Beta-endorphin levels after intrathecal infusion of iodinated contrast media

Modifications in beta-endorphin levels in cerebrospinal fluid have been described following lumbar puncture and metrizamide injection. Cerebrospinal fluid (CSF) samples were obtained from 19 patients before and after lumbar myelography. Two radioimmunoassays were used. One was a commercial kit; and the other one (developed in our laboratory) used a chromatographic removal from beta-lipotrophin. No definite variation of beta-endorphin was observed after myelography, using either the commercial kit or a more sophisticated procedure. Some controls were prepared by adding metrizamide or Iopamidol in vitro to CSF samples in order to evaluate a non specific effect of these contrast media. The results obtained with these controls suggest that the discrepancy of results may be explained simply by assay artifacts due to drug interferences when using the commercial methods.