RESUMEN

Streptosotocin-induced diabetes in rats is accompanied by the development of diabetic complications such as neuropathies. [2-14C]serotonin and [U-14C]GABA release from the neurotransmitter pre-loaded synaptosomes showed significant elevation. Aldose reductase inhibitors (AL-1576, sorbinil) administration leads to partial restoration of serotonin and GABA release, while picamilon restored only GABA release. It was shown that Na+,K(+)-ATPase activities decreased in synaptosomes, synaptic membranes and sciatic nerve of diabetic rats compared to control. Administration of AL-1576 normalized Na+, K(+)-ATPase activity, while sorbinil and picamilon less effectively. Sorbitol level are increased in streptozotocin-diabetic rats as compared to control. The picamilon and aldose reductase inhibitors administration to diabetic rats is accompanied by the partial reduction of brain sorbitol level. The findings confirm the important role of picamilon and aldose reductase inhibitors in the prevention and treatment of diabetic neuropathy.

Asunto(s)

RESUMEN

Diazepam-binding inhibitor isolated from synaptic membranes exerts a pronounced inhibitory effect on the specific benzodiazepine-receptor binding of 3H-flunitrazepam and simultaneously leads to an increase of synaptosomal uptake of 14C-GAMA. At the same time the inhibitor also depresses the specific binding of 14C-NAD by synaptic membranes, but displaying a greater effect. In both cases the inhibition was competent. Whether the isolated neuropeptide may act as an intermediary in the interaction with the reception system of NAD with GABA-benzodiazepine-receptor complex.

Asunto(s)

RESUMEN

Participation of nicotinic acid and its derivates in the functioning of nervous system is considered basing on the data from literature. It is supposed that the favourable therapeutic effects of nicotinamide, nicotinic acid and their active biological form--NAD are realized due to the mechanisms of their functioning in the nervous system, for treating schizophrenia, epilepsy and other diseases of the nervous system.

Asunto(s)

RESUMEN

Studies of neurotransmitter uptake and release by isolated rats brain cortex synaptosomes demonstrated that [2-14C]serotonin uptake was by 41% lower in streptozotocin-diabetic rats as compared to control. The [U-14C]GABA uptake was considerably elevated. [2-14C]serotonin and [U-14C]GABA release from the neurotransmitter pre-loaded synaptosomes showed significant elevation, especially during the first 3 minutes. Nicotinamide (NAm) administration (200 mg/kg body weight daily, 14 days) to diabetic rats restored synaptosomal serotonin uptake up to control levels, while the GABA uptake tended to decrease in diabetic rats. With this dose of NAm the partial restoration of serotonin and GABA release was achieved. The modulating effect of in vivo administered NAm acts via NAD which binds specifically with synaptic membranes. It has been shown that brain NAD(P)/NAD(P)H decreased while sorbitol level increased in streptozotocin-diabetic rats as compared to control. The NAm administration to diabetic rats is accompanied by the increase of NAD(P)/NAD(P)H and the reduction of brain sorbitol level. Data obtained confirm the important role of NAm in the pathogenesis of diabetic encephalopathies.

Asunto(s)

RESUMEN

Bicucculine being introduced to rats has induced an increase of [14C]GABA capture with synaptosomes and simultaneous decrease of GABA and NAD level in the brain. The decrease of the inhibiting effect of GABA is accompanied by the increase of specific binding of [3H]flunitrazepam with benzodiazepine receptors at the expense of the increase of binding capacity from 0.33 to 0.45 g/mol per 100 mg of protein. Under these conditions the dissociation constant remains unchanged. Such an activation of benzodiazepine receptors was observed under the lack of NAD in the organism (model of PP-hypovitaminosis). Introduction of the surplus doses of nicotinamide neutralizes the convulsant effect on benzodiazepine receptors.

Asunto(s)

RESUMEN

Administration of corazol into animals led to a decrease in content of NAD and gamma-aminobutyric acid (GABA) in brain. Under these conditions, binding of 14C-GABA was increased and its liberation was inhibited in the synaptosomes of the brain cortex. Additional administration of nicotinamide, accompanied by considerable increase in content of NAD and GABA, caused a decrease in accumulation of exogenous GABA in the synaptosomes and removed the effects produced by the convulsant agent. Kinetics of 14C-GABA binding in the presence of NAD demonstrated that the more effective inhibition of the binding occurred in the animals treated with the convulsant drug. NAD appears to affect the GABA-ergic transmission at the postsynaptic level.

Asunto(s)

RESUMEN

NAD has been studied for its effect on the uptake of serotonin, norepinephrine, dopamine and GABA by synaptic vesicles. It has been shown that norepinephrine and dopamine uptake is not altered by addition of 10(-3) M, 10(-6) M, 10(-8) M, 10(-9) M and 10(-12) M NAD concentrations to incubation medium while the serotonin uptake is increased by 29, 47, 23, 24 and 18%, respectively. 10(-3) M and 10(-6) M NAD concentrations decrease GABA uptake by 30% and 24%. The study of 10(-6) M NAD effect on serotonin release from serotonin pre-loaded vesicles demonstrated the marked elevation of the neurotransmitter release, especially during the first 4 minutes of incubation (by 40%). The similar effect on serotonin release, is observed after addition of KCl, standard depolarizing agent, to the incubation medium. In contrast to synaptic membranes, the red blood cell membranes did not activate the neurotransmitter release after addition of serotonin pre-loaded vesicles to incubation medium, which proves the specificity of synaptic vesicles--synaptic membranes interaction. The modulating NAD action at the presynaptic membrane level can also be assumed.

Asunto(s)

RESUMEN

After administration of corazole content of gamma-aminobutyric acid (GABA) was increased in the rat brain within 2 min and 10 min by 28% and 80%, respectively. Content of the GABA was distinctly decreased in the prespastic phase. During this period specific binding of 3H-muscimol to the GABA receptors was decreased. NAD at concentrations 10(-6) M and 10(-7) M activated the GABA receptors and inhibited binding of 14C-GABA to the synaptosomes of both intact rats and the animals treated with the convulsant agent. NAD appears to cause an effect as an inhibitory neurotransmitter at the postsynaptic level.

Asunto(s)

RESUMEN

A decrease of the NAD and serotonin level in the brain of rats with PP hypovitaminosis is shown. NAD in concentration of 10(-6) M in vitro exerts a less pronounced inhibiting influence on the neuronal uptake of [14C]serotonin and [14C]GABA by brain synaptosomes of rats with PP hypovitaminosis. GABA content under such conditions increases as compared with the control and correlates with changes in the [14C]GABA uptake system.

Asunto(s)

Asunto(s)

RESUMEN

Content of nicotinamide nucleotides, reception of NAD by synaptic membranes and the system of 14C-serotonin uptake and liberation in rat brain nerve endings were studied under various conditions of vitamin PP consumption. In PP hypovitaminosis binding of 14C-NAD was decreased in synaptic membranes as a result of alterations in capacity of receptor sites, which occurred simultaneously with low level of nicotinamide coenzymes in rat brain. These alterations led to deterioration of NAD modulating function in liberation of 14C-serotonin from synaptosomes. The data obtained suggest that functional activity of NAD-receptor system in synaptic membranes of rat brain depends on the rate of vitamin PP consumption. These results might be considered in clinical research when vitamin PP is used for treatment of various diseases.

Asunto(s)

RESUMEN

The receptor protein solubilized from synaptic membranes specifically binds [14C] NAD (dissociation constant--0.75 microM, capacity of binding sites--0.0125 nmol of metaid per 1 mg of protein). All the studied benzodiazepines (phenazepam, nitrazepam, clonazepam, flunitrazepam) are able to displace [14C] NAD from its receptor sites, the mixed type of inhibition being manifested. An inhibition constant for flunitrazepam, a ligand of benzodiazepine receptors, equals 10 microM. GABA promotes an inhibiting effect of benzodiazepines. It is supposed that neurotropic action of NAD is realized through the GABA-benzodiazepine complex of neuronal membranes.

Asunto(s)

RESUMEN

The NAD-binding receptor protein has been solubilized from the synaptic membranes of the rat brain by different detergents. Digitanin proved to be the most effective detergent which exerted no action on the specific binding of [14C]NAD with the solubilized receptor protein. Kinetic parameters of the soluble ligand-receptor complex were studied. The affinity of the solubilized receptor protein to NAD did not change as compared to the protein of native membranes. The specific binding of [14C]NAD was saturated at Kd = 0.53 microM, Bmax = 0.011 nmol per 1 mg of protein. The molecular weight of the soluble NAD-receptor complex determined under native conditions was equal to 115 kDa.

Asunto(s)

RESUMEN

The binding of [14C]NAD to rat brain synaptic membranes is reversible and depends on incubation time, temperature and protein concentration in the reaction mixture. The value of the rate constant for [14C]NAD binding to the synaptic membranes at 24 degrees C (kl) is 1.1 X 10(-6) M-1 S-1, the rate constant for dissociation of the [14C]NAD-receptor complex (k-1) is 3.3 X 10(-3) S-1. The value of the constant for the ligand dissociation from this complex (Kd) is 3.0 nmole. Treatment of the experimental results in the Scatchard plots for the equilibrium binding of [14C]NAD to the synaptic membranes demonstrated that the receptor sites with high and low affinities for the ligand (Kd1 = 3.3 nmol, Kd2 = 14.4 nmole) and with binding capacities of 44 and 77 pmole of [14C]NAD, respectively. It was found that the synaptosomal membrane components which bind the labelled NAD have a protein nature. Data from [14C]NAD and [nicotinamide-3H]NAD binding suggest that brain synaptic membranes bind NAD at the nicotinamide and adenylic moieties.

Asunto(s)

RESUMEN

The paper deals with a regulatory effect of the redox state of nicotinamide coenzymes on glyceroneogenesis in the epididymal fatty tissues involving incorporation of [2-14C] pyruvate into synthetized de novo blood glucose, glycerol and fatty acids of triacyglycerines. Large values of the NAD+/NADH and NADP+/NADPH ratios in cytoplasm and mitochondria promote a high rate of lipogenesis and glucose oxidation processes, which is pronounced in a more intense 14C incorporation into fatty acids than in triacylglycerol glycerols. A decrease in the NAD+/NADH ratio and an increase in the reducing ability of NAD-pairs under fasting intensify glyceroneogenesis in the fatty tissue. The incorporation of [14C] pyruvate into blood glucose in 3.6 times as high, the radioactivity of fatty acids lowers. Nicotinamide administered to animals after fastening inhibits glyceroneogenesis in the fatty tissue, lowering considerably the incorporation of [14C] pyruvate into triacylglycerol glycerol and blood glucose.

Asunto(s)

RESUMEN

The paper deals with the redox state of free nicotinamide adenine dinucleotides (the NAD+/NADH ratio) in main compartments of the rat and guinea pig liver cells. NAD-pairs of cytoplasm and mitochondria in guinea pigs liver are shown to be more reduced than those in rats' liver. Stimulation of glucogenesis decreases the NAD+/NADH ratio in both compartments of rat liver and increases it in the guinea pigs' liver mitochondria. The guinea pigs' liver mitochondria synthesize actively phosphoenol pyruvate from oxaloacetate, malate and alpha-ketoglutarate. A decrease in the NAD+/NADH ratio value with introduction of beta-oxybutyrate into the incubation medium inhibits the phosphenolpyruvate synthesis from malate by 73%.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

Experimentally-induced alloxan diabetes was characterized in rats by a marked increase in the blood glucose level and by a number of disturbances in the concentration of metabolites and the activity of the enzymes of carbohydrate metabolism in the liver. Stimulation of gluconeogenesis in diabetes was judged by reduction of the redox condition of free NAD- and NADP-couples, by the increase in the concentration of phosphoenolpyruvate, malic oxaloacetate and phosphoenolpyruvate carboxykinase activity of the liver. Nicotinamide in a dose of 50 mg per 100 g of body weight caused a marked reduction in the blood glucose level of diabetic rats. An increase of the [NAD+]/[NADN], [NADP+]/[NADPN] ratio, a reduction of the concentration of phosphoenolpyruvate, malate and phosphoenolpyruvate carboxylase activity pointed to the inhibition of gluconeogenesis and stimulation of glycolysis in the liver of diabetic rats given nicotinamide.

Asunto(s)

RESUMEN

An intensified synthesis of glucose is observed in gluconeogenesis from endogenous precursor only for the first 30 min of perfusion. Pyruvate introduction into the medium raises phosphoenolpyruvate carboxykinase and fructose-1,6-diphosphatase activities in the liver and determines maintenance of the glucose formation high rate for 90 min of perfusion. 1,3-butanediol is found to have a stimulating effect on gluconeogenesis from pyruvate. Introduction of 1,3 bytanediol into perfusate decreases the redox state of free NAD-pairs, increases the content of phosphoenolpyruvate, malate. ATP and the phosphoenolpyruvate carboxykinase and fructose-1.6-diphosphatase activity in the perfused liver.

Asunto(s)