Preoperative use of sotalol versus atenolol for atrial fibrillation after cardiac surgery

BACKGROUND

Atrial fibrillation is one of the most common complications of cardiac surgery. Beta blockers have been demonstrated to decrease the incidence of postoperative atrial fibrillation. Preliminary investigations reporting sotalol and atenolol to be effective in preventing postoperative atrial fibrillation are encouraging, but no studies have been conducted comparing both drugs.

METHODS

A total of 253 consecutive eligible patients (66 +/- 8 years; mean +/- standard deviation) scheduled to undergo cardiac surgery were enrolled in this study. Patients were randomized in a prospective open manner 1.5:1 to atenolol group (50 mg/daily; 153 patients) or sotalol group (80 mg twice daily; 100 patients).

RESULTS

Atrial fibrillation occurred in 44/253 patients (17.45%). A significant difference was found in the occurrence of atrial fibrillation in the atenolol group (34 patients, 22%) compared with those receiving sotalol (10 patients, 10%; p = 0.013). Therapeutic efficiency and efficacy was 12% and 54%, respectively. Stepwise logistic regression analysis revealed that age more than 68 years old (odds ratio = 2.72; 95% confidence interval [CI] = 1.37-5.41; p = 0.004), the use of beta-adrenergic agents (odds ratio = 2.74; 95% CI = 1.5-5; p = 0.001), and sotalol (odds ratio = 0.46; 95% CI = 0.23-0.95; p = 0.035) were independently associated with development of atrial fibrillation.

CONCLUSIONS

Oral low-dose sotalol provides a considerable reduction in the occurrence of atrial fibrillation. A selective approach based on clinical risk prediction should decrease the occurrence of atrial fibrillation after cardiac surgery.

Effect of caffeine on urea biosynthesis and some related processes, ketone bodies, ATP and liver amino acids

An increase in urea synthesis has been found in rats administered large doses of caffeine. A parallel increase in urea biosynthesis was also found in hepatocytes isolated from caffeine-treated rats, which confirms a greater capacity for urea synthesis induced by caffeine. This increase appeared only after some days of caffeine treatment; during the first days there was no increase in serum urea levels or in in vitro studies of urea synthesis in isolated hepatocytes. However, no appreciable changes were found in either cytosolic or mitochondrial redox states, or in ATP levels in in vivo and in vitro studies. A parallelism was observed between the decreased amino acid levels in caffeine-treated rats and in isolated hepatocytes incubated with different concentrations of caffeine. Several possible mechanisms to explain these findings are considered in the discussion.

In vitro effect of caffeine on some aspects of nitrogen metabolism in isolated rat hepatocytes

Long-term exposure to high doses of caffeine affects several aspects of nitrogen metabolism, such as purine, pyrimidine and urea synthesis. However, little is known about the mechanisms of these changes and if they occur at shorter term. We have studied in isolated hepatocytes: 1) the in vitro effect of high doses of caffeine on amino acid levels, 2) the main destination of ammonia and carbon chains from amino acid catabolism, and 3) the cytosolic and mitochondrial redox states. We have found that, whereas it has a small effect on urea synthesis and on the levels of the cofactors and intermediates, it decreases the levels of several amino acids, the gluconeogenesis and the redox state. Our results suggest that a longer exposure to caffeine is necessary to affect the normal functions of some metabolic pathways.

Long-term high-protein diet induces biochemical and ultrastructural changes in rat liver mitochondria

We have shown in previous work that long-term high-protein diet treatment (420 days) induces important biochemical and stereological changes in rat liver mitochondria. In this paper we have studied the time course for these changes in rats fed a high-protein diet for 30, 90, 180, and 420 days. The liver carbamoyl-phosphate synthetase I (ammonia), which represents 15-20% of the mitochondrial protein, increased ca. 2.5-fold in 30 days, with no further significant changes during the treatment. This increase was accompanied by an increment in the serum urea levels and a diminution in the half-life of blood urea, which could be interpreted as compensatory mechanisms for detoxification of blood and for maintaining osmotic pressure. The stereological study indicates that there is an enlargement of individual mitochondria in rats fed the high-protein diet, and that the maximum enlargement occurred at 90 days of treatment. The analysis of data shows, however, that the increase in mitochondrial volume density was due mainly to proliferation of normal mitochondria. These mitochondria were functionally normal as demonstrated by the unaltered P:O ratio during treatment. The total content of liver amino acids was increased, and the taurine/glycine ratio (which has been related to metabolic stress) was greatly increased. The possible correlation between the increases of both liver taurine levels and cell volume is discussed.

[Arginase deficiency, congenital hypothyroidism and hepatic fibrosis]

A new case of arginase deficiency in a newborn is reported. In contrast with previous cases, this infant showed severe protein intolerance of early onset. Diagnosis was based on the assay of urea cycle enzymes in a postmortem liver sample and on arginase activity in erythrocytes of parents and sister of the patient. "Pedigree" shows that arginase deficiency in this family presents a dramatic course. Congenital hypothyroidism with athyreosis, moderate hepatic fibrosis and megamitochondria are present in the same subject. Possible significance of these findings is briefly discussed.

Rats fed prolonged high protein diets show an increase in nitrogen metabolism and liver megamitochondria

Rats were fed diets containing 20, 50 and 80% protein for 14 months. The urea excreted by the rats fed diets containing 50 and 80% protein when compared to rats fed diets containing 20% protein increased ca. 2- and 3-fold, respectively, in ca. 2 days; this increase was maintained essentially unchanged through the experimental period. The serum levels of urea increased 2.5- and 4-fold, respectively, in the first days and were also maintained during the experiment. Glutamate dehydrogenase activity of liver remained unchanged. The five urea cycle enzymes increased with respect to the control values. Orotic acid excretion increased as well as orotidylate decarboxylase and orotate phosphoribosyltransferase, but aspartate transcarbamylase did not. The key amino acids involved in the urea and pyrimidine pathways in liver were also measured; aspartic and glutamic acids and citrulline were increased, and ornithine and arginine did not change with the higher protein intake. In general, no differences were observed between animals fed 50 and 80% protein in their diets. Protein synthesis did not increase with the increase of protein content of the diet. Stereological analysis of ultrathin sections showed that the high protein diet induced a significant increment in the volumetric density, numerical density and size of hepatocyte mitochondria. Moreover, the presence of giant mitochondria, a hundred times larger than normal, was also observed in some periportal hepatocytes of rats fed the 80% protein diet.

Inhibition of ureogenesis in isolated rat liver cells by a non-steroidal anti-inflammatory drug (butibufen)

The effect of a non-steroidal anti-inflammatory drug (butibufen) on ureogenesis in isolated rat hepatocytes has been studied. Butibufen at 0.4 mM, and particularly at 2 mM, strongly inhibited urea synthesis. The drug at these concentrations also inhibited markedly carbamoylphosphate synthetase activity. In addition, 2 mM butibufen lowered ATP concentrations of the cells and enhanced oxygen consumption in isolated liver mitochondria. The results suggest that the inhibition by 0.4 mM butibufen on carbamoylphosphate synthetase activity can account for the entire inhibition of ureogenesis, whereas the decreased cellular ATP concentration at 2 mM butibufen might be at least partly responsible for low carbamoylphosphate synthesis and thus, for reduced urea production. The decrease in ATP levels probably results from uncoupling effects of butibufen on oxidative phosphorylation.

A new case of arginase deficiency in a Spanish male

A new case of arginase deficiency is reported in a male newborn from Spain. In contrast with the majority of the earlier cases, this infant showed severe protein intolerance of early onset. The diagnosis was based on the assay of the urea cycle enzymes in a postmortem liver sample. Levels of erythrocyte arginase were also determined in the parents and in a sister of the patient, and were consistent with heterozygosity. From a study of the pedigree it appears that arginase deficiency in this family presents a dramatic course.

Caffeine-induced changes in the composition of the free amino acid pool of the cerebral cortex

The free amino acid content in the cerebral cortex of rats administered caffeine orally, and with automutilation behavior similar to that observed in the Lesch-Nyhan syndrome, have been measured. Amino acids significantly elevated were taurine, histidine and aspartic acid, whereas tyrosine showed a significant reduction. There was no change in the concentration of gamma-aminobutyric acid and glutamic acid. It has been conjectured that changes in amino acids levels in the cortex might be responsible for the pharmacological action of caffeine and for the progressive behavior abnormalities observed in these rats. Interestingly these results are similar to these found recently in experimental uremia.

Acute and chronic effects of carbamyl glutamate on blood urea and ammonia

Carbamyl glutamate injected into normal rats produced no change in blood urea levels. Rats fed a high-protein diet or starved for 48 h had increased blood urea. Carbamyl glutamate injection induced a further increase in the levels of urea in their blood. Also, carbamyl glutamate administered in the drinking water of normal mice produced an increase in blood urea, which was accompanied by a decrease in blood ammonia. The application of these findings to the treatment of urea cycle enzymopathies is discussed.

Lesch-Nyhan syndrome, caffeine model: increase of purine and pyrimidine enzymes in rat brain

Rats ingesting high doses of caffeine reproduce the self-destructive behaviour observed in the Lesch-Nyhan syndrome. This syndrome includes a deficit in hypoxanthine-guanine phosphoribosyltransferase. We have observed, however, that the activity of hypoxanthine-guanine phosphoribosyltransferase increases in direct proportion to the concentration of caffeine found in rat brain. It appears, therefore, that the caffeine model is not a true model for the Lesch-Nyhan syndrome, or alternatively, that the deficit in hypoxanthine-guanine phosphoribosyltransferase is coincidental and not a main key to the multifarious aspects of the syndrome, particularly the self-mutilation. The possibility that levels of dopamine are increased in the caffeine model are discussed as a basis for the destructive behaviour. We have found also that ingestion of large amounts of caffeine increases the activities in rat brain of adenosine deaminase, purine nucleoside phosphorylase, aspartate carbamoyl-transferase, dihydroorotase, and dihydroorotate oxidase.

Inhibition by N-acetyl-aspartate of aspartate binding to a proteolipid fraction from rat cerebral cortex

Many roles have been suggested for N-acetyl-aspartate in brain function because of it being located almost exclusively in that organ. However, its true role remains to be demonstrated. We show here that N-acetyl-aspartate: 1) binds to a hydrophobic protein fraction from the cerebral cortex of the rat, which specifically binds L-aspartate, L-glutamate, and gamma-amino-butyric acid; and 2) has a marked inhibitory effect on the aspartate binding sites of this proteolipid fraction. Structural analogs of N-acetyl-aspartate, i.e. N-carbamyl-aspartate and N-methyl-aspartate also inhibit the L-aspartate binding by the brain protein fraction used.

Effect of starvation on the N-acetylglutamate system of rat liver

Rats fasted for 3 and 6 days showed an increase in the activity, per g of liver but not per total liver, of the mitochondrial urea cycle enzymes, carbamylphosphate synthetase and ornithine transcarbamylase. The activity of N-acetylglutamate synthetase, both per g and per total liver, increased by the third day and then decreased on the sixth day of fasting. The cytosolic enzyme N-acetyldeacylase showed the same general pattern as the N-acetylglutamate synthetase except that the relative proportion of synthetase over deacylase was higher at the third day of starvation. The N-acetylglutamate level/g liver increases in relation to the number of days of fasting.

Effects of N-acetyl aspartate, aspartate, and glutamate on cAMP and cGMP levels in developing rat cerebral cortex

N-Acetyl-aspartate (N-Ac-Asp) incubated with minced cerebral cortex caused a dose-dependent increase in the levels of cAMP and cGMP. This effect was followed during postnatal development. N-Ac-Asp elicits the greatest increase in cAMP in 5-day-old and in cGMP in 40-day-old rats. The levels of cyclic AMP were always higher than those of cGMP. We also studied the effects of L-aspartate (Asp) and L-glutamate (Glu) on the levels of cyclic nucleotides in the cerebral cortex minces of rats different ages, and observed that both amino acids produced the maximum increase in cAMP at 10 days, whereas in the case of cGMP the maximal effect of Asp occurs earlier than 20 days and of Glu after 40 days. In the adult rat, the N-Ac-Asp effect on cAMP was greater than that produced by either Asp or Glu, whereas the levels of cGMP were similarly affected by all three. The data show a peak response of cAMP and cGMP to N-Ac-Asp, Asp, and Glu during cortical maturation. Because this response varies with postnatal time, N-Ac-Asp, and Glu may act upon different receptor sites.