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Heterotopic cardiac isografts are vasculary perfused organs that maintain structural and functional integrity. We have used this model to study the time course of change in total heart and left ventricular size which results from mechanical unloading of the myocardium. When compared to the in situ (working) heart there is a 19% decrease in the size of the heterotopic (non-working) heart (P less than 0.01) as early as 3 days post-transplantation. By 14 days there is 50% decrease in the size of the transplanted heart which is maintained at this atrophic size when measured after 4 weeks. Left ventricular protein synthesis was assayed by the simultaneous in vitro perfusion of the host and transplanted hearts under identical hemodynamic conditions. The hourly incorporation of 14C-lysine into total left ventricular protein was 21 nmol in the transplant compared to 50 nmol in the in situ heart (P less than 0.01). This incorporation remained significantly lower throughout the period of study. In contrast, both the total (mumol lysine/g protein nitrogen/h) and fractional rates of protein synthesis which were lower in the transplanted left ventricle at days 3 and 7 returned to control values by day 28. The present studies demonstrate that heterotropic cardiac transplantation leads to a prompt and reproducible decline in cardiac mass and in total protein synthesis. These studies further support the role of cardiac work as an important determinant in the regulation of cardiac protein synthesis.

The effect of ethanol on the secretion of proteins was studied in hepatocytes isolated from 24-h fasted rats and from fed rats. Hepatocytes were isolated after collagenase disruption of the liver and incubated in a standard medium containing amino acids, bovine albumin, glucose, penicillin and streptomycin in HEPES buffer. Cell viability was determined by urea production and trypan blue exclusion. When studying protein export, a model had to be chosen in which the labeling is accomplished before the addition of the test agents. Cells were incubated with [3H]valine for 2.5 and 7.5 min followed by a 15-mM valine chase and the incubates were adjusted to final concentrations of ethanol of 50 mM, 100 mM, colchicine 5-50 microM or cycloheximide 18 microM. Cells and media were harvested at various times, and counts incorporated into medium and cell protein were determined. Cycloheximide inhibited protein synthesis by 99%, decreased protein secretion by 10-20%, but did not further inihibit protein labeling when given after the chase confirming the chase's effectiveness. Colchicine inhibited protein release by 27-54% depending on the dose. With control cells labeled protein and specifically albumin appeared in the medium 20 min from the start of the pulse and this release of protein was not inhibited by 50 mM or 100 mM ethanol incubated with cells from the same animal whether the donor has been fed or fasted. The values for the ethanol-treated cells ranged from 94.0 to 113% of the control values from 30 to 120 min after the addition of the pulse. Lactate levels were markedly elevated, and urea synthesis decreased in the presence of either 50 mM EtOH or 100 mM EtOH. Thus using a method that can distinguish the effect of ethanol on synthesis from secretion, it is concluded that acute exposure to EtOH does not interfere with protein secretion.

1. Reperfusion after ischemia and perfusion with total anoxia were studied in the isolated guinea pig heart model which permits right ventricular loading and constant coronary perfusion. Deprivation of oxygen in both situations resulted in a marked shift of circulation from the left to the right ventricle with markedly increased spaces of distribution of 99mTc radionuclides and albumin in the latter. 2. In view of the complexities of measuring protein synthesis during ischemia, continuous anoxic perfusion was used to evaluate this parameter in anoxic induced arrest. There was a profound fall in protein synthesis associated with this arrest, accompanied by a fall in ATP, creating phosphate, glycogen, potassium, and a rise in lactate production. The fall in protein synthesis was more marked in the left ventricle, despite the absence of work while it was still beating. 3. The changes in synthesis were almost completely prevented by initiating cardiac arrest with high K+ (16 meq/l) at the same time as anoxia; energy metabolism remained near normal, and recovery of contractility was nearly complete. 4. The studies demonstrated the differences in vascular distribution between the ventricles after ischemia or with perfusion anoxia, the possible difference in availability of substrate to the two ventricles under these conditions, as well as the difference in protein synthetic response, and further support the protective effect of potassium induced arrest on the hypoxic heart.

The occurrence of cardiomyopathy in chronic alcoholism has been well documented, but the cause of the myopathy is still unclear. Some of the mechanisms described have included accumulation of triglycerides, altered fatty acid extraction, membrane alterations with decreased response to Ca2+ and to catecholamines and alterations in cardiac protein synthesis. The present article briefly reviews the effects of ethanol or its primary metabolite, acetaldehyde, on cardiac protein synthesis and possible relation to cardiomyopathy.

Cardiac: Cardiac protein synthesis is influenced by the state of nutrition with reduction of cardiac size in starvation. Ethanol per se may not affect this synthesis directly, but the metabolite of ethanol, acetaldehyde, profoundly decreases normal protein synthesis in the heart in vitro. The interference with the synthetic process may play a role in the ultimate cardiomyopathies of malnutrition and alcoholism. Hepatic: In vivo albumin synthesis is sensitive to environment, oncotic pressure, normal balance, nutrition, as well as toxins and state of health. Thus, to study the acute effects of alcohol alone, it was necessary to employ the isolated perfused liver. Fasting reduced albumin synthesis 50%, with loss of RNA and a disaggregation of the endoplasmic membrane bound polysome. Tryptophan, arginine and ornithine added to the perfusate at a final concentration of 10 mM reversed these findings. Alcohol likewise reduced albumin synthesis; disaggregates the bound polysome without a marked loss of RNA. Ornithine, arginine and tryptophan are able to reverse this loss in albumin synthesizing capacity. The combination of fasting and alcohol, while not lowering albumin synthesis below that seen with either stress alone, prevents the recovery from either stress.