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Albumin synthesis was studied in the isolated perfused rabbit liver under the influence of the stresses of fasting and acute alcohol and acetaldehyde exposure. Fasting clearly depressed albumin production and disaggregated the endoplasmic membrane-bound polysomes. Acute exposure to alcohol produced the same results. Acetaldehyde 2 mg% resulted in a depression of albumin synthesis but the polysomes were not disaggregated. The metabolism of alcohol was necessary for polysome disaggregation. The acute effects of ethanol and fasting were quite similar and it might be considered that the alcohol was acting like a pharmacologic fast. Employing the liver from a fasted donor specific amino acids infused into the liver at levels of 10 mM reversed the acute effects of fasting and the acute effects of exposure to ethanol. However when the two stresses of fasting and alcohol were combined the same amino acids were not effective. In studying albumin synthesis and/or secretion it is necessary to carefully define the nutritional status of the experimental model.

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.

Acetaldehyde infusions inhibit albumin synthesis in the liver from fed donors but not in the livers from fasted donors. The inhibition of acetaldehyde metabolism with 4-MP and disulfiram reverses this finding, suggesting that acetaldehyde per se is not the toxic agent. Disulfiram stimulates albumin synthesis in livers from fasted donors, and the presence of acetaldehyde does not prevent this process. The effects of ethanol infusions cannot be explained as due to the presence of acetaldehyde; some intermediate metabolic step may be the basis of the inhibition of albumin production and polysome disaggregation in the presence of ethanol.

Sucrose and ethanol inhibit albumin synthesis; sucrose via an osmotic mechanism and ethanol during its metabolism. The present study was undertaken to compare the effects of both of these agents on albumin synthesis and secretion, and to see if ethanol inhibition could be related to an osmotic effect. Male, fed rabbits served as liver donors in all studies. There were a total of 35 studies: 13 control; 10 ethanol (39 to 52 mM); 4 cycloheximide (0.5 mM), and 8 sucrose (1%). Plasma volume was measured with 125I-albumin (human) and extracellular volume measured with either 99mTc diethylenetriamine pentaacetic acid or [14C]sucrose. During perfusion, rabbit albumin content in the perfusate was measured immunologically every 15 to 30 min for 225 min. Interstitial albumin efflux was measured by the rate of appearance in the perfusate of 125I-albumin given to 10 other rabbits 3 days prior to hepatic removal and perfusion. During the initial 75 min of perfusion, 74% of the in vivo equilibrated exchangeable 125I-albumin appeared in the perfusate, and during this period the rabbit albumin that entered the perfusate was taken to represent efflux from the interstitial volume plus synthesis. Rabbit albumin appearing in the perfusate during the later period of 150 min was taken to represent mainly synthesis and was used to calculate the amount of albumin that would be synthesized in 75 min. The difference between these two values would be hepatic interstitial albumin appearing in the perfusate.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Albumin synthesis is stimulated by those amino acids which increase urea synthesis and membrane bound polysome aggregation. Ornithine, an amino acid not incorporated into protein and produced from arginine in the urea cycle, is an albumin-stimulating amino acid and is the precursor of the polyamines, and we have shown that the polyamine spermine promotes bound polysome aggregation. To test the concept that ureogenesis with its generation of ornithine might play a key role in albumin synthesis regulation via the polyamine pathway, isolated livers from fasted donors were perfused with ornithine, alpha-difluoromethyl ornithine (DFMO), and spermine. In control experiments, albumin synthesis was 13.4 +/- 0.8 mg per 100 gm liver per hr and polysome aggregation was 47%. These were increased in the presence of ornithine (26.0 +/- 2.6 mg and 59%); if the livers were preperfused with DFMO before the addition of ornithine, then the expected increase in albumin synthesis and polysome reaggregation did not occur (16.3 +/- 1.4 mg and 47%). However, if spermine was present with DFMO during the preperfusion, then the addition of ornithine had the expected effect (albumin synthesis = 26.1 +/- 1.2 mg and polysome aggregation = 62%). This suggests that if the ornithine to putrescine pathway is blocked, ornithine does not stimulate albumin synthesis and offers support to the concepts that (a) ornithine stimulation of albumin production is via polyamine synthesis and (b) that the urea cycle plays a more important role in protein metabolism than simply the pathway for nitrogen disposal.

The transport of plasma albumin and newly made albumin into ascitic fluid was studied in eight patients with cirrhosis and ascites. The thoracic duct was cannulated in two patients and lymph collected over a period of 2 hr. Simultaneously albumin-(131)I and carbonate-(14)C were injected intravenously. The albumin-(131)I measured the transfer of plasma albumin into ascites and into thoracic duct lymph. The carbonate-(14)C, by labeling newly formed albumin, permitted the estimation of the transfer of newly formed albumin into plasma, ascites, and lymph. If the newly synthesized albumin entering ascites and thoracic duct lymph is delivered initially into the plasma, then the ratios of the albumin-(14)C and -(131)I in ascites and lymph compared with the content of albumin-(14)C and -(131)I in plasma would be identical. However, if some newly formed albumin is delivered directly into ascites or lymph, the ratio for albumin-(14)C would be higher than that for albumin-(131)I in lymph or ascites. The ratios of both labeled albumins found in ascites or lymph are expressed as per cent of the total plasma pool. In the eight patients studied 4.2-11.7% of the albumin-(14)C in plasma was found in ascites in 2 hr whereas only 0.4-2.2% of plasma albumin-(131)I entered in this same period. In the two patients studied during thoracic duct lymph drainage 6.1 and 13.5% of newly made albumin-(14)C appeared in lymph in 2 hr whereas only 2.8 and 3.8% of plasma albumin-(131)I was found in the lymph. In cirrhosis with ascites some newly formed albumin entered ascites and thoracic duct lymph by a direct pathway from the liver bypassing the systemic circulation.

The effects of CCl(4) on albumin synthesis were studied employing the isolated perfused liver. Carbonate-(14)C was used to measure newly synthesized albumin. 2.5 ml of CCl(4) was administered by stomach tube 2 hr before perfusion. Albumin synthesis decreased from 36 to 5 mg following the ingestion of CCl(4). Preperfusing the livers for 1 hr before measuring albumin synthesis resulted in an increase to 12 mg, and the addition of tryptophan to a final concentration of 10 mM resulted in a further increase to 19 mg. Cortisone did not protect against the toxic effects of CCl(4) when administered to the donor rabbits. Fasting resulted in an increased sensitivity to CCl(4) and an antioxidant was not effective in protecting against the toxic manifestations of CCl(4).

Carbonate-(14)C was used to label the hepatic intracellular arginine pool and direct measurement of albumin synthesis was made in six rabbits before and after an 18-36 hr fast. 18 perfusion studies were performed with livers derived from fed and fasted rabbits (18-24 hr). Microsomal amino acid-incorporating ability with leucine-(3)H and phenylalanine-(14)C was compared in 17 studies, using microsomes isolated from livers taken from fed and fasted rabbits and from isolated perfused livers whose donors were fed and fasted. Albumin synthesis is rapidly inhibited by fasting. Albumin synthesis decreased 33% in vivo and 53% in the perfused liver. The microsomes from perfused livers taken from fed animals did not demonstrate a significantly reduced capacity to incorporate leucine-(3)H or phenylalanine-(14)C into protein. Microsomes derived from perfused and nonperfused livers whose donors were fasted incorporated 32-54% less tracer than microsomes obtained from fed donor rabbits. Microsomes separated from perfused livers removed from fed and fasted rabbits responded to polyuridylic acid stimulation and phenylalanine-(14)C incorporation rose from 58 to 171%. An 18-36 hr fast inhibits albumin production in vivo and in the perfused liver. The microsomal system is less active in the fasted state and perfusion per se does not inhibit the microsomal response.