MICRODIALYSIS IN THE ESTIMATION OF INTERSTITIAL MYOCARDIAL NEUROPEPTIDE-Y RELEASE

The purpose of this study was to investigate the feasibility of cardia c microdialysis for the in vivo estimation of cardiac interstitial pep tide concentrations, and, to determine the changes in neuropeptide Y r elease in myocardial tissue during experimental brain death in pigs. U sing a specifically designed concentric flexible probe, perfused with Ringer solution containing 0. 5 % of bovine serum albumin at a flow ra te of 2 mul/min, allowed us to obtain a 23 +/- 2 % relative recovery r ate in vitro. Based on these in vitro recovery data, a regional study of the kinetics of interstitial NPY levels following brain death was o btained by monitoring the changes in NPY dialysate levels recorded fro m dialysis probes implanted into the right and left ventricular walls of the beating heart in vivo. Basal dialysate NPY levels determined by radioimmunoassay were of 95.2 +/- 7.0 and 93.2 +/- 9.1 pmol/l in left and right ventricle, respectively. Brain death was followed by a sust ained 2 h increase in NPY dialysate levels in both ventricles (peak le vels: 173.2 +/- 30.9 pmol/l in left ventricle, and 149.7 +/- 23.9 pmol /l in right ventricle), which then returned to control levels. We conc lude that cardiac microdialysis is a simple and promising new tool for evaluating the role of peptides in cardiovascular regulation.