Biochemical Changes of the Rat Myocardium Induced by Isoproterenol

Abstract

The hearts of rats receiving two subcutaneous injections of 40 rng/kg isoproterenol on consecutive days were analyzed 24 hoa~rs after the second injection t y e t h e r with those of ~o n t r o l rats receiving saline. ?'he myorardial contents of A TP, AH)I', AMP, phosphorylcrerttine, lactate, and pyruvate were determined enzymatically. C';lycogcn, creatil~e, triglyceride, total cholesterol, and phospholipids werc :ilso measured.In fecl as wcll3s in rats starved for 48 hours, the nlyocardirtl A'T13 and creatine coritents were significantly lower in the isoprotereilol-treated rats than in the coratrols. The decrease in XTI' level x a s observed even 48 hours after the last injection. Isoproterenol illjectioris resulted in a n increase i11 pyruvate content a i d a decrease in triglyceride content of the myocardium of fasted rats. Ilowever, the control values of these two substances also differed significantly froin those found in fed controls.The total water content of the heart was higher in the isoproterenol-treated lasted rats. The blood content of the myocardium, on the other hand, was decrerrsed in isoproterenol-treated rats.LliMicnlties involved in proper tissue sampling and handling, together with the importance of the observed changes, are discussed.

Observations on isoprenaline-induced myocardial necroses

“…P. LESZKOVSZKY AND GY. GAL ments by others (Beznhk & Hacker, 1964;Kako, 1965). The results of the quantitative histological evaluation are listed in Table 1.…”

“…The same effect has also been demonstrated in golden hamsters and cats, but not in dogs or domestic pigs (Rosenblum, Wohl & Stein, 1965a). Rats with isoprenaline-induced heart damage have been the subject of several experimental studies (Selye, Veilleux & Grasso, 1960;Wexler & Kittinger, 1963BeznAk & Hacker, 1964;Strubelt & Breining, 1964 ;Kako, 1965). Drugs of different kinds, like thyreostatics (Chappel, Rona & Gaudry, 1959b), monoamine oxidase inhibitors (Zbinden, 1962 ;Zbinden & Bagdon, 1963), /3-adrenergic blocking agents (Ehringer & Gogl, 1963) and, recently, a trinitro-compound (Scriabine & Stebbins, 1966) have all been reported to mitigate the myocardial changes caused by isoprenaline.…”

Effect of Beta-Adrenergic Stimulation on Myocardial Adenine Nucleotide Metabolism

“…Since isoproterenol causes a reduction in myocardial high-energy phosphate stores (16,17) and induces cardiac hypertrophy (18,19), we decided to study its influence on the rate of de novo synthesis of adenine nucleotides in the heart. We used the (S-adrenergic blocking agent propranolol (20) and the "calcium-antagonistic" compound D600 (21,22), which both inhibit the isoproterenol-induced diminution of adenine nucleotide levels, as tools for establishing different cardiac adenine nucleotide levels and elucidating the relationship between the rate of de novo synthesis and the concentration of adenine nucleotides in the myocardium.…”