Dependence of Protein Synthesis on Aortic Pressure and Calcium Availability

Abstract

Increased aortic pressure accelerated protein synthesis in control–beating and ar- rested–drained hearts supplied with either glucose or pyruvate. Elevation of perfusion pressure from 60 to 120 mm Hg increased oxygen consumption in control–beating but not in arrested–drained preparations. Energy availability, as assessed by adenylate energy charge or creatine phosphate/creatine ratio, or both, was increased in arrested–drained hearts supplied with glucose and perfused at 60 and 120 mm Hg aortic pressure. In control–beating or arrested–drained hearts supplied with pyruvate, energy availability was not improved by elevation of aortic pressure from 60 to 120 mm Hg. An increase of perfusate calcium concentration from 0.5 to 5.0 mM in control–beating Langendorff preparations supplied with glucose and perfused at an aortic pressure of 90 mm Hg doubled oxygen consumption and decreased energy availability, but had no effect on the rate of protein synthesis. In arrested–drained hearts supplied with either glucose or pyruvate and calcium concentrations ranging from 0.5 to 5.0 mM, the rates at 120 mm Hg aortic pressure were 11–25% higher than at 60 mm Hg. These findings provide no evidence to implicate increased oxidative metabolism, energy availability, or extracellular calcium concentration as important factors in the mechanism that accounts for the effect of increased aortic pressure on protein synthesis.