Myocardial dysfunction induced by food restriction is related to morphological damage in normotensive middle-aged rats.
Previous works from our laboratory have revealed that food restriction (FR) promotes discrete myocardial dysfunction in young rats. We examined the effects of FR on cardiac function, in vivo and in vitro, and ultrastructural changes in the heart of middle-aged rats. Twelve-month-old Wistar-Kyoto rats were fed a control (C) or restricted diet (daily intake reduced to 50% of the control group) for 90 days. Cardiac performance was studied by echocardiogram and in isolated left ventricular (LV) papillary muscle by isometric contraction in basal condition, after calcium chloride (5.2 mM) and beta-adrenergic stimulation with isoproterenol (10(-6) M). FR did not change left ventricular function, but increased time to peak tension, and decreased maximum rate of papillary muscle tension development. Inotropic maneuvers promoted similar effects in both groups. Ultrastructural alterations were seen in most FR rat muscle fibers and included, absence and/or disorganization of myofilaments and Z line, hyper-contracted myofibrils, polymorphic and swollen mitochondria with disorganized cristae, and a great quantity of collagen fibrils. In conclusion, cardiac muscle sensitivity to isoproterenol and elevation of extracellular calcium concentration is preserved in middle-aged FR rats. The intrinsic muscle performance depression might be related to morphological damage.
Sugizaki
Mario Mateus
MM
Department of Internal Medicine- School of Medicine, Faculdade de Medicina de Botucatu, UNESP, Rubião Júnior, S/N, 18618-000, Botucatu, SP, Brazil.
Carvalho
Robson Francisco
RF
Aragon
Flavio Ferrari
FF
Padovani
Carlos Roberto
CR
Okoshi
Katashi
K
Okoshi
Marina Politi
MP
Zanati
Silmeia Garcia
SG
Pai-Silva
Maeli Dal
MD
Novelli
Ethel Lourenzi Barbosa
EL
Cicogna
Antonio Carlos
AC
D000375:Aging; D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000378:metabolism; D002122:Calcium Chloride / Q000494:pharmacology; D004452:Echocardiography; D005508:Food Deprivation; D006352:Heart Ventricles / Q000473:pathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron; D009132:Muscles / Q000473:pathology; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology* / Q000648:ultrastructure*; D010210:Papillary Muscles / Q000473:pathology; D051381:Rats; D011921:Rats, Inbred WKY; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D016277:Ventricular Function, Left
D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D002122:Calcium Chloride; D002118:Calcium