IN-VITRO AND IN-VIVO EFFECTS OF HGCL2 ON SYNAPTOSOMAL ATP-DIPHOSPHOHYDROLASE (EC-3.6.1.5) FROM CEREBRAL-CORTEX OF DEVELOPING RATS

The aim of the present investigation was to evaluate the in vitro (10- 500 mu M) and in vivo (1-21 subcutaneous injections of 2.5 mg/kg each) effects of HgCl2 on the ATP diphosphohydrolase activity (EC 3.6.1.5; apyrase) of synaptosomes from cerebral cortex of rats at different age s (5, 11, 18 and 25 days of life). The in vitro results showed that Hg Cl2 (from 10 to 500 mu M) inhibited the hydrolysis of both substrates by the synaptosomal enzyme at all ages studied. In contrast, HgCI2 inj ected in vivo did no affected the normal ontogeny of ATP and ADP hydro lysis. The hydrolysis of both nucleotides increased at the same rate a s a function of age in control and HgC1(2)-treated rats (the specific activity of enzyme increased about 5-fold from the first week of postn atal life of weaning). The results of the present study demonstrated t hat in vitro HgCl2 inhibited the enzyme, but was ineffective when test ed in vivo. Probably the absence of an in vivo effect is due to the lo w permeability of blood-brain barrier to inorganic forms of mercury.