1994 Volume 35 Issue 3 Pages 333-343
Isolated papillary muscles have often been used in myocardial mechanical function studies. The objective of the present study was to compare the mechanical function of papillary muscle isolated from left ventricle between Wistar (W) and Wistar-Kyoto (WKY) rats of different ages (1, 3, 6 and 12 months), in order to examine whether there is a difference in intrinsic mechanical properties of muscle between the two rat strains. Muscles were perfused with Krebs-Henseleit solution at 28°C and studied isometrically and isotonically at a stimulation rate of 0.2Hz. The W and WKY showed statistically significant differences during both isometric and isotonic contractions. During isometric contraction, (1) the peak developed tension (DT) and +dT/dt were lower in WKY rats in the 1mo groups, (2) the resting tension (RT) was greater in WKY at 3, 6 and 12mo, (3) time to peak tension (TPT) was greater in WKY at 3 and 12mo, (4) time for tension to fall from peak to 50% of peak tension RT 1/2) was greater in WKY at 3mo and (5)-dT/dt was lower in WKY at 1 and 3mo. During isotonic contraction, (1) the peak shortening (PS) and -dL/dt were lower in WKY at 12mo, (2) the time to peak shortening (TPS) was greater in WKY at 3 and 12mo; (3) +dL/dt was lower in WKY at 3, 6, and 12mo and (4) the relative variation of length (Lmax-PS)/Lmax was greater in WKY at 6 and 12mo. These data showed a difference in mechanical behaviour of the papillary muscle between Wistar and Wistar-Kyoto rats of different age.
