Simultaneous determination of etretinate, acitretin and their metabolites in perfusate, perfusate plasma, bile or hepatic tissue with reversed-phase high-performance liquid chromatography.

Etretinate is a synthetic aromatic retinoid used in the treatment of psoriasis and other disorders affecting the skin. Acitretin is the primary active metabolite of etretinate. The in situ perfused rat liver model was used to study the first-pass hepatic metabolism of etretinate and acitretin and a reliable method of quantifying etretinate and its metabolites was needed. Previously published assays allow for the simultaneous quantitation of etretinate and acitretin in blood or plasma. This paper describes an accurate and reliable reversed-phase HPLC method for the determination of etretinate, acitretin and their metabolites in whole perfusate, plasma, bile and hepatic tissue.

Characteristics of the metabolic response of human monocytes to red cells sensitized with anti-D alloantibodies.

In these studies we have characterized the metabolism of the HMPS pathway of PBMs and PMNs from normal persons during interaction with human red cells sensitized with anti-D alloantibody. This was correlated with ADCC as determined by the 51Cr release assay. In this system, the lysis by PBMs of RBCs sensitized with anti-D alloantibodies was mediated by both monocytes and lymphocytes, although the activity of the monocytes was greater. Monocytes, but not lymphocytes, has a burst in HMPS activity during interaction with anti-D-sensitized RBCs. This could be detected with T:E ratios similar to those which caused 51Cr release from the target. Oxygen was required for optimal lysis of antibody-coated RBCs by monocytes, but ADCC was not totally impaired under hypoxic conditions, suggesting that mononuclear cells may have at least two mechanisms for accomplishing ADCC-one that is oxygen-dependent and another that does not involve oxygen radicals. ADCC under aerobic conditions was accompanied by a burst in HMPS activity. In the absence of oxygen there was a 60% reduction in ADCC and no stimulation of the HMPS. However, results of studies for detection of oxygen radicals using standard scavengers during ADCC were negative. In contrast to monocytes, PMNs did not mediate significant ADCC in similar T:E ratios and did not have a metabolic burst when incubated with anti-D-sensitized RBCs. This appears to relate to the low activity of PMNs compared to monocytes in the lysis of RBCs sensitized with anti-D antibody.

A new method for the detection of hydroxyl radical production by phagocytic cells.

Benzoic acid, a specific scavenger of hydroxyl radical (OH.) is known to be oxidized as the result of a reaction with OH.. We have determined that the decarboxylation of benzoic acid can be used to detect OH. generated in cell-free systems and human granulocytes. Benzoic acid is oxidized by the xanthine-xanthine oxidase enzyme system. This system is known to generate O2-, H2O2 and OH.. This oxidation is inhibited by superoxide dismutase, catalase and mannitol. Therefore, the oxidation of benzoic acid occurs by a mechanism similar to that reported for the oxidation of methional to ethylene and involves OH.. Resting granulocytes do not oxidize benzoic acid. However, marked oxidation of this substrate occurs during the phagocytosis of opsonized zymosan particles, indicating the production of OH. by these cells. The reaction can be inhibited by superoxide dismutase, catalase, azide and mannitol. Therefore, the production of OH. in the cell may be similar to that observed in the cell-free system. The granulocytes of a patient with known chronic granulomatous disease did not oxidase benzoic acid, indicating a defect in the generation of OH. by these cells.