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The liver manufactures albumin at a massive rate and decreases production in times of environmental, nutritional, toxic and trauma stress. Osmotic pressure is a basic evolutionary regulatory factor, and hormonal control over albumin production has been demonstrated. Where and why new or old albumin is degraded are questions which have not been clarified, although the vascular endothelium may well be the degradative site. Albumin is important as a transport protein, as a measure of evolution and as a model to study secretion following synthesis without the intervening steps of glycosylation. Investigations as to how this protein enters the endoplasmic membrane may well answer some of the questions concerning signal peptide insertion (288). The role of the urea cycle intermediate ornithine and its participation in polyamine synthesis, which has a positive effect on albumin synthesis, is under study. Likewise, the inverse relation between acute-phase protein synthesis and albumin synthesis regulated by interleukin 1 and other cytokines will merit further study. These are a few of the concepts which will be tested in the future.

RNA polymerase activity was measured in isolated cardiac nuclei subjected to hydrostatic pressure. After 20 min of pressure, Mn2+ stimulated RNA polymerase II activity was increased. The response to pressure was inhibited by low concentrations of alpha-amanitin (1.1 microgram.cm-3) an inhibitor of polymerase II activity. The data show that pressure applied to isolated nuclei stimulates RNA polymerase II activity, forming mRNA, and suggests that direct application of pressure to cardiac nuclei may be the stimulus which triggers the augmented protein synthesis seen in pressure overload.

The relative molar synthesis of cardiac contractile proteins has been measured in the perfused heart under control haemodynamic conditions. This synthesis, of myosin heavy chains, individual light chains (1 and 2), actin and tropomyosin, was determined from isolated guinea-pig hearts perfused for 3h simultaneously with constant specific radioactivities and concentrations of [3H]lysine and [3H]phenylalanine. The data strongly suggest that all of the proteins studied were synthesized from the same precursor pools of lysine and phenylalanine, since the ratio of the specific activities of the two labels was the same in all of the proteins. Measurement of molar synthesis of each contractile protein was the same with either labelled amino acid. Under control haemodynamic-perfusion conditions, the relative molar synthesis of the contractile proteins was actin greater than heavy chains greater than light chain 2 greater than light chain 1 greater than tropomyosin.

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.

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)

Increased afterload causes increased cardiac myosin synthesis and ultimately leads to hypertrophy. Since the latter is associated with altered myosin ATPase activity, it was of interest to study the synthesis of myosin subunits in the acute response to this stress. An in vitro guinea pig heart preparation was used which allowed application of afterload to the right ventricle with unaltered coronary flow, and also permitted measurement of synthesis of myosin heavy chains (HC) and combined light chains (LC) by continuous perfusion with labelled amino acids (3H-lysine and/or 3H-phenylalanine) of constant specific activity. Isolation of 3H-labelled HC and LC with heterologous unlabelled carrier was possible because of identical mobilities of HC's and LC's from unlabelled lamb carrier myosin and 3H-labelled guinea pig myosin. This permitted study of comparative synthesis of the HC and LC in small samples as the single guinea pig right ventricle (100--150 mg) and avoided errors inherent in pooling hearts or in measurement of turnover in the nonsteady state. After 3 h or perfusion, the ratio of synthesis of HC/LC was 2 : 1 in controls. This ratio increased significantly to 3 : 1 in after load. It is possible that the disproportionate increase in HC synthesis may lead to stoichiometric problems in myosin assembly which ultimately effect altered myosin ATPase activity.

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.

Liver protein synthesis involves a complex series of reactions which is influenced by hormones, nutritional state and general health of an animal. The secretory processes for proteins, such as albumin, also interact with the protein synthetic machinery of the liver. Alcohol may affect synthesis and/or secretion at a number of loci and the mechanism of alcohol's action could depend on the immediate state of the experimental tissue. Ethanol was shown to interfere with albumin synthesis and the effect was shown to differ when livers from fed and fasted animals were compared. The ethanol effects were also dependent on the metabolism of ethanol rather than on the simple presence of this drug. Acetaldehyde decreased albumin synthesis but in a manner which was distinct from the ethanol effect. Acute ethanol administration under the conditions used in our studies had little effect on secretion of prelabeled proteins from hepatocytes. The implications of studies of the effects of ethanol on liver protein synthesis and secretion are discussed.

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.

Left ventricular ejection times ( LVETs ) were obtained in a group of 20 control subjects (group 1) during maximal treadmill exercise testing, using a Bruce protocol, and in conjunction with myocardial scintigraphy. Heart rates (HRs) and LVETs were recorded during standing rest, each minute of exercise, and for eight minutes in the postexercise period. A linear regression equation was constructed and separate correction factors of 1.04 X HR + observed LVET (correlation coefficient, -.86) for the exercise period and 0.73 X HR + LVET (correlation coefficient, -.71) for the postexercise period were derived. The LVETs were also recorded in 31 subjects with positive ECGs and defects on myocardial scanning with thallous chloride TL201 (group 2) during a similar exercise protocol. Comparison of groups 1 and 2 disclosed that the former had a higher HR and shorter LVET than the latter at peak effort (consonant with the significantly longer duration of exercise achieved by the control subjects). The LVETs in group 1 remained significantly shorter than that of group 2 through the fifth minute postexercise. In the postexercise period, the LVET indexes were significantly shorter in group 1 than group 2 at 1, 3, and 5 minutes. Subjects with presumptive coronary disease (positive ECG and defects on thallium 201 scanning) not only have a decreased exercise tolerance and HR, but after exercise, their ejection times are substantially longer than in normal subjects. This may be attributed to a slower rate of ejection in patients with coronary disease when venous pooling on quiet standing after exercise delivers a smaller volume to the heart. In normal subjects, the lesser volume may be ejected more rapidly.

Cardiac stress produced by hypertension or excess volume loading results in different types of hypertrophy. Elevated left ventricular pressure rapidly results in increased myocardial protein synthesis in vivo and in vitro, but such rapid alterations are not consistently seen in volume loading. The difference in response is difficult to clarify since it is not possible to effect alterations in left ventricular pressure or perfusion without profoundly affecting coronary perfusion. The present study describes cardiac protein synthesis in the right ventricle of the young guinea pig heart in vitro by utilizing a perfusion model in which the right ventricle could be stressed by elevations of pressure or volume loading in the presence of constant and restricted coronary perfusion. With coronary flow maintained at 4 ml/min per heart equivalent to 25 ml/min/g dry wt, an increase in right ventricular pressure from normal levels of 3 mm Hg to 11 mm Hg resulted in a 60 percent increase of myocardial incorporation of (14C)lysine into protein. However, with further increases of right ventricular pressure to 22 mm Hg, protein synthesis dropped back to normal levels. The falloff in protein synthesis was not due to decreased contractility, alterations in intracellular lysine pool specific activity, or alterations in distribution of coronary flow. a 60 percent increase in coronary perfusion was again associated with a similar response of protein synthesis to progressive elevations of pressure despite a rise in the ATP levels and a fall in lactate production. Thus, a deficiency of O2 did not entirely explain the decline of protein synthesis with maximal pressures. At all levels of coronary perfusion, volume loading for 3 h did not result in increased protein incorporation of (14C)lysine. The studies support a relationship between ventricular pressure and protein synthesis unrelated to coronary flow per se. A pressure receptor triggering protein synthesis within the ventricular wall is postulated. Such a relationship is not apparent in short-term volume loading in vitro.

Prolonged ingestion of ethanol may lead to a cardiomyopathy, and studies in the experimental animal have demonstrated alterations in protein metabolism. These changes include depression of protein synthesis with acetaldehyde in the acute experiment, in vitro, and after chronic ethanol ingestion in vivo. The present studies were initiated to see if the inhibition of protein synthesis following prolonged ethanol ingestion involved myocardial contractile proteins. Newly weaned guinea pigs, weighing 350 g, were placed on a regimen of normal laboratory diet with 10% ethanol in the drinking water. Calorie-matched controls, drinking dextromaltose in the water, were simultaneously run. After 40 weeks of ingesting 10% ethanol in the drinking water, hearts from growing guinea pigs were removed and synthesis of myocardial contractile proteins (myosin heavy chains, light chains (LC1, LC2), actin, and tropomyosin) assayed in vitro with 3H-labeled amino acids. With aging, there was a decrease in the rates of synthesis of all the contractile proteins. After 40 weeks of ethanol ingestion, the synthetic rates of myosin heavy and light chains and tropomyosin were the same as in calorie-matched controls, but the synthetic rate of actin was significantly decreased by 20% (p less than 0.01). This decrease in actin synthesis may be the first indication of ultimate inhibition of synthesis of all the contractile proteins which may lead to myofibrillar disorganization and vacuolization reported after chronic ethanol ingestion.

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 influence of alcohol on albumin synthesis was studied in the isolated perfused rabbit liver. Carbonate-(14)C was used to label the intracellular arginine pool which serves as the precursor of both the carbon of urea and the guanido carbon of arginine in albumin. The control group synthesized albumin at a rate of 33 mg/100 g of wet liver weight during 2.5 hr of perfusion. When alcohol, 220 mg/100 ml, was added to the perfusate, albumin synthesis decreased to between 7 and 11 mg, less than one-third the control rate. The addition of 10 mM tryptophan to perfusates containing alcohol prevented most of the inhibitory effects and albumin synthesis increased to average 24 mg. Further, the addition of alcohol to the perfusate decreased the hepatic protein/DNA ratio from 70 to 54 and the RNA/DNA ratio from 2.3 to 1.8, changes equivalent to those seen after a 24 hr fast. The addition of tryptophan to the perfusate prevented these findings in both instances. Endoplasmic membrane-bound polysomes were examined for aggregation. Alcohol decreased the quantity of heavier aggregates. Reaggregation occurred when tryptophan was added but quantitative changes in albumin synthesis could not be related to the degree of reaggregation.