David Lehr

CLINICAL TOXICITY OF SULFONAMIDES

More than two decades have elapsed since Gerhard Domagk’s epochal discovery that, to quote him in translation: “Prontosil enables the mouse infected with streptococci to live if it is treated subcutaneously or orally with the drug within 24 hours of the beginning of the infection.”l After a slow and little-noticed beginning of successful human application in Germany, spearheaded by the pioneering work of scientists in many other countries, such as the TrCfouels et aZ.* in France, Colebrook and Kenny3 and Buttle et aZ.4 in England, and Long and Bliss,5 Marshall et al.,‘j and others in the United States, sulfonamide therapy gained rapid and widespread acceptance throughout the world. The startling and world-shaking realization that now, for the first time in history, systemic bacterial infections could be treated specifically by the administration of chemical compounds, because these substances lacked prohibitive toxicity to the tissues of the host, resulted in a veritable flood of experimental and clinical publications. So thorough and so extensive were these reports (among others7-13), that a comprehensive picture of the entire range of clinical toxicity became available within a relatively short time after the introduction of each new sulfonamide compound. For example, in the excellent paper of Van Dyke,I4 presented fourteen years ago, we find little to be modified or to be added to the lucid description of the signs and symptoms of clinical toxicity. However, while the type and character of toxic reactions have not changed materially from those encountered in the early years of sulfonamide therapy, their incidence has shown a remarkable decline with the decrease in the use of the older and more toxic compounds, with the introduction of better tolerated sulfonamide derivatives of lower over-all toxicity, and with the development of a number of highly effective safety measures. This dramatic drop in the occurrence of potentially dangerous toxic reactions, particularly in renal complications, sensitization reactions, and blood dyscrasias was, in fact, one of the primary reasons for the amazing resurgence of sulfonamide therapy in recent years, which is the more significant since it occurred in the era of antibiotics.

Continued pharmacologic analysis of consummatory behavior in the albino rat

Abstract In continuation of the pharmacological analysis of consummatory behavior in the albino rat, it was established that the mechanisms of the response to peripherally injected serotonin, namely copious drinking and simultaneous inhibition of the urine flow, is closely related to that of the β-adrenergic agonist isoproterenol. In 23-hr food deprived rats, peripheral serotonin (1.0 mg/kg, s.c.) like isoproterenol (0.1 mg/kg, s.c.), caused a more than 50% inhibition of the one hour food intake, which like the drinking was obviated by propranolol and enhanced by tolazoline. In contrast, the almost equipotent anorexic effect of peripheral d-amphetamine (0.5 mg/kg, s.c.) remained unaltered by the same α- and β-adrenergic blockade. Direct application to the perifornical hypothalamus of isoproterenol (30 μg) or serotonin (18 μg) elicited highly significant inhibition of the food intake, which was likewise obviated by central pretreatment with propranolol and enhanced by tolazoline. The close similarity of effects upon eating behavior obtained with the peripheral and central route of administration are interpreted as evidence for the existence of β-adrenergically coded satiety circuits. The central dipsogenic activity of angiotensin II was inhibited by pretreatment of the intracerebral site with tolazoline but not by phenoxybenzamine, phentolamine, propranolol or atropine, whereas chlorpromazine produced exaggeration of water intake. Peripheral administration of atropine (5 mg/kg, s.c.), on the other hand, dramatically reduced the intracerebral dipsogenic activity of angiotensin II, whereas methylatropine was without effect, suggesting that cholinergically coded circuits are involved in the mediation of angiotensin-induced drinking. Since peripheral atropine (5 mg/kg, s.c.) had no effect on drinking elicited by peripheral isoproterenol, it is concluded that angiotensin does not constitute the final mediator in the brain of thirst evoked by systemic β-adrenergic activation.

TISSUE ELECTROLYTE ALTERATION IN DISSEMINATED MYOCARDIAL NECROSIS

An entire section of this monograph is devoted exclusively to myocardial injury induced by sympathomimetic amines. It seems pertinent, therefore, to explain that omission of this specific identification from the title of my presentation was deliberate and intended to emphasize that the myocardial changes to be described are not limited to damage induced by adrenergic amines, but appear to be a characteristic and perhaps stereotyped expression of cellular injury. There is little doubt that tissue response to an injurious stimulus may be as uniform and as specific as that to physiological activation. Thus, cardiac muscle, for instance, which contracts in the same way, irrespective of the nature of the eliciting stimulus, apparently responds to a great variety of noxious agents with the development of disseminated necrosis and mononuclear cell infiltration. This point was emphasized by Dr. Wartman in his opening remarks to this monograph; he stated that there are only a few possible morphological reactions to injury, and since there are numerous injurious agents, many will cause the same morphological changes. Drs. Laufer and Davis put it even more succinctly when they said that the myocardium may be damaged in many ways, but reacts in very few. The findings to be reported in this paper will demonstrate that the similarity is not limited to the morphological appearance of the injury, but probably encompasses a number of other parameters. In fact, it would seem that the morphological changes are the late expression of a series of characteristic metabolic alterations inherent in cell degeneration which may participate in the initiation of irreversible failure of cell function. It was with this concept in mind that my associates and I became interested several years ago in the significance of shifts of the tissue electrolyte content which accompany the development of disseminated myocardial necrosis induced by a variety of unrelated procedures. We wanted to know, in particular, whether some of these electrolyte shifts contribute to the causation of myocardial injury or whether all such derangements are solely the consequence of necrosis. In favor of a causative influence of electrolyte imbalance, one may cite the fact that cardiac necrosis can be induced by dietary deficiency of potassium or magnesium, and that the severity of this injury can be enhanced by sodium loading and by mineralocorticoids and inhibited by the administration of magnesium and potassium chloride. Against a causative role of electrolyte derangements, on the other hand, one may cite the well-documented findings that necrotic tissue invariably manifests substantial deviations of the electrolyte content. It will be demonstrated in this paper that similar sequential alterations of the myocardial electrolyte pattern accompany the evolution and healing of disseminated myocardial necrosis from unrelated noxae. The observations to be

Inhibition of Drug Precipitation in the Urinary Tract by the Use of Sulfonamide Mixtures. I. Sulfathiazole-Sulfadiazine Mixture.

Summary It was observed that N1-heterocyclic derivatives of sulfanilamide, even if closely related, are soluble in one and the same solution almost to the extent of their separate solubilities. Based on this observation, the toxicity and antibacterial activity of sulfadiazine-sulfathiazole mixtures was investigated. It was found that the acute and chronic toxicity of this drug combination for albino rats is strikingly low if compared with the effect of similar or identical total concentrations of either sulfathiazole or sulfadiazine alone. Evidence derived from chemical analyses and post-mortem examinations pointed to a diminution of intrarenal obstruction from drug precipitate as the chief reason for the low toxicity of the mixture. In vitro antibacterial studies showed that the effectiveness of the mixture corresponded largely to the total concentration of free sulfonamide. On the basis of these observations, the substitution at the bedside of sulfathiazole or sulfadiazine by combinations of these two compounds was suggested, because their application might decrease the danger of renal complications without interfering with the antibacterial efficacy. Clinical trials are in progress.

CAUSATIVE RELATIONSHIPS OF PARATHYROID HORMONE TO RENOGENIC AND RENIPRIVAL CARDIOVACULAR DISEASE

I t is generally recognized that hyperactivity of the parathyroid glands leads to demineralization of the skeleton and may result in the deposition of calcium salts in the renal tubules, in the myocardium, in the arterial tree, in the stomach wall, and in other soft-tissue sites.’ This laying down of lime salts is widely believed to take place in healthy tissue as a consequence of the simple physical phenomenon of precipitation from a supersaturated solution. I t is distinguished by the term “true metastatic calcification” from “dystrophic calcification,” which designates the encrustation of necrotic tissue debris with calcium salts?, Hyperparathyroidism has also been implicated as a cause of hypertension,‘ and a vasoactive factor has been described in parathyroid hormone.‘, However, since the kidneys are invariably damaged in this situation, whether as a result of excess parathyroid hormone (primary hyperparathyroidism) or as the original stimulus for its overproduction (secondary hyperparathyroidism), it is difficult to distinguish the contribution of renal impairment to the hypertensive mechanism from a possible participation of the parathyroid hormone. In the course of studies on the prevention of renal sulfonamide injury in albino rats, my interest in the parathyroid gland was aroused by the combination of severe nephrocalcinosis, massive calcification of the aorta and its ramifications, and distinct hypertrophy of the parathyroid In exploring this lead with improved procedures for the production of experimental arteriosclerosis by renal injury,8-’0 it was found in our laboratory that extensive disseminated necrosis in the myocardium, in the arterial media, and in the muscularis of the gut invariably preceded demonstrable deposition of calcium. Subsequently it was shown that the development of muscular necrosis and its sequelae could be readily prevented by prior thyroparathyroidectomy.” Studies directed toward elucidation of the mechanism underlying the striking protective effect of thyroparathyroidectomy (TPx) led to the conclusion that the cardiovascular and smooth muscle injury was dependent upon the presence of excess parathyroid hormone.12 On further analysis it was demonstrated that hyperfunction of the parathyroid gland resulted from the breakdown of renal function rather than from a toxic substance released by the damaged kidney; it could therefore be induced by bilateral nephrectomy as readily as by severe renal injury. I t was also established that, under both these conditions, adrenal cortical hormones were of importance in triggering or permitting the release of excess parathyroid hor-

Effect of cardiotoxic doses of adrenergic amines on myocardial cyclic AMP

Abstract The role of beta-adrenergic activation in the cardiotoxicity of adrenergic amines was assessed by measuring rat myocardial cyclic AMP at various times after subcutaneous injection of necrosis-inducing amounts of isoproterenol, phenylephrine or epinephrine in the presence and in the absence of the phosphodiesterase inhibitor aminophylline. The β-adrenergic agonist isoproterenol (5.25 mg/kg) increased myocardial cyclic AMP at 1 h to 147% of control and in the presence of aminophylline (75 mg/kg) to 261% of control as compared to 146% for aminophylline alone. Propranolol (6.25 mg/kg) blocked isoproterenol-induced increases in cyclic AMP. Neither the α-adrenergic agonist phenylephrine (15 mg/kg) nor epinephrine (4 mg/kg), which has both α- and β-adrenergic properties, increased myocardial cyclic AMP above control levels even in the presence of aminophylline. With α-adrenergic blockade by tolazoline (15 mg/kg) or phenoxybenzamine (2 mg/kg), combined administration of epinephrine and aminophylline caused an increase of the myocardial cyclic AMP content to 163% and 173%, respectively, of that of control rats. These results suggest that in the intact rat, cyclic AMP-mediated myocardial stimulation is an important factor in the cardiotoxicity of isoproterenol but not of phenylephrine, while the beta-adrenergic component of epinephrine cardiotoxicity is unmasked only in the presence of α-adrenergic blockade.

Pathogenesis of Experimental Arteriosclerosis in the Rat.

Summary 1. Pathogenesis of severe arteriosclerosis and disseminated myocardial necrosis, induced in the albino rat by standard renal injury, was investigated. These cardiovascular lesions are due to autointoxication with parathyroid hormone, and this hormone apparently contains an important hypertensive factor. 2. Evidence was presented that excess production of parathyroid hormone, as a consequence of renal dysfunctions, is mediated through the adrenal cortex and that mineralocorticoids are essential for direct or indirect activation of the parathyroid gland. To some degree, androgens can enhance the mineralocorticoid effect, whereas estrogens seem to inhibit emergence of muscular necrosis. The incidence of cardiovascular injury in intact and adrenalectomized rats was found to be substantially higher in male than in female animals. 3. It was shown further that, in the absence of parathyroid glands, mineralocorticoids in excessive dosage fail to produce cardiovascular necrosis, whereas excess parathyroid hormone assures emergence of typical lesions in complete absence of mineralocorticoids. In fact, by providing abundant supplies of parathyroid extract, cardiovascular necrosis was induced without renal injury and even in absence of kidneys. 4. Implications of these findings upon the concept of “metastatic calcification” and upon pathogenesis and therapy of renogenic cardiovascular necrosis and hypertension in human beings are discussed. It is suggested that subtotal parathyroidectomy be tried in preference to adrenalectomy in attempts to arrest rapidly progressive sequellae of malignant hypertension.

Time course of development and cessation of myocardial sensitization to isoproterenol by DCA-saline in the albino rat the role of protein synthesis

Abstract The time course the development of myocardial sensitization to isoproterenol induced by desoxycorticosterone acetate (DCA) was determined in albino rats implanted subcutaneously with various doses of DCA and maintained on 1% saline as drinking fluid. The animals were challenged at predetermined intervals following DCA implantation with a single, subcutaneous dose of isoproterenol (150 ug/kg body weight). The onset of myocardial sensitization, as determined by the incidence of mortality (due to ventricular fibrillation) was not dependent on the dose of DCA used and was noted within one or two days from the beginning of exposure to DCA. Removal of the steroid pellet after 6 days of pretreatment resulted in rapid decline of sensitization. Removal of DCA after 33 or 90 days of pretreatment, on the other hand, did not completely abolish sensitization. Treatment with the protein synthesis inhibitors cycloheximide and actinomycin D prevented the development of myocardial sensitization.

Enhanced Incidence of Isoproterenol-Induced Ventricular Fibrillation in the Magnesium-Deficient Rat

The electrocardiogram was recorded and serum and bulk myocardial electrolytes were determined in male Sprague Dawley rats, subjected to dietary magnesium deficiency for various periods, to assess the time course of development and cessation of the enhanced arrhythmogenic action of isoproterenol (150 micrograms/kg, subcutaneously) and to establish possible relationships between electrolyte changes and severe ventricular dysrhythmias. Ventricular fibrillation occurred within 60 min following isoproterenol injection in 25, 25, 62.5, 50, and 62.5% of rats on magnesium deficient diet for 4, 7, 11, 15, and 19 days (N = 8), respectively, and resulted in death in most animals (83%). Reintroduction of normal chow following a 30-day period on magnesium-deficient diet normalized serum magnesium (from 1.42 +/- 0.23 to 1.90 +/- 0.08 mEq/liter, mean +/- SD) but did not significantly reduce the incidence of ventricular fibrillation. Magnesium deficiency did not produce statistically significant alterations in bulk myocardial content of sodium, potassium, magnesium, and calcium. However, sodium was elevated and potassium diminished in hearts from rats that died in ventricular fibrillation, but not in those that had recovered. Magnesium-deficient rats sacrificed 30 min after isoproterenol injection, that is before the occurrence of ventricular fibrillation, exhibited hypomagnesemia and hypokalemia as well as elevated sodium and diminished potassium and magnesium in the myocardium. In contrast, rats on Purina Chow exhibited hypermagnesemia, but also showed hypokalemia and diminished cardiac potassium. The results indicate that magnesium deficiency enhances the arrhythmogenic propensity of isoproterenol and that the development of ventricular fibrillation is preceded by serum and myocardial electrolyte alterations.

Enhanced Arrhythmogenic Activity of β-Adrenoceptor Stimulants in Desoxycorticosterone-Pretreated Rats

The arrhythmogenic activity of four beta-adrenoceptor stimulants, metaproterenol, salbutamol, isoetharine, and dobutamine, was determined in adult, Wistar rats pretreated for 3-4 weeks with desoxycorticosterone (DOCA) and 1% saline as drinking fluid. Doses (SC) of these stimulants which were well tolerated in untreated animals elicited severe ventricular dysrhythmias, often leading to death in ventricular fibrillation. The LD50 in mg/kg was as follows: metaproterenol, 0.28; salbutamol, 0.60; isoetharine, 2.3; and dobutamine, 4.8. The relative potency of metaproterenol, salbutamol, and isoetharine correlates well with their ability to stimulate beta 1-adrenoceptors. It is suggested that DOCA-saline pretreatment in rats may be used as a model for the rapid screening of drugs affecting beta-adrenoceptors.