Abstract
[Introduction] It is known that chronic infusion of isoproterenol induces cardiac hypertrophy. The aim of the present study was to characterize left ventricular (LV) function in hypertrophied rat hearts. [Methods] Delivery of drug was achieved by implanting osmotic minipump subcutaneously in the neck of rat. Either isoproterenol (1.2 or 2.4 mg/kg/day for 3 days: Iso 1.2 and Iso 2.4), metoprolol (24 mg/kg/day for 3 days) + Iso 1.2 (Meto+Iso) or vehicle (saline 2.4 ml/kg for 3 days: Sa) was infused subcutaneously. Osmotic minipump was removed three days after the implantation. One hour after removal of the minipump in Sa, Iso 1.2, 2.4 and Meto+Iso groups and two days after removal of the minipump in Iso 1.2 group [ Iso (-) ], we recorded continuous LV pressure-volume (P-V) loops of in situ ejecting hypertrophied rat hearts. Curved LV end-systolic P-V relation (ESPVR) and systolic P-V area at midrange left ventricular volume (PVAmLVV) was obtained from a series of LV P-V loops in Sa and Iso groups. PVAmLVV has been proposed a good mechanoenergetic index to evaluate LV function. [Result] PVAmLVV in Iso 1.2 and Iso 2.4 groups were significantly smaller than that in Sa group. PVAmLVV in Iso (-) group showed the same level as that in Sa group. PVAmLVV in Meto + Iso group was significantly larger than that in Iso 1.2 group. The changes in PVAmLVV in isoproterenol-induced reversible hypertrophied rat hearts, mediated by β1-receptor, precisely reflect the changes in LV work capability even in remodeling rat hearts. [Jpn J Physiol 54 Suppl:S94 (2004)]
