Joseph T. Judd

Myocardial necrosis induced by isoproterenol in rats. Changes in serum protein, lipoprotein, lipids and glucose druing active necrosis and repair in arteriosclerotic and nonarteriosclerotic animals.

From The May Institute for Medical Research, Jewish Hospital and Departments of Pathology and Biological Chemistry, University of Cincinnati College of Medicine, Cincinnati, Ohio. Supported by grants from the Southwestern Ohio Heart Association and by Grants HE-8868, HE-8813 and HE-6315 from the National Heart Institute and a General Research Support Grant (FR-5633), United States Public Health Service. * Research Career Program Award (HE-K3-1734) from the National Heart Institute, United States Public Health Service. t This work was performed during the tenure of an Advanced Research Fellowship from the American Heart Association. Present address: Oregon Regional Primate Center, Beaverton, Oregon. In previous reports we have described various pathophysiologic changes which occur in nonarteriosclerotic virgin rats and arteriosclerotic breeder rats during the acute onset and repair of myocardial necrosis.I-3 The nonarteriosclerotic virgin rats display a much more severe reaction to the stress of drug-induced cardiac necrosis than the breeder rats with pre-existing arteriosclerosis. In addition to a greater mortality rate, nonarteriosclerotic rats also show much greater cha,nges in their serum glutamic acid transaminases, both oxalopyruvic and pyruvic (SGOT and SGPT) and lactic dehydrogenase (LDH) levels during the acute onset and repair of myocardial necrosis.3 Analyses in vitro of the aketolic adrenal steroid production patterns of animals undergoing cardiac destruction and repair also demonstrated marked differences in the steroid patterns between nonarteriosclerotic and arteriosclerotic rats.2 The adrenocortical steroidogenic patterns and the gravimetric and histopathologic changes in the adrenal and thymus glands of these animals indicated that there is an intense

Myocardial Connective Tissue Metabolism in Response to Injury: HISTOLOGICAL AND CHEMICAL STUDIES OF MUCOPOLYSACCHARIDE AND COLLAGEN IN RAT HEARTS AFTER ISOPROTERENOL-INDUCED INFARCTION

Arteriosclerotic and nonarteriosclerotic rats were given isoproterenol sufficient to cause massive myocardial injury. Hearts, livers, and kidneys were taken for analysis of the connective tissues at various intervals. Mucopolysaccharide was identified as Hale-positive material digestible with testicular hyaluronidase. Hexosamine and hydroxyproline were determined by chemical means. The changes in the connective tissue following infarction were divided into two phases. The first, occurring 1 to 2 days after the induction of necrosis, was characterized by extensive edema, accumulation of hexosamine, and by histologically demonstrable mucopolysaccharide. The second phase, 3 to 7 days after infarction, was characterized by changes typical of wound healing in general, involving both mucopolysaccharide and collagen deposition in foci of myocardial scar tissue formation. The increase in hexosamine was the same in arteriosclerotic breeder animals, which required one-half the dose of isoproterenol, as in virgin animals receiving the full dose of isoproterenol. Since the dose was selected to produce relatively the same degree of necrosis in each type of animal, it was thought that the increase in hexosamine was directly related to the injury and not to the isoproterenol per se. No comparable increase in hexosamine was observed in either the liver or kidney.

Responses to Drug-Induced Myocardial Necrosis in Rats with Various Degrees of Arteriosclerosis

Severe myocardial necrosis was produced in virgin Sprague-Dawley rats without preexisting arteriosclerosis and in breeder Sprague-Dawley rats with various degrees of arteriosclerosis by giving two subcutaneous injections of isoproterenol; the virgin rats received 50 mg/100 g and the breeder rats 25 mg/100 g body weight. Breeder rats withstood the stress and shock of myocardial necrosis with fewer untoward effects than the virgin animals. Changes in the thymus and adrenal glands also indicated that the arteriosclerotic breeder rats responded with a different pattern of adrenocortical activity. There were marked differences between the nonarteriosclerotic and arteriosclerotic rats in the fluctuation of serum transaminases and lactic dehydrogenase levels during the stress of myocardial necrosis. During the acute stages of myocardial necrosis there was intense activation of lipid metabolism with gross and microscopic evidence of intense fatty infiltration of the liver; during myocardial repair this lipid was removed concomitantly with reduction of hypercholesteremia. The dichotomy of response has been ascribed to the possibility that the preexisting arteriosclerosis in the breeder rats led to the development of increased collateral coronary artery circulation which afforded some degree of protection to the myocardium.

The role of lactation and weaning in the pathogenesis of arteriosclerosis in female breeder rats

Summary Female breeder rats develop spontaneous arteriosclerosis if they are actively and repeatedly bred. Females which nursed large litters following each pregnancy appeared to develop the most severe arterial disease as well as other degenerative changes. In order to determine how the degree of lactational activity would affect the pathogenesis of the arterial disease female breeder rats were provided with many, few or no pups during the lactation phase following each of 4 pregnancies. To test the effect of abrupt cessation of milk removal vs . complete removal of milk, breeder females were provided with many pups to nurse following each of 4 pregnancies. However, in some cases the young were removed suddenly, i.e. , forced weaning, after 23 days of lactation, whereas some females were permitted to nurse their young until they gave up nursing voluntarily, i.e. , natural weaning. A special group of breeders completed 1 pregnancy only but was provided with nursing pups for an extended period of time, i.e. , 100 days. The results of these experiments demonstrated, that female breeders which had experienced one or several pregnancies and which had lactated actively followed by abrupt weaning of the young developed grossly visible arteriosclerosis characterized by severe calcific complications. On the other hand, breeders which were permitted to suckle their young until they were weaned naturally were completely free of the severe calcific arterial involvement. However, early microscopic intimal mucopolysaccharide accumulations capped by collagen could be found in all breeders. These intimal lesions are believed to be the forerunners of the more complicated lesions and are believed to be associated with the gestational phase of the reproductive cycle.

Arterial lesions in repeatedly bred spontaneously hypertensive rats.

Repeatedly bred male and female rats of many strains develop hyperglycemia, hyperlipidemia, hypertension, and arteriosclerosis spontaneously. The intensity of their arterial disease and related metabolic derangements appears to be related to their reproductive activity. Repeatedly bred spontaneously hypertensive rats (SHR) were found to have severe hypertension, hyperglycemia, hyperlipidemia, elevated creatine phosphokinase (CPK), serum glu-tamic oxaloacetic and glutamic pyruvic transaminase (SGOT, SGPT), and lactic dehydrogenase (LDH), as well as high circulating corticosterone levels. Despite these atherogenic metabolic derangements and their severe hypertension, the breeder SHR did not develop the severe, generalized arteriosclerosis found in other strains of breeder rats. Instead, the arterial lesions, consisting of intimal hyalinization and fibrosis, medial hypertrophy, and occlusion of the lumen, were found only in male breeder SHR and were confined to the intratubular arteries of the testes. It is suggested that the severe hypertension, genetic influences, or differences in hypothalamic-pituitary-adrenal-gonadal function in breeder SHR may not have been conducive to the development of arteriosclerosis in this particular strain of rats.

Changes in calcium, hydroxyproline and mucopolysaccharides in various aortic segments of arteriosclerotic breeder rats

Summary The calcium and hydroxyproline content of rat aortae has been determined chemically in both arteriosclerotic breeder rats and non-arteriosclerotic virgin rats. In the case of male breeders with microscopic arteriosclerosis, the calcium content of the aorta was essentially the same as that found in virgin male rats. Very little difference was found in hydroxyproline content in male virgin and breeder aortae. However, a substantial difference was found in both calcium and hydroxyproline content of female virgin aortae and female breeder aortae. The difference in calcium and hydroxyproline between male and female breeders has been associated with the more severe arteriosclerosis found in the female breeder. The concentration of calcium was found to be greatest in the upper portions of the aorta and to decrease in the more distal portions. Calcium concentration increased with ascending degrees of arteriosclerosis in the carotid, arch, thoracic and abdominal segments of the aorta. The hydroxyproline concentration decreased with ascending degrees of arteriosclerosis. Histologically, these same aortae also showed subintimal accumulation of mucopolysaccharides which became transformed into fibrous tissue. Little or no lipid was found in these lesions. Medial mucopolysaccharides showed increasing concentration with ascending degrees of arteriosclerosis. Hemorrhage, ulceration, elastosis and aneurysm formation were all associated with alterations in the mucopolysaccharides of the ground substance. The state of mineralization of the aorta, as represented by the calcium content and the availability of collagen, as represented by the hydroxyproline determinations, indicate that the dystrophic calcification, elastosis, cartilaginous metaplasia and bone formation in these animals is probably related to the observed biochemical changes in calcium and collagen.

Variations in Response to Severe Alloxan Diabetes in Arteriosclerotic and Nonarteriosclerotic Rats

Repeatedly-bred rats develop arteriosclerosis, hyperlipidemia, hyperglycemia and other degenerative changes, spontaneously. An injection of alloxan (10 mg./100 gm. body weight, subcutaneously, eighteen-hours postfasting) given to healthy, virgin and to arteriosclerotic and diabetic breeder rats caused severe ketosis, hyperglycemia, hyperlipidemia and fatty metamorphosis of the liver. Animals were sacrificed daily for one week and after the fourth and eighth week of severe, untreated diabetes. The previously arteriosclerotic rats showed the greater catabolic and pathophysiologic changes. Many animals died on the third day postalloxan with massive fatty metamorphosis of the liver. At this time, adrenal and thymus gland weights, serum enzymes, e.g., SGOT, SGPT and LDH, serum lipids, e.g., free fatty acids, triglycerides and cholesterol, serum corticosterone and urinary 17-ketosteroids, as well as chemical analyses of hepatic lipids, e.g., total lipids, trigly- ceride and cholesterol, all reflected the severe insulin deficiency. Eventually, the severity of these pathophysiologic changes subsided. Approximately half of the animals became emaciated with milky serum containing high levels of glucose and lipids. These animals were ketotic, their beta cells were agranular and they were severely arteriosclerotic. Remaining animals were “obese,” with fatty livers but normal-appearing serum containing less glucose and lipid than their emaciated counterparts. These “obese” diabetic rats had less severe ketosis, partially degranulated beta cells and regression of their arteriosclerosis. This dichotomous response to severe diabetes may be due to the partial recovery of beta cells of some animals concomitant with partial correction of defective lipid and carbohydrate metabolism.

Comparative effects of adrenal regeneration hypertension on non-arteriosclerotic and arteriosclerotic Sprague-Dawley VS spontaneously hypertensive rats☆

Adrenal regeneration hypertension (ARH) was induced in virgin and breeder, spontaneously hypertensive (SHR) and Sprague-Dawley (SD) rats. The blood pressure of the previously normotensive, virgin, SD rats and the SD breeder rats with preexistent mild hypertension became greatly elevated. ARH caused an increase in the preexisted severe hypertension in SHR virgin and breeder rats. Serum enzymes, e.g., CPK, SGOT and LDH, were greatly elevated concomitant with the finding of old and new foci of myocardial necrosis. ARH produced a dichotomous metabolic effect, i.e., elevated cholesterol, glucose, and corticosterone levels in SD rats but reduced levels in SHR rats. The zonae glomerulosae of the the regenerated adrenal glands of SD rats were devoid of lipid whereas the zonae glomerulosae of SHR rats were full of lipid. Intact SHR breeder rats develop arterial lesions confined to their reproductive organs but after ARH treatment, they were found to have aortic, coronary and renal arterial lesions which were similar to those which occur, spontaneously, in SD breeder rats. It is suggested that changes in the spectrum of adrenal steroids produced during ARH may contribute to the diverse metabolic changes and the alterations in the usual cardiovascular degenerative changes found in these two strains.

Acute Changes in Liver Lipids during Myocardial Infarction Induced by Isoproterenol

Summary Adult, male Long-Evans rats were challenged with two subcutaneous doses of the potent catecholamine, isoproterenol. Within hours after the first injection myocardial ischemia and necrosis became apparent. On the second day, after the second injection, myocardial necrosis reached a zenith followed by myocardial repair during days 4–7 after the initial injection. During the development of myocardial ischemia and necrosis there is dramatic loss of body weight; dissolution of periadrenal, mesenteric, and other adipose tissue depots; hyperlipidemia; and grossly-visible fatty metamorphosis of the liver. During the myocardial repair phase the hyperlipidemia and the condition of fatty liver disappear rapidly. Chemical analysis of the hepatic lipid fractions demonstrate that there is a very considerable and rapid increase in hepatic triglycerides, a less marked and less rapid but significant increase in hepatic cholesterol, and only a modest fluctuation in hepatic phospholipid.

Hexosamine and β-glucuronidase alterations during the acute onset and repair of isopreterenol-induced myocardial infarction

Abstract This investigation demonstrates that isoproterenol-induced myocardial infarction in Long-Evans rats is characterized by alterations in serum and myocardial hexosamine and β-glucuronidase during acute myocardial ischemia or necrosis. With the ebb of active cardiac necrosis, in those animals which survive, myocardial hexosamine becomes reduced and the activity of myocardial β-glucuronidase becomes significantly increased concomitant with the appearance and subsequent formation of myocardial scar tissue and repair. Since β-glucuronidase is involved in the catabolism of mucopolysaccharides it is believed that the changes in these two myocardial constituents, hexosamine and β-glucuronidase, are indicative of a dynamic process pertaining to myocardial wound repair.