INVESTIGATING THE RELAXATION, FOLLOWING DIAZO-2 LASER FLASH-PHOTOLYSIS, OF A SKINNED TRABECULAR PREPARATION FROM SHR HYPERTROPHIED LEFT-VENTRICLE

Rat models of cardiac hypertrophy are characterised by a shift in left ventricular myosin isoform from V-1 (adult) to V-3 (foetal), the latt er being associated with a slowing of the acto-myosin ATPase rate. The aim of this study was to examine hypertrophy effects on relaxation by investigating a chemically skinned cardiac preparation from the SHR, where all the cellular membranes are rendered non-functional allowing the myofibrils to be studied in isolation. On comparison, following ph otolysis of the photolabile caged Ca2+ chelator diazo-2, it can be see n that the SHR fibres relax at a slower rate than their age-matched WK Y counterparts. We suggest that, since the thin filament regulatory pr oteins seem not to be affected by cardiac hypertrophy in the rat, this result can be attributed to the shift in left ventricular myosin isof orms. The reduced relaxation rate in the SHR could be the result of a slowing of the dissociation of actin and myosin during the cross-bridg e cycle. These results have previously been published in abstract form [1].