Effect of cigarette smoke on protein synthesis in brain and liver

Abstract

The rates of protein synthesis in brain and liver were determined in 2 inbred mouse strains (BALB/c and CXBH) during 1 hr of smoke exposure, and after 3 and 6 days of cigarette smoke treatment. Exposure to cigarette smoke reduced valine incorporation into brain and liver protein by 12 and 30% respectively. The greatest part of this reduction in synthesis was due to the hypothermie effect of smoke exposure, which was an approx. 8% change in the synthesis rate for each degree of reduction in body temperature, though a significant smoke effect was still evident. Two major components of cigarette smoke, nicotine and carbon monoxide, were individually tested. Injections of nicotine produced a similar inhibition of brain protein synthesis, with no effect on liver protein synthesis. After extraction of nicotine from the smoke by use of a Cambridge filter, only slight inhibition of brain protein synthesis was observed, which was due to the decrease in body temperature; there was still a significant inhibition in the liver. Incorporation measured, not during but after smoke exposure, was still significantly reduced, although reduction in the liver was smaller than that measured during smoke exposure. Carboxyhemoglobin at levels 50% higher than that achieved by smoke exposure had no effect on brain or liver protein synthesis; higher carboxyhemoglobin levels (300–400% higher than levels during smoke exposure) produced inhibition of liver protein synthesis. The results suggest that the slight and significant inhibition of brain protein synthesis is due to nicotine, whereas the effect on the liver is probably due to anoxia. Smoke treatment for 3–6 days suggests that there is no adaptation to these effects. Strain differences in smoke sensitivity are not related to the effect of nicotine on protein synthesis, suggesting that other mechanisms are involved in smoke sensitivity.