Résumé : Prolonged exposure to high concentrations of human recombinant interleukin-1 beta (rIL-1 beta) has been reported to exert both suppressive and cytotoxic effects on pancreatic beta-cells during culture in vitro. In order to investigate the molecular mechanism(s) underlying the actions of rIL-1 beta on the beta-cell, we have exposed isolated rat pancreatic islets for 3 or for 24 h to 25 U/ml of rIL-1 beta. Subsequently the biosynthesis of heat shock proteins, as assessed by western blot analysis, and total protein biosynthesis patterns were studied, using one and two-dimensional gel electrophoresis of [35S]methionine labelled islet proteins from different subcellular compartments. It was found that rIL-1 beta exerted no specific effects on protein synthesis when added during a 3 h incubation period. However, after a 24 h incubation period, the synthesis of a group of acidic proteins with the approximate molecular weight of 35 kD was specifically inhibited in the rIL-1 beta treated islets. This alteration was predominantly associated with the endoplasmic reticulum fraction. The cytokine also inhibited the synthesis of four cytosolic proteins with the molecular weights 75, 85, 95 and 120 kD. In contrast, rIL-1 beta increased the expression of the heat shock protein hsp70 both in the microsomal and cytosolic fractions, in contrast to the islet nuclei in which no increase was found. These results show that exposure of pancreatic islets to rIL-1 beta is accompanied by specific alterations in the protein synthesis of the islet cells.(ABSTRACT TRUNCATED AT 250 WORDS)