Enhanced formation of ethane and n-pentane by rat hepatocytes in the presence of dimethyl sulfoxide.

Incubation of rat hepatocytes with 14 mM dimethyl sulfoxide (DMSO) produced an increase in the formation of ethane, measured by capillary column gas chromatography, to 18.0 pmoles/hr/10(7) cells from 11.2 pmoles/hr/1-(7) cells from 5.6 pmoles/hr/10(7) cells in control hepatocytes. This was about one-third the stimulation of ethane and n-pentane formation produced by incubation of hepatocytes with 13 mM carbon tetrachloride. DMSO-stimulated ethane and n-pentane formation was inhibited up to 63% by 0.1 microM alpha-tocopherol and up to 89% by N2. Formation of dimethylsulfide from DMSO by hepatocytes was the same in air and N2. DMSO increased methane production by hepatocytes to 31.3 pmoles/hr/10(7) cells from 6.9 pmoles/hr/10(7) cells in control hepatocytes. Although DMSO apparently stimulated lipid peroxidation by hepatocytes, as measured by ethane and n-pentane formation, there was no increase in the formation of thiobarbituric acid reactive material. DMSO was not toxic to hepatocytes, measured by release of cytosolic lactate dehydrogenase, over a 2-hr incubation. Possible mechanisms for the increase in alkane formation by DMSO are discussed.

Disposition of tricyclic nucleoside-5'-monophosphate in blood and plasma of patients during phase I and II clinical trials.

Tricyclic nucleoside-5'-monophosphate (TCN-P) and its dephosphorylated metabolite tricyclic nucleoside (TCN) have been measured in the blood and plasma of patients receiving TCN-P by rapid iv infusion in a phase I trial at daily doses of 24-55 mg/m2 for 5 days and in patients receiving TCN-P in a phase II trial at a single dose of 250 mg/m2. TCN-P was rapidly accumulated by rbcs and had an initial half-life in blood of 6.1 hours and a terminal half-life of 89.2 hours. Total-body blood clearance of TCN-P was 2.6 ml/minute/m2. The concentration of TCN-P in blood was not related to the dose of TCN-P and did not increase over 5 days' administration in the phase I patients. Plasma contained little detectable TCN-P even 5 minutes after administration. Plasma contained low concentrations of TCN, up to 0.4 microgram/ml, which were maintained over several days. TCN did not accumulate in the plasma with repeated administration of TCN-P in the phase I patients. No other metabolites of TCN-P, apart from TCN, were detected in blood or plasma. No relationship was detected between pharmacokinetics and toxic response of TCN-P in the phase II patients.