André Morsch

In vitro effects of l-arginine and guanidino compounds on NTPDase1 and 5′-nucleotidase activities from rat brain synaptosomes

Tissue accumulation of arginine (Arg), N‐acetylarginine (NA), argininic acid (AA) and homoarginine (HA) occurs in hyperargininemia, an inborn error of the urea cycle. In the present study, we investigated the in vitro effects of Arg, NA, AA and HA on NTPDase1 and 5′‐nucleotidase activities from synaptosomal cerebral cortex of rats. The results showed that Arg enhances NTPDase1 activity at the high concentrations tested (1.5 and 3.0 mM) for both the ATP and ADP nucleotides. Activation was also observed with other guanidino compounds tested: NA, AA and HA activated ATP and ADP hydrolysis in all experiments at the concentration of 25 μM. Besides this, NA and AA activated ATP hydrolysis at a lower concentration (1 μM). In another set of experiments, we verified the effect of Arg on purified apyrase at pH 8.0 and 6.5 and observed an increase in the enzyme activity at all Arg concentrations tested (0.01–3.0 mM). In contrast, Arg and the other guanidino compounds tested did not alter 5′‐nucleotidase activity. These results suggest that changes in nucleotide hydrolysis may be involved in the brain dysfunction caused by hyperargininemia amongst other potential pathophysiological mechanisms involved in this condition.

Extrato da casca de Syzygium cumini no controle da glicemia e estresse oxidativo de ratos normais e diabéticos

The plant Syzygium cumini, also known as Black Plum is used widely in the popular medicine for the treatment of diabetes mellitus. This study verified the efficiency of the extract of the bark of Syzygium cumini on the glycemic levels and oxidative stress of normal and diabetic rats induced by alloxan. The animals were divided in control group (C), control treatment group (CT), diabetic control group (DC) and diabetic treatment group (DT). Oral administration of the aqueous extract of the bark of Syzygium cumini, in the dose of 1g/kg live weight, for a period of thirty days, did not result in a significant reduction on glycemia or on glucosilated hemoglobin levels. The treatment with the extract demonstrated an increase in the levels of thiobarbituric acid reactive substances (TBA-RS) in the plasma of the DT group (P <0.05), compared to the C. Kidney catalase activity of rats in DC group decreased significantly (P <0.01) and, in the liver, it showed a significant elevation in group DC (P <0.01). Those results indicated that the extract of Syzygium cumini bark does not possess hypoglycemic effect in alloxan diabetic induced rats. The antioxidant effect of this plant was not enough to reduce the production of TBA-RS significantly. The decrease of catalase activity in the kidneys can be owed to its exhaustion or inhibition, and its increase in the liver could be due to oxidative stress caused by the diabetic status.