Effects In Vitro of Guanidinoacetate on Adenine Nucleotide Hydrolysis and Acetylcholinesterase Activity in Tissues from Adult Rats

Abstract

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. The aim of this work was to investigate the in vitro effect of guanidinoacetate in NTPDase, 5'-nucleotidase and acetylcholinesterase activities in the synaptosomes, platelets and blood of rats. The results showed that in synaptosomes the NTPDase and 5'-nucleotidase activities were inhibited significantly in the presence of GAA at concentrations of 50, 100, 150 and 200 microM (P < 0.05). However, in platelets GAA at the same concentrations caused a significant increase in the activities of these two enzymes (P < 0.05). In relation to the acetylcholinesterase activity, GAA caused a significant inhibition in the activity of this enzyme in blood at concentrations of 150 and 200 microM (P < 0.05), but did not alter the acetylcholinesterase activity in synaptosomes from the cerebral cortex. Our results suggest that alterations caused by GAA in the activities of these enzymes may contribute to the understanding of the neurological dysfunction of GAMT-deficient patients.

NTPDase and 5′-nucleotidase activities in synaptosomes of rabbits experimentally infected with BoHV-5

“…The ectonucleotidase activities were determined using a protocol previously described (Heymann et al 1984;Spanevello et al 2008;Jaques et al 2011;Gutierres et al 2012;Becker et al 2013). The NTPDase activity was performed in a medium (200 μl) with pH 8.0 and potassium chloride (5 mM), calcium chloride (1.5 mM), ethylenediaminetetraacetic acid (0.1 mM), glucose (10 mM), sucrose (225 mM), and Trishydrochloride (45 mM).…”

“…The NTPDase activity was performed in a medium (200 μl) with pH 8.0 and potassium chloride (5 mM), calcium chloride (1.5 mM), ethylenediaminetetraacetic acid (0.1 mM), glucose (10 mM), sucrose (225 mM), and Trishydrochloride (45 mM). The 5′-nucleotidase activity was accessed in a medium (200 μl) with pH 7.5 and magnesium sulfate (10 mM) and Tris-hydrochloride (100 mM) (Heymann et al 1984;Spanevello et al 2008). To the reaction solution was added 20 μl of sample (synaptosomes: 8-12 μg of protein) and incubated at 37°C for 10 .…”

“…Then, the tubes were cooled for 10 min. Malachite green (colorimetric reagent) and monopotassium phosphate (standard) were used to determinate the release of inorganic phosphate (Pi) (Chan et al 1986;Spanevello et al 2008). All samples were run in triplicate.…”