Superoxide anion-induced histamine release from rat peritoneal mast cells

We investigated the properties of superoxide anion (O2-)-induced histamine release from rat peritoneal mast cells using superoxide anion radicals obtained from potassium superoxide (KO2). KO2 elicited a rapid histamine release in a dose-dependent fashion, without lactate dehydrogenase (LDH) release. The KO2-induced release was temperature- and energy-dependent. KO2 rapidly increased the intracellular free Ca2+ concentration, accompanied by a marked increase of Ca(2+)-uptake. These findings indicate that the increase in intracellular Ca2+ concentration is involved in the initiation of KO2-induced histamine release, and KO2 could be used as an agent of O2(-)-induced biological reactions.

Effects of glucose and ascorbic acid on absorption and first pass metabolism of isoniazid in rats

We examined the effect of glucose (Glu) and ascorbic acid (AA) on absorption and metabolism of isoniazid (INAH). After p.o. administration of INAH with or without Glu or AA, plasma concentration and urinary excretion of INAH and its metabolites, acetyl INAH (AcINAH), acetyl hydrazine (AcHy) and hydrazine (Hy), were determined by means of gas chromatography-mass spectrometry using stable isotope labeled compounds as internal standard. The combined administration of INAH with Glu or AA led to a significant decrease in the excretion of INAH and Hy, and a significant increase in the excretion of AcINAH and AcHy. The absorption amount of INAH was reduced to about one-half by the addition of Glu and the absorption rate of INAH markedly decreased in the case of co-administration of AA. Comparing the oral case with the results of i.v. administration, Glu and AA only affect the absorption process containing the first pass metabolism of INAH.