[The force-velocity relation and end systolic tension-length relation of hypertrophied myocardium in renal hypertensive rats].

Renovascular hypertension was induced in rats by left renal artery constriction. Force-velocity relation, end systolic tension-length relation (ESTLR) and responses to high extracellular calcium were investigated in hypertrophied myocardium with 4-week hypertension. The results showed that: (1) The myocardial hypertrophy was accompanied by increased peak active tension, decreased maximal velocity of shortening and prolonged contraction duration (P less than 0.01). (2) The ESTLR in hypertrophied myocardium was similar to that in the control, fitted well by an exponential curve and did not show significant alterations in all its regression parameters (P greater than 0.05). (3) No significant difference about the responses to high extracellular calcium (4 mmol/L) was observed between the control and the hypertrophied myocardium (P greater than 0.05). It is concluded that the mechanical properties of hypertrophied myocardium were characterized by a dissociation between force development and velocity of shortening and possibly these contractile abnormalities at the early stage of cardiac hypertrophy are not related to ability of calcium transport in cardiac plasma membrane. The indexes of myocardial mechanics are more sensitive to changes in contractility of hypertrophied myocardium as compared with the parameters of ESTLR.