FOOD RESTRICTION PROTECTS AND OBESITY INCREASES VULNERABILITY TO ISOPROTERENOL-INDUCED MYOCARDIAL NECROSIS IN RATS

Factors that determine the wide variation in the severity of isoproter enol-induced myocardial necrosis (ISO-MN) are numerous and poorly defi ned. We have investigated the role of age, body weight, food intake, a nd genetic strain differences on vulnerability to ISO-MN in rats. The proportion of apical myocardium that became necrotic after administrat ion of toxic doses of isoproterenol was used as the index of ISO-MN. S prague-Dawrey (SD) rats of 8 to 10 and 16 to 18 weeks of age had 3.4 a nd 3.3 fold more severe apical myocardial lesions respectively than 5- to 6-week-old rats. Among Zucker rats of 8 to 9 weeks of age there wa s 5.2 times more necrosis in obese than in lean animals. Fifty percent food restriction for one week, or 24 hours of fasting in 8- to 10-wee k-old SD rats led to a 50% reduction in the area of necrosis compared to ad lib fed controls. Under similar conditions 16- to 18-week-old ra ts showed a similar reduction with 24-hour fasting, but 50% food restr iction had no effect. Similarly, food restriction had no effect in 5- to 6-week-old SD or obese Zucker rats. Feeding of diets containing lar d, or olive, corn, or fish oils for one week had no significant effect on ISO-MN in SD rats. These results suggests that age, obesity, and f ood intake alter vulnerability to ISO-MN. (C) 1997 by Elsevier Science Inc.