REFEEDING REVERSES CARDIAC MYOSIN SHIFTS INDUCED BY UNDERNUTRITION INAGED RATS - MODULATION BY GROWTH-HORMONE

Growth hormone (GH) was administered (1 mg/day, i.p., 7.5 months) to m ale Fischer 344 rats, in conjunction with refeeding (RF) after chronic undernutrition (UN), from middle age (17 months old) to senescence (2 4.5 months old), during which cardiac myosin heavy chain (MHC) profile s were determined by gel-electrophoresis. At 17 months of age, respect ive MHC-alpha and -beta composition was 74 and 26% in the right ventri cle (RV), and 58 and 42% in the left ventricle (LV), of ad libitum-fed controls, At 24.5 months of age, MHC profiles of controls were shifte d toward the MHC-beta isoform in both RV (alpha = 53%, beta = 47%) and LV (alpha = 40%, beta = 60%), indicating a significant effect of agin g on MHC composition in both ventricles. At 17 months of age, 7.5 mont hs of UN likewise resulted in a shift toward the MHC-beta isoform in b oth RV (alpha = 31%, beta = 63%) and LV (alpha = 22%, beta = 78%) as c ompared to controls, indicating a significant effect of UN in both ven tricles. Continued UN into senescence maintained these, altered profil es in both ventricles, at 24.5 months of age (RV: alpha = 35%, beta = 65%; LV: alpha = 24%, beta = 76%), RF + GH administered from middle ag e into senescence restored the MHC composition in both ventricles (RV: alpha = 57%, beta = 43%; LV: alpha = 43%, beta = 57%), to that of the controls. RF, alone, likewise reversed ventricular MHC composition to ward that of MHC-alpha, but appeared to overcompensate (RV: alpha = 67 %, beta = 33%; LV: alpha = 46%, beta = 54%), surpassing the control an d RF + GH profiles, significantly in the RV. These data suggest that G H is a modulator of restoration of cardiac MHC composition, when RF is administered to counter the effects of chronic UN, in the aging rat h eart. (C) 1998 academic Press