J. Physiol. (I942) IOI, I3I-I

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1 131 J. Physiol. (I942) IOI, I3I-I THE EFFECT OF SODIUM AND CALCIUM ON THE TOXICITY OF POTASSIUM IN MICE BY C.. W. EMMENS AND H. P. MARKS National Institute for Medical Research, Hampstead, London, N. W. 3 (Received 24 January 1942) TRUSZKOWSKY & DUSZYNSKA [1940] have described the protective effect of desoxycorticosterone acetate against potassium chloride injected intraperitoneally in immature albino mice. In an attempt to repeat their work, we thought it advisable to investigate also the influence of sodium and calcium on potassium tolerance. The beneficial effects of a high intake of sodium chloride in Addison's disease, and in adrenalectomized mammals, suggested that sodium might afford some protection against potassium poisoning, in particular since the work of Zwemer & Truszkowsky [1936], Truszkowsky & Zwemer [1936, 1938] and of Marenzi [1938] tends to show that the symptoms of adrenocortical insufficiency may be due to an excess of potassium. Calcium might be expected to have some influence on the toxicity of potassium in vivo, since it appears to be protective against the action of excess potassium on the isolated mammalian heart. RESULTS Toxicity of potassium chloride Young male albino mice from the Institute's Farm colony were used in all tests, at a body weight of from 13 to 23 g. Preliminary trials showed that the steepest dose/response curve was obtained when, following Truszkowsky & Duszynska [1940], potassium chloride in aqueous solution was given intraperitoneally in direct proportion to body weight. This was supported by the finding that, when all mice in a group were given the same dose of potassium, irrespective of their body weight, those killed were significantly lighter than the survivors (average weight of dead = g., of living = g., diff. = 0*994 g., ud. = g., no. of mice= 100), whereas when the dose of potassium was in porportion to the weight of the mouse, such a difference was never found.

2 132 C. W. EMMENS AND H. P. MARKS TABLE 1. Dose/response data for the toxicity of intraperitoneal KCl in young male albino mice, twenty-five mice per group. All tests were made on the same day. Volume of injections=0-2 ml./10 g. body weight. Dose in mg./10 g. body weight % mortality Table 1 gives data fromh which a regression line for the toxicity of potassium chloride may be calculated; it is sufficient for our immediate purpose to show that the slope of the line is steep (ca. 18) and that the test is thus a sensitive one. The median lethal dose is in this case 6-37 mg. of potassium chloride per 10 g. mouse. Effect of sodium chloride Sodium chloride in doses of 10 and 20 mg./10 g. body weight, given together with the potassium chloride in one injection, proved very effective in protecting the mice from the toxic effects of potassium TABLE 2. The protective effect of NaCl against KCI poisoning, twenty mice per group, intraperitoneal injections. mg. KCl/ Conc. of mg. NaCl/ Conc. of 10 g. body KCI 10 g. body NaCi % Date of test weight % weight % mortality 14. viii viii viii a (Table 2). As the tonicity of the solutions was high, the effect of altering the volume and thus the concentration of the injections was investigated, and shown to be nil. Effect of calcium chloride and of glucose Further simultaneous tests were next made, to determine the effect of calcium chloride given intraperitoneally with potassium chloride, and of glucose solution of high tonicity (approx.= 5/ NaCl or 10% CaCl2) given with the potassium. The results, shown in Table 3, demonstrate the ineffectiveness of both substances, and the ineffectiveness of a merely hypertonic solution.

3 TOXICITY OF POTASSIUM CHLORIDE 133 TABLE 3. The lack of effect of CaCl2 and glucose on the toxicity of KCI injected intraperitoneally, twenty mice per group. All tests were made on the same day. mg. KCl/ Conc. of mg. CaCl2/ Conc. of mg. glucose/ Conc. of 10 g. body KCI 10 g. body CaCl2 10 g. body glucose % weight % weight % weight % mortality 64 3* * * *0 60* Intravenous injections Potassium chloride is more toxic when injected intravenously in mice than when given intraperitoneally, but the response is very much dependent on the rate of injection. We therefore tried to inject at a constant rate, giving the total dose in about 10 sec. Data showing the effects of sodium and calcium chlorides on the toxicity of potassium chloride when injected with it are shown in Table 4. TABLE 4. Effect of NaCl and CaCl2 on the toxicity of KCI when given intravenously in mice. mg. KCl/ mg. NaCl/ 10 g. body 10 g. body weight weight mg. CaCl2/ Conc. of No. (1% (2% 10 g. body CaCl2 of % Date of test solution) solution) weight % mice mortality 2. x * * * *2 2* ' x * * x * * 1.5% solution. It will be seen that sodium is again effective in lowering the toxicity of potassium, and that calcium may possibly have some slight effect in a dose of 1 mg./10 g. body weight, although it is itself toxic in relatively low doses. It seems, however, safest to conclude that these tests by intravenous injection substantiate the results obtained by intraperitoneal injection.

4 134 C. W. EIMMENS AND H. P. MARKS Effect of desoxycorticosterone acetate Although this communication has been written primarily to record the effect of sodium and calcium, it would be misleading to omit mention of the fact that we have not been able to demonstrate any effect with desoxycorticosterone acetate. Thus the work of Truszkowsky & Duszynska, which stimulated the investigation, is not substantiated by our own results. The Polish workers found that 1 mg. of desoxycorticosterone acetate significantly inhibited the response to.potassium, but neither 1 nor 2 mg., administered as they gave it and by several other methods, TABLE 5. The ineffectiveness of desoxycorticosterone acetate on the toxicity of KCI given intraperitoneally to mice. The KCI was injected in a volume of 0-2 ml. water, twenty mice per group. Desoxycorticosterone acetate 1st dose Period (mg.) (sub- 2nd dose before mg. KCI/ cutaneous, (mg.) KCI Date 10 g. body 24 hr., prior (intra- injection % of test weight to KCI) peritoneal) hr. Solvent mortality 12. ix Arachis oil ,, ,, ix Arachis Oil ,, ,, ix Arachis oil Olive oil 90 had any inhibitory influence on the toxicity of potassium in our own mice (Table 5). Indeed, in the tests on 19 September 1941, there was evidence that it actually increased the toxicity, but this was probably due to the very low response to 8 mg. of potassium chloride in the controls. DIsCUSSION A mouse which has been injected intraperitoneally with a lethal dose of potassium chloride dies in a very characteristic manner. For from 5 to 10 min. it shows no symptoms. It then becomes very active, flicking its tail violently and leaping several times into the air, passes into convulsions, and dies with evident respiratory distress. The heart mean-

5 TOXICITY OF POTASSIUM CHLORIDE 135 while continues to beat. Following an intravenous dose of potassium chloride, the mouse may collapse and die almost instantaneously, particularly if the injection is made rapidly, but it exhibits the above series of symptoms when the injection is given more slowly. It does not seem, therefore, that death is due to heart failure, for the symptoms exhibited appear referable to the effects of potassium on the nervous system. This makes the ineffectiveness of the simultaneous administration of calcium more understandable, although it leaves the action of sodium unexplained. The life-saving action of sodium would' seem to fall in line with its effects in adrenocortical deficiency, and perhaps even in shock, since it appears likely that some of the symptoms exhibited in these conditions may be due to a rise in blood potassium. The effectiveness of desoxycorticosterone in the two states mentioned is, however, greater than that of sodium, and it is disturbing that we have obtained negative results with it. SUMMARY 1. The toxicity of potassium chloride when given either intraperitoneally or-intravenously to male albino mice was decreased by the simultaneous administration of sodium chloride, but not of calcium chloride, glucose, or desoxycorticosterone acetate. 2. It is suggested that under the conditions of the tests, potassium kills by an action on the nervous system. The life-saving action of sodium chloride is in line with its beneficial effects in adrenocortical deficiency and in shock, states in which the blood potassium is higher than normal. Our best thanks are due to Dr F. C. MacIntosh for advice and suggestions, Messrs Ciba Ltd., for the supply of desoxycorticosterone acetate. and to REFERENCES Marenzi, A. S. [1938]. Endocrinology, 23, 330. Truszkowsky, R. & Duszynska, J. [1940]. Endocrinology, 27, 117. Truszkowsky, R. & Zwemer, R. L. [1936]. Biochem. J. 30, Truszkowsky, R. & Zwemer, R. L. [1938]. Acta Biol. exp., Varsovie, 12, 1. Zwemer, R. L. & Truszkowsky, R. [1936]. Science, 83, 558.