Bárbara Rücker

Inhibitory avoidance task reveals differences in ectonucleotidase activities between male and female rats.

Studies demonstrated that endogenous levels of estrogen affect the long-term potentiation (LTP) and long-term depression (LTD). ATP and adenosine may play a role in the modulation of LTP. Our laboratory observed in previous studies that inhibitory avoidance task is associated with a decrease in hippocampal ectonucleotidase activities in adult male rats. To explore if ectonucleotidases are modulated in memory formation in female rats, as observed in males, we evaluated the effect of inhibitory avoidance training on synaptosomal NTP Dase and 5′-nucleotidase activities in rat hippocampus from both sexes. The results demonstrated a decrease in ATP, ADP and AMP hydrolysis (37%, 38% and 32%, respectively) immediately after training and a significant inhibition only in ATP hydrolysis (36%) 30 min post-training in male rats. There were no changes in ectonucleotidase activities from female rats. These findings provide support for the view that could exist biochemical differences in ectonucleotidase activities between males and females.

The nucleotide hydrolysis is altered in blood serum of streptozotocin-induced diabetic rats.

Ectonucleotidases and the nucleotide metabolism have been implicated as important regulators of various tissue functions in diabetes disease. Here we evaluated the ectonucleotidase activities and the profile of extracellular ATP metabolism in blood serum of streptozotocin (STZ)-induced diabetic rats. We observed a raise in ATP, ADP, AMP, and 5′-TMP hydrolysis in blood serum after 30 days of diabetes induction, when compared with the citrate group. However, in serum of rats treated 6 days with insulin, the hydrolysis returned to the control levels. Extracellular ATP metabolism estimated by HPLC analysis showed a rapid hydrolysis of extracellular ATP by diabetic animals, leading to the formation of high levels of adenosine when compared with citrate and insulin groups. Since in diabetes the vascular disease is frequently present, the alterations observed are important, because these enzymes control the nucleotides/nucleosides ratio in the circulation and thus the events related to haemostasis.

Repeated stress effects on nociception and on ectonucleotidase activities in spinal cord synaptosomes of female rats

It has been reported that animals submitted to repeated restraint stress present various adaptation responses which are dependent on the sex. These adaptations include changes in nociception and adenine nucleotide hydrolysis. In this study, we report the effect of chronic administration of a gonadal steroid (17beta-estradiol) on ATP, ADP and AMP hydrolysis in spinal cord synaptosomes of adult ovariectomized (OVX) Wistar rats submitted to repeated restraint stress over 40 days. We also measured nociceptive threshold in these animals using the tail-flick test. The results show that tail-flick latencies were decreased in both stressed groups, OVX and OVX rats receiving estradiol replacement therapy, indicating reduced nociceptive threshold after exposure to repeated stress. Repeated restraint stress caused no effect on ATPase or ADPase activities. On the other hand, AMP hydrolysis in spinal cord synaptosomes from repeatedly stressed rats was decreased in OVX rats compared to non-stressed OVX ones, indicating reduced extracellular adenosine production; this effect was reversed by hormonal replacement. These observations suggest that nociceptive sensitivity to noxious stimuli is affected by repeated stress and that modulation of neurotransmission by adenine nucleotides in spinal cord may be altered by the interaction of sexual hormones and psychological factors, such as exposure to stress.

Effects of phenylalanine and phenylpyruvate on ATP-ADP hydrolysis by rat blood serum

Summary. The nucleotide (ATP-ADP)/nucleoside (adenosine) ratio in the circulation can modulate the processes of vasoconstriction, vasodilatation and platelet aggregation. The main objective of the present study with rat blood serum was to evaluate the possibility of changes in nucleotide hydrolysis by phenylalanine (Phe) and phenylpyruvate (PP), the levels of which could increase in the circulation of individuals with phenylketonuria. Results demonstrated that Phe in the range 1.0–5.0 mM inhibited the ADP hydrolysis by rat serum. The effect of inhibition by Phe on ATP hydrolysis appeared only at a concentration of 5.0 mM. PP had no significant effect upon nucleotide hydrolysis. Kinetic analysis indicated that the inhibition of ADP and ATP hydrolysis by Phe in rat blood serum is uncompetitive. Conversely, Phe and PP did not affect the hydrolysis of p-nitrophenyl-5′-TMP by rat serum.

Physical training normalizes nucleotide hydrolysis and biochemical parameters in blood serum from streptozotocin-diabetic rats

Ectonucleotidases and the nucleotide metabolism have been implicated as important regulators in diabetes disease. We evaluated the ectonucleotidase activities and biochemical parameters in blood serum of streptozotocin (STZ)-induced diabetic rats submitted a physical training protocol. We observed a raise in ATP, ADP, AMP and p-Nph-5′-TMP hydrolysis rate and in the levels of cholesterol and triglycerides in rat blood serum, after 30 days of diabetes induction. However, in serum of rats submitted a physical training protocol by forced swimming, both the nucleotide hydrolysis rate and the lipids levels returned to the control values. Considering that diabetes leads to multiple pathophysiological alterations, the modulations observed in ectonucleotidase activities may be part of the events involved in these alterations. Then the physical training is a very important way to control the vascular alterations developed in diabetes.

Ethanolic extract of Casearia sylvestris Sw exhibits in vitro antioxidant and antimicrobial activities and in vivo hypolipidemic effect in rats

The Casearia sylvestris Sw (Flacourtiaceae) is a shrub that occurs in forests of Southern Brazil; its leaves are widely used in folk medicine as a depurative, analgesic, anti-inflammatory and antiulcerogenic agent. The objective of this study was to perform the phytochemical description and to evaluate the pharmacological activities (antimicrobial, antifungal, antioxidant and toxicity) of the ethanolic extract (EE) of C. sylvestris Sw. In addition, we also evaluated the effect of the EE of C. sylvestris Sw on the glucose levels and lipid profile in blood serum of rats submitted to a model of streptozotocin-induced diabetes. Material and Methods: In vitro assay: the detection of chemical groups was done through chemical reactions with the development of color or precipitate and by chromatographic profile; the antioxidant activity was measured by the method of reduction of DPPH free radical (2,2-diphenyl-1- picrylhydrazyl); the Minimum Inhibitory Concentration was evaluated by the broth microdilution method, and the Minimum Bactericide Concentration and the Minimum Fungicide Concentration were performed in Petri dishes; the cytotoxic activity was measured by the Artemia salina test. In vivo assay: diabetic and non-diabetic rats were treated with EE of C. sylvestris Sw (300 mg/ kg) for 45 days, and the glycaemia and lipid profile were analyzed. Results: The EE showed a Lethal Dose50 of 724.76 µg.mL -1 and important antioxidant, fungicide and fungistatic activities. The EE showed better antimicrobial activity regarding the microorganisms Staphylococcus aureus, Escherichia coli and Salmonella setubal. Conclusion: The EE of C. sylvestris Sw produces a significant decrease in triglycerides, total cholesterol and VLDL levels without any significant alteration in the glycaemia. The EE of C. sylvestris Sw presents antioxidant and antimicrobial activities and it exhibits a potent hypolipidemic effect.