The effect of lathyrogen beta-amino proprionitrile (BAPN) on the mechanical properties of experimentally hypertrophied rat cardiac muscle.

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Abstract
BAPN at dietary concentrations of 1, 5 and 10 g BAPN/kg rat chow was administered to rats for 14-21 days following surgical constriction of the ascending aorta. At 5 and 10 g BAPN/kg rat chow prevented the increase in left ventricular collagen content which occurred with cardiac hypertrophy in rats following aortic constriction. In spite of this block in the increase in collagen in the ventricles, isolated trabecular muscles from hypertrophied hearts showed a decrease in max of shortening at a preload of 0.5 g/mm2 (Vmax) and an increase in time to peak tension as compared with values for sham-operated animals. Vmax for rats with aortic constriction was decreased 0.57 muscle length/as compared with sham-operated animals (P < 0.01) but time to a peak tension was prolonged by 12 m (P < 0.05). In rats with aortic constriction receiving 10 g BAPN/kg rat chow Vmax was decreased 0.66 muscle length/s (P < 0.05), and time to peak tension was prolonged by 21 ms (P < 0.001). Resting tension was increased to 1.70 .+-. 0.18 (mean .+-. SEM) [Standard error of the mean] g/mm2 as compared with shams (1.22 .+-. 0.10 g/mm2; P < 0.002) in cardiac hypertrophy without BAPN. The increase in resting tension was not seen when animals with aortic constriction received 10 g BAPN/kg rat chow [1.23 .+-. 0.9 g/mm2 as compared with shams, 1.15 .+-. 0.09 g/mm2 (not significant)]. The decrease in Vmax of shortening and prolongation of time to peak tension in experimental cardiac hypertrophy occur independently of elevated collagen content but elevations in resting tension apparently depend on an increase in collagen content of these hearts.