Effect of contrast media on beta-endorphin secretion. An in vitro study

The central nervous system may be highly susceptible to the toxic effects of contrast media (CM). Previous experiments demonstrated that vasopressin is released after the intravenous administration of CM. The present study examined the response of the opiocortin system to CM. Neurons of the rat basal hypothalamus, dispersed and attached to Cytodex-3 beads, were perfused with sodium diatrizoate, metrizamide or iohexol (3 mg iodine/ml). The effluent was collected, and the beta-endorphin (B-E) content was measured by a radioimmunoassay technique. Results, normalized to the internal positive control, were compared with release from normal saline (negative control) by analysis of variance. Diatrizoate and metrizamide caused significant release of B-E (p less than 0.03). Iohexol did not stimulate release of B-E. These results suggest that diatrizoate and metrizamide, but not iohexol, can stimulate the release of hormones from hypothalamic neurons. The phenomenon may play a role in some reactions to intravascular CM administration since these neurons are not protected by a blood-brain barrier.