MECHANISM OF POLYAMINE TOXICITY IN CULTURED CARDIAC MYOCYTES

The goal of this study was to investigate the mechanism of polyamine-m ediated injury to the cardiac myocytes isolated from neonatal rat hear ts. The myocytes, cultured in Dulbecco's minimal essential medium-1% f oetal calf serum (FBS), were exposed to spermidine or spermine. The to xicity to myocytes was determined by (a) increased release of creatine kinase (CPK) into the media and (b) decline in cell viability or func tional activity. Spermidine, above 10 mu M, increased the release of C PK into media, decreased cell viability and decreased the functional a ctivity of the myocytes. The FBS exhibited polyamine oxidase activity and semicarbazide-sensitive amine oxidase activity. Aminoguanidine, MD L72,527 or semicarbazide, are the inhibitors of amine oxidases, polyam ine oxidase (PAO) and semicarbazide-sensitive amine oxidase (SSAO), re spectively. The addition of these inhibitors to the medium protected t he myocytes from spermidine toxicity. To determine whether myocyte PAO is involved in polyamine toxicity, we used horse serum that contained high SSAO activity and negligible PAO activity. The myocyte extracts had negligible SSAO activity but high PAO activity; When myocytes:were cultured in horse serum in lieu of FBS, spermine caused toxicity at a bove 100 mu M. In horse serum, MDL72,527 and semicarbazide protected t he myocytes from spermine toxicity. These observations show that extra cellular amine oxidases and myocyte PAO are significant in mediation o f polyamine toxicity. (C) 1998 Elsevier Science Ltd. All rights reserv ed.