radioactivities of measured amino acid pools and the precursors for the proteins fractions. Values for fractional synthesis rates of collagen, elastin, and soluble protein in vitro in pulmonary arteries isolated from control rats were 2.2, 1.6, and 19%/day, respectively. Rates of synthesis of collagen and soluble protein in vitro were approximately 20% lower than that determined in control rats in vivo. The fractional synthesis rates of the three protein fractions in isolated arteries from experimental rats were unchanged after 1 day of hyperoxic exposure, decreased marginally after 3 days, and markedly increased after 7 days. At this time the absolute increments in the fractional synthesis rates of collagen (+4.7%/day) and elastin (+5.0%/day) were less than that of soluble tissue protein (+16%/day) and were more comparable to the accumulation rate of proteins in the tissue. The disproportionate increment in the fractional rate of soluble protein synthesis suggests that the fractional rate of degradation of soluble protein was also increased during the growth response in this model of hypertension.