ATP and ADP hydrolysis in fish, chicken and rat synaptosomes

Ecto-enzymes capable of hydrolyzing ATP and ADP (NTPDse) are present in the central nervous system of various species. In the present investigation we studied the synaptosomal NTPDase (ATP diphosphohydrolase, apyrase, E.C. 3. 6.1.5) from fish, chicken and rats under different conditions and in the pr esence of several classical inhibitors. The cation concentration required f or maximal activity was 0.5 mM for fish, 1.0 mM for chickens and 1.5 mM for rats with both substrates. The results showed that the pH optimum for all animal preparations was close to 8.0. The temperature used was 25-27 degree sC for fish and 35-37 degreesC for chicken and rat preparations. The inhibi tors azide and fluoride only inhibited the preparation at high concentratio ns (10 mM). Lanthanum (0.1-0.4 mM), N-ethylmaleimide (0.4-3.0 mM) and ouaba in (0.5-3.0 mM) had no effect on NTPDase activity from fish, chickens or ra ts. Orthovanadate (0.1-0.3 mM) only inhibited fish synaptosomal NTPDase. Tr ifluoperazine (0.05-0.2 mM) and suramin (0.03-0.3 mM) inhibited NTPDase at all concentrations tested. Suramin was the most potent compound in causing inhibition, presenting inhibition at 30 muM. Our results demonstrate that t he synaptosomal NTPDase response to several factors is similar in fish, chi ckens and rats, and that the enzyme presents functional homology. (C) 2001 Elsevier Science Inc. All rights reserved.