title: Food restriction impairs myocardial inotropic response to calcium and beta-adrenergic stimulation in spontaneously hypertensive rats.
abstract: Although long-term food restriction (FR) has been shown to induce cardiac remodeling and dysfunction, there are few data on the effects of FR on pressure-overloaded hearts. The aim of this study was to examine the effects of FR on cardiac muscle performance during inotropic stimulation in the myocardium of spontaneously hypertensive rats (SHRs). Male 60-day-old SHRs were subjected to FR for 90 days. Food-restricted animals received 50% of the ad libitum amount of food consumed by the control group. Myocardial function was studied in isolated left ventricular papillary muscle under isometric contraction in basal condition (1.25 mmol/L extracellular Ca(2+) concentration) and after 3 inotropic maneuvers: (1) at postrest contraction of 30 seconds, (2) at extracellular Ca(2+) concentration of 5.2 mmol/L, and (3) after beta-adrenergic stimulation with 10(-6) mol/L isoproterenol. At basal condition, time from peak tension to 50% relaxation was greater in the food-restricted group (P < .05). Inotropic stimulation with postrest contraction and isoproterenol promoted a significant lower increase of developed tension, maximum rate of tension development, and maximum rate of tension decline in the food-restricted compared to the control group. The elevation of extracellular Ca(2+) concentration induced a lower increase of developed tension, maximum rate of tension development, and time from peak tension to 50% relaxation in the food-restricted than in the control group. In conclusion, long-term FR promotes impairment of myocardial inotropic response to calcium and beta-adrenergic stimulation in SHRs.
authors.affiliation: Department of Internal Medicine, School of Medicine, State University Júlio Mesquita Filho (UNESP), Botucatu, São Paulo, Brazil.
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Gut
authors.forename: Mario Mateus
authors.initials: MM
authors.lastname: Sugizaki
authors.forename: Marina Politi
authors.initials: MP
authors.lastname: Okoshi
authors.forename: Robson Francisco
authors.initials: RF
authors.lastname: Carvalho
authors.forename: Maeli Dal
authors.initials: MD
authors.lastname: Pai-Silva
authors.forename: Flavio Ferrari
authors.initials: FF
authors.lastname: Aragon
authors.forename: Carlos Roberto
authors.initials: CR
authors.lastname: Padovani
authors.forename: Katashi
authors.initials: K
authors.lastname: Okoshi
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Cicogna
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000494:pharmacology; D005508:Food Deprivation / Q000502:physiology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000473:pathology; D010210:Papillary Muscles / Q000187:drug effects; D010805:Physical Conditioning, Animal; D011897:Random Allocation; D051381:Rats; D011918:Rats, Inbred SHR
chemical_list: D000318:Adrenergic beta-Agonists; D002316:Cardiotonic Agents; D002118:Calcium