Reduction in cortisol inactivation is part of the adrenal stress response to cardiac and noncardiac pediatric surgery: a prospective study using gas chromatography-mass spectrometry analysis.

We examined the hypothesis that major cardiac surgery triggers a more intense adrenal stress response than less intensive noncardiac surgery, which then alters cortisol inactivation. Urinary excretion rates of glucocorticoid metabolites were determined before and after surgery using gas chromatography-mass spectrometry in 29 children undergoing scheduled major cardiac surgery and 17 control children undergoing conventional noncardiac surgery in a prospective observational study. Excretion rates of glucocorticoid metabolites were summed and corrected for creatinine excretion to calculate cortisol production rates (mg/mmol creatinine/m(2) body surface area). Precursor/product ratios from individual metabolites were calculated to characterize cortisol inactivation (11ß-hydroxysteroid dehydrogenase). Postoperatively, median cortisol production rates increased in both groups ( MCS: from 2.7 to 9.3; controls: from 2.7 to 5.8; p<0.001) with no significant difference between groups (p=0.12). Ratios of cortisol to cortisone metabolites, indicating the overall activity of 11ß-hydroxysteroid dehydrogenase, increased postoperatively in both groups (p<0.001). In conclusion, surgery resulted in a distinct postoperative increase in cortisol production. In contrast to our hypothesis, children undergoing major cardiac surgery did not show an increased adrenal stress response compared to children undergoing conventional surgery. Furthermore, the reduction in cortisol inactivation appears to be an essential part of the stress response to pediatric surgery in general.

Immunopharmacodynamic studies of cyclosporine in patients awaiting renal transplantation.

The immunopharmacodynamics of cyclosporine were investigated in eight hemodialysis patients awaiting renal transplantation. Cyclosporine was administered orally (10 mg/kg) and intravenously (4 mg/kg), with both administrations separated by at least one week. Plasma samples were processed at 37 degrees C and analyzed for specific cyclosporine and its four major metabolites (AM1, AM1c, AM9, and AM4N) using high-performance liquid chromatography. In addition, the in vitro immunosuppressive activity of these serial plasma samples was estimated as a relative percentage inhibition of third party mitogenic lymphocyte proliferation stimulated with phytohemagglutinin. The relationships between concentration and effect of cyclosporine versus time were noted. These results suggest that unchanged cyclosporine concentrations in plasma correlate with mitogen-induced lymphocyte suppression yielding significant immunosuppressant activity of cyclosporine. Control studies with plasma from healthy volunteers spiked with cyclosporine in the concentration range of 0-10,000 ng/mL were developed. A sigmoidal Emax model was fitted to the effect versus plasma concentration data. The ratio of effect versus predicted effect were calculated for intravenous cyclosporine dosing. There was a good correlation between the observed and predicted inhibitory effect.

Cellular cytotoxicity mediated by isotype-switch variants of a monoclonal antibody to human neuroblastoma.

The biological property of an antibody is determined by its antigen binding characteristics and its isotype-related effector functions. We have established monoclonal antibodies of different isotypes by stepwise selection and cloning of the hybridoma CE7. The original CE7 secretes an IgG1/kappa (CE7 gamma 1) antibody that recognises a 185 kD cell surface glycoprotein expressed on all human sympatho-adrenomedullary cells. Isotype-switch variants were isolated in the following sequence: from the original CE7 gamma 1, CE7 gamma 2b variants were isolated, and from a CE7 gamma 2b variant CE7 gamma 2a variants were isolated. The antibodies of three different isotype variant cell lines possess identical antigen binding characteristics, but display distinct effector functions as demonstrated by antibody dependent cell-mediated cytotoxicity (ADCC). ADCC was performed with the neuroblastoma line IMR-32 as the target cells, and different FcR gamma positive cells were either freshly isolated from human peripheral blood leukocytes or cultured for 6-10 days and tested as potential effector cells. Tumour lysis mediated by monocyte-derived macrophages depended on the presence of CE7 gamma 2a antibodies; antibodies from the CE7 hybridomas of gamma 2b and gamma 1 isotypes were virtually inactive in ADCC assay. Pre-exposure of macrophages to rIFN-gamma enhanced their ADCC activity, a result that is compatible with the notion that the high affinity Fc IgG receptor (FcR gamma I/CD64) is involved in the triggering of ADCC in macrophages. In contrast to macrophages, mononuclear cells, nonadherent cells and monocytes displayed considerable non-specific lytic activity, which was little influenced by the presence of antibody regardless of the isotype added.