Changes In Adenine Nucleotide Content Research Articles

Muscle performance and adenine-nucleotides status in MCA-sarcoma tumor-bearing rats

The reduction in DNA, RNA, amino acid, and total protein in muscle tissue of tumor-bearing rats may influence muscle function. The effects of MCA-sarcoma tumor burden on muscle performance and adenine nucleotides was evaluated in three fiber types of skeletal muscle. Twenty-one days after MCA-sarcoma tumor inoculation, the gastrocnemius-soleus muscle group of Fischer 344 rats was stimulated using an in situ preparation; tetanic stimulation for 10 min at 7.5, 15, or 30 tetani per min (TPM) or 60 TPM for 5 min ( n = 6 control and six tumor-bearing rats/group). ATP, ADP, AMP, IMP, phosphocreatine, and creatine content in white and red gastrocnemius muscle and soleus muscle was measured. There were no differences among controls and tumor-bearing rats in force output; however, ATP content in the soleus muscle of tumor-bearing rats was significantly reduced after 30 TPM for 10 min or 60 TPM for 5 min. The performance of skeletal muscle, over a wide range of stimulation frequency, in tumor-bearing rats does not appear to be influenced by changes in adenine nucleotide content.

Effects of acute alcohol intoxication on gluconeogenesis and its hormonal responsiveness in isolated, perfused rat liver

Rats were acutely administered ethanol as a primed constant infusion in order to produce sustained blood ethanol levels of 8–12 or 55–65 mM. At the end of ethanol infusion the livers were either freeze-clamped in vivo or isolated and perfused for metabolic studies. The rate ofgluconeogenesis and its responsiveness to phenylephrine (10μM), prostaglandin F 2α (5μM) and glucagon (10 nM), as well as the redox state of the cytosolic NAD +-NADH system were assessed in livers isolated from acutely ethanol-treated rats, and subsequently perfused without ethanol. For liver clamped in vivo, high- but not low-ethanol treatment decreased the ATP content by 31% and slightly increased ADP and AMP content, resulting in a decreased energy charge (11%). Glutamate and aspartate content was also increased in high-dose ethanol-infused rats with no changes in malate and 2-oxoglutarate content. Gluconeogenesis with saturating concentrations of lactate (4 mM) + pyruvate (0.4 mM) was delayed in reaching a plateau in the livers of high-dose ethanol-treated rats and its response to all three stimulators was impaired. Low-dose ethanol treatment only decreased the liver response to phenylephrine. While the perfused livers of low-dose ethanol-treated rats displayed no changes in adenine nucleotide content, the livers of high-dose ethanol-treated rats had a decreased ATP (35%) and an increased AMP (77%) content, paralleled by a fall in the total adenine nucleotides (14%) and energy charge (14%). No differences were observed between the saline- and ethanol-treated rats with respect to malate-aspartate shuttle intermediate concentration in perfused livers. Also, the livers of high-, but not low-dose ethanol-treated rats had a more negative value of NAD +-NADH redox state as compared to the livers of control rats. The data suggest that acute ethanol intoxication produces changes in liver metabolism and its responsiveness to hormones/agonists that are demonstrable for at least 2 hr after isolation and perfusion of the liver.

Role of Catecholamines in the Control of Newborn Kidney Adenine Nucleotide Content

During the 1st h of extrauterine life, the adenine nucleotide content of the rat kidney is modified: the ATP level increases (+30%) while ADP and AMP are lowered (-30 and -50%, respectively). This leads to a high value of energy charge in the newborn kidney (0.89 vs. 0.80 in the fetus). It was possible to obtain in utero a similar modification of ATP, ADP, AMP concentrations by injections to the fetuses of cAMP, dibutyryl cAMP, or isoprenaline. Conversely, the postnatal changes in adenine nucleotide content could be prevented by administration to the fetus, just before birth, of beta- or beta 1-adrenoreceptor antagonists. Therefore the rise of kidney energy charge following parturition appears to be under hormonal control. Glucagon had no effect on kidney adenine nucleotide content. It is strongly suggested that the catecholamines released at the time of parturition are the triggering factor of this evolution.

Changes in adenine-nucleotide content in the apical bud of Sinapis alba L. during floral transition

The total adenylate pool of the apical buds of vegetative plants of Sinapis alba L. continuously grown in short days fluctuates over a 24-h cycle with the minimum occurring at the end of the dark period. In the buds of plants induced to flower by a single long-day treatment, total adenylate pool increases above the control level 16 h after the start of the long day, resulting mainly from a rise in ATP and ADP contents. This occurs 6 h after the increase in the soluble carbohydrate content previously shown to occur in the apical buds of plants induced to flower (Bodson 1977, Planta 135, 19-23). A transient rise of the energy charge occurs 22 h after the start of the inductive long day.

In vitro alteration of the size of the liver mitochondrial adenine nucleotide pool: Correlation with respiratory functions

Mitochondrial respiration was studied as a function of the total adenine nucleotide content of rat liver mitochondria. The adenine nucleotide content was varied by treating isolated mitochondria with pyrophosphate or by incubating pyrophosphate-treated mitochondria with ATP. Mitochondria with at least 4 nmol adenine nucleotides/mg protein maintained at least 80% of the State 3 activity of control mitochondria, which had approximately 10 nmol/mg protein. However, State 3 decreased rapidly once the adenine nucleotide content fell below 4 nmol/mg protein. Between 2 and 4 nmol adenine nucleotides/mg, State 3 was not limited by the maximal capacity of electron flow as measured by the uncoupled respiration. However, at very low adenine nucleotide levels (<2 nmol/mg), the uncoupled rates of respiration were markedly depressed. State 4 was not affected by changes in the mitochondrial adenine nucleotide content. Adenine translocase activity varied in almost direct correlation with changes in the adenine nucleotide content. Therefore, adenine translocase activity was more sensitive than State 3 to changes in total adenine nucleotides over the range of 4 to 10 nmol/mg protein. The results suggest that (i) State 3 is dependent on the level of intramitochondrial adenine nucleotides, particularly in the range below 4 nmol/mg protein, (ii) adenine translocase activity is not rate-limiting for oxidative phosphorylation in mitochondria with the normal complement of adenine nucleotides, however, at low adenine nucleotide levels, depressed State 3 rates may be explained in part by the low rate of ADP translocation, and (iii) a mechanism of net ATP uptake exists in mitochondria with low internal adenine nucleotides.