Search

CCl4, 2.5 ml/kg body weight, was administered via a gastric tube to fed rabbits 2 hr before the livers were removed and perfused. Electron microscope studies of the liver showed that CCl4 caused a decrease in the rough endoplasmic reticulum and an increase in the smooth reticulum. The reticulum was dilated and vesiculated with few attached ribosomes. Sucrose gradient analysis of the endoplasmic reticulum bound polysomes showed them to be considerably disaggreated, and albumin synthesis and 14C-incorporation into proteins secreted into the perfusate were decreased. These effects were partially reversed when these livers were perfused with either 1 mM spermine of 10 mM arginine. Perfusion with both arginine and spermine increased endoplasmic reticulum bound polysome aggregation to about 92% of control and albumin synthesis increased from a low of 3.3 mg/100 g wet liver weight to 8.2 mg/hr or 37% of control. 14C-Incorporation into total hepatic protein and secretory proteins increased as well. The combination of spermine and arginine was more effective in stimulating albumin synthesis than either agent alone. The ability of spermine to partially reverse a specific toxic effect of carbon tetracholoride, namely polysome disaggregation, and to stimulate protein production is noted.

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.

The effects of alcohol and spermine on albumin synthesis and polysome aggregation were studied in the isolated perfused rabbit liver system. Fed or fasted males served as donors and the perfusate contained, singly or in combination, alcohol, 200 mg per 100 ml, spermine, 1 mM, and arginine, 10 mM. The results indicate that in the presence of alcohol, using a liver from a fed donor, albumin synthesis is depressed from 16 to 6 mg per 100 g of wet liver weight per hr and the bound polysome is disaggregated. Spermine partially reaggregates the bound polysome and a combination of spermine and arginine augments albumin synthesis to the control rate. When the donor is fasted, and alcohol is present in the perfusate, the addition of spermine results in aggregated bound and free polysome patterns, whereas the combination of arginine and spermine is necessary to restimulate albumin synthesis. The results indicate that spermine plays an important role in the integrity of the polysome system and that arginine and spermine appears synergistic in maintaining albumin synthesis.

Elevated levels of serum albumin have been noted in patients on chronic methadone maintenance and in heroin addicts. This observation was investigated in rabbits maintained on daily methadone 4 mg per kg of body weight after a period of 3 months on increasing dosage to assure drug tolerance. Albumin distribution and metabolism were measured with tested lots of 125I rabbit albumin. Studies were made before and again after the attainment of the methadone maintenance state. Albumin distribution was altered markedly with a shift of intravascular albumin to extravascular sites. Associated with this change, the serum albumin level rose by an average of 0.5 g per 100 ml. Albumin degradation increased by 32% from 248 to 327 mg per kg per day. The total exchangeable albumin pool increased 35%, or 3.6 g. Since the exchangeable albumin pool increased in the face of an increment in albumin degradation, albumin synthesis must have increased even further to account for this change. Although the specific factors responsible for these alterations in albumin metabolism and distribution are not known at present, to date, this hyperalbuminemic hypercatabolic state is not produceable in any other clinical or experimental situation.

The effects of ethanol, 4-methylpyrazole (4-MP), and acetaldehyde on albumin and urea synthesis, and on polysome aggregation were studied in isolated perfused rabbit livers. Fed or fasted males served as donors and the perfusate contained ethanol, 200 mg per 100 ml, with and without 1.5 mM 4-MP; or acetaldehyde, 2 mg per 100 ml, with and without 1.5 mM 4-MP. The results indicate that in livers from fed donors ethanol depressed albumin and urea synthesis and bound polysomes were disaggregated. Perfusion with acetaldehyde caused a similar decrease in albumin and urea synthesis, but did not cause polysome disaggregation. The addition of 4-MP to the ethanol perfusates did not enhance albumin or urea synthesis but did prevent polysome disaggregation. When the donor was fasted, the addition of 4-MP to the ethanol perfusates restored urea synthesis and polysome aggregation to fasted control levels. In the livers from fasted donors, acetaldehyde did not lower albumin or urea synthesis and had no effect on polysome aggregation. The results indicate that the hepatic responses to ethanol and acetaldehyde are different if the livers are derived from fed or fasted donors, and it is not possible to ascribe the toxic effects of acetaldehyde or ethanol on albumin and urea synthesis to either agent, per se.