Effect of dipyroxime on the concentration of nicotinamide coenzymes and adenylate nucleotides in the myocardium and liver of rats poisoned with phthalophos]

Experiments were conducted on rats; in depression of blood cholinesterase activity by 68.6 percent phthalafos proved to decrease the myocardial nicotinamide coenzymes content on account of reduction in the amount of the oxidized forms. In the liver phthalafos diminished the content of oxidized and reduced forms of nicotinamide coenzymes, decreased the level of adenylic nucleotides chiefly at the expense of ATP. Diproxim prevented the changes caused by phthalafos in blood cholinesterase reactivation to 47.5 percent. It is supposed that the capacity of diproxim to normalize the oxidative processes in the cell by acting upon the nicotinamide coenzymes and adenylic nucleotides underlies its antidote action.     

Metabolism of the pyridine nucleotides involved in nicotinamide adenine dinucleotide biosynthesis by Clostridium butylicum

In order to elucidate the mechanism of the accumulation of considerable amounts of free nicotinic acid (NA) in the culture medium of Clostridium butylicum, this organism was investigated with regard to its ability to metabolize nicotinamide adenine dinucleotide (NAD) and its immediate biosynthetic precursors, nicotinic acid mononucleotide (NAMN) and nicotinic acid adenine dinucleotide (deamido-NAD). Cell-free extracts of C. butylicum were found to degrade NAMN and deamido-NAD to NA. NAMN, in the presence of adenosine triphosphate (ATP), was converted to deamido-NAD, but only at high concentrations of ATP (20 mM) was significant synthetic activity observed in competition with NAMN degradation. Degradation of both NAMN and deamido-NAD was activated by ATP at concentrations of 5 and 10 mm. Anaerobiosis markedly enhanced the degradation of the nucleotides. The data indicate that the synthesis of NAMN and deamido-NAD prevails over their degradation only in the presence of high concentrations of ATP. NAD was degraded to nicotinamide mononucleotide (NMN) by a pyrophosphatase. Phosphate markedly inhibited both the deamido-NAD and NAD pyrophosphatases. Under anaerobic conditions there was practically no further degradation of NMN to NA, whereas barely measurable amounts of NA were formed under aerobic conditions. All of these observations suggest that, under the given conditions of anaerobiosis and physiological phosphate concentrations, there is very little degradation of NAD to NMN and practically no degradation to NA by C. butylicum. Thus, NAD represents an insignificant source of the NA accumulated in the culture medium. The intermediates in the biosynthetic pathway (NAMN and deamido-NAD) have been shown to be the major source of the NA which is accumulated by C. butylicum.     

Adenine nucleotides and the adenylate kinase equilibrium in livers of foetal and newborn rats

1. Measurements of ATP, ADP and AMP concentrations in livers of rats that had been delivered by Caesarian section indicate a rapid shift from a low to a high [ATP]/[AMP] ratio. This change is consistent with the cessation of glycolysis and the initiation of gluconeogenesis at birth. 2. When newborn animals are exposed to a 100% nitrogen atmosphere the hepatic ATP concentration falls and AMP increases. 3. Calculations of the [ATP][AMP]/[ADP](2) ratio give values that are close to the equilibrium constant of adenylate kinase except when the ATP concentration is high. 4. This difference cannot be accounted for by the preferential binding of available Mg(2+) to ATP(4-) rather than ADP(3-). It is concluded that the relative proportions of adenine nucleotides at any level of phosphorylation are only partly regulated by adenylate kinase.     

The effect of different hormonal conditions on the concentration and oxidoreduction state of the nicotinamide nucleotides of rat liver

1. A method is described for the determination of the oxidized and reduced forms of the nicotinamide nucleotides by measuring the rate of the oxygen uptake with an oxygen electrode in a system in which the nucleotide acts as the rate-limiting carrier in a cyclic system. 2. The method permits the measurement of quantities as low as 0·02μg. of NAD⁺ or NADH or 0·01μg. of NADP⁺ or NADPH. 3. The method permits the measurement of the nucleotides in extracts that contain non-specific reducing substances, coloured compounds or fluorescent materials, e.g. green leaves. 4. The results obtained by the present method are compared with those reported in the literature.     

Cyclic nucleotides levels in the liver of rats treated with CCl4.

Treatment of rats with two different doses of CCl4 (respectively 2.5 and 0.5 ml/kg body wt. intragastrically) is followed by a rapid increase in the cAMP content of the liver. With 0.5 ml of CCl4, the increase occurs as early as 30 min after poisoning, namely about 4-5 h before the onset of triglyceride accumulation in the liver. The maximum increase has been at 6 h after administration of the hepatotoxin. In both experimental conditions, normal values are recovered only after 36-48 h. cGMP level appears unmodified during the whole observation period. Therefore the ratio cGMP/CAMP decreases consistently. The ATP level decreases significantly between 2 and 12 h. The increase in liver triglycerides level after CCl4 can be also a consequence of an impairment of microtubule function, leading to a decreased release of lipoprotein micelles from hepatocytes into the blood stream.     

The estimation of the oxidized and reduced forms of the nicotinamide nucleotides

1. A method is described for the determination of the oxidized and reduced forms of the nicotinamide nucleotides by measuring the rate of the oxygen uptake with an oxygen electrode in a system in which the nucleotide acts as the rate-limiting carrier in a cyclic system. 2. The method permits the measurement of quantities as low as 0·02μg. of NAD⁺ or NADH or 0·01μg. of NADP⁺ or NADPH. 3. The method permits the measurement of the nucleotides in extracts that contain non-specific reducing substances, coloured compounds or fluorescent materials, e.g. green leaves. 4. The results obtained by the present method are compared with those reported in the literature.     

Increased urinary excretion of pyrimidine and nicotinamide derivatives in rats treated with methyl methanesulphonate

Rats treated with methyl methanesulphonate (MMS) excreted significantly higher quantities of deoxycytidine, thymidine, uracil, 1-methylnicotinamide (1-meNmd) and 1-methyl-6-pyridone-3-carboxylamide (6-pyr-1-meNmd) in their urine 0–24 h after MMS injection (100 $\text{mg}\text{kg}$). Excretion of thymidine, which was not detectable in untreated rats, was dose-dependent. No increase in urinary 7-methylguanine was found, and creatinine excretion was decreased by MMS treatment. Experiments with methyl-¹⁴C-labelled MMS showed transfer of ¹⁴C-label to 7-methylguanine and 1-meNmd. X-Irradiation (500 rad) caused increased excretion of pyrimidines, like MMS, but did not increase excretion of the nicotinamide derivatives.