Glicemia capilar medida por dois aparelhos de automonitorizaçäo: quanto eles podem estimar a glicemia plasmática na rotina médica? / Capillary blood glucose measurement by tho self-monitoring equipment: how can they to estimate a plasma blood grucose in medical routine?

O desenvolvimento de monitores portáteis para automonitorização da glicose sangüínea tem fácil aceitação pelos pacientes e médicos, sendo amplamente utilizado atualmente, o que torna essencial avaliar o quanto esses resultados correspondem à glicemia plasmática. Assim, avaliamos a acurácia e precisão de dois monitores digitais à disposição no mercado: um utiliza a glicose desidrogenase (Ap1) e o outro a glicose oxigenase (Ap2) na mensuração da glicemia capilar

delta-Aminolevulinate dehydratase inhibition by ascorbic acid is mediated by an oxidation system existing in the hepatic supernatant.

The effect of ascorbic acid (AA) on hepatic delta-aminolevulinic acid dehydratase (ALA-D) activity was studied. AA decreased enzyme activity by reducing maximum velocity and tended to increase the Michaelis constant. ALA-D inactivation by AA occurred similarly both in air and argonium atmosphere incubation. DTT reduced considerably the inhibitory effect of AA on ALA-D, but glutathione was ineffective in reversing inactivation. These data indicate that inhibition occurs mainly due to an acceleration of the oxidation rate mediated by the hepatic supernatant utilizing AA in sulfhydryl groups of cysteine residues present at the ALA-D active site. AA probably acts on cysteine from the ALA-D B site since cucumber and radish leaves ALA-D was not inhibited by AA (up to 16 mM). The addition of free radical scavengers to the medium did not alter ALA-D inactivation caused by AA, indicating that active oxygen species formed during AA oxidation were not directly related to -SH oxidation. The chelation of zinc ions from the enzyme by EDTA turned ALA-D more susceptible to the inhibitory effect of AA. This effect seems to involve mainly ZnB, which is known to bind to four cysteines. The present data suggest that AA may participate in the regulation of the heme biosynthesis pathway by promoting a reversible inactivation of ALA-D.