SINCE the glucose excreted by the fasted depancreatised dog must, in

THE EFFECT OF SHIVERING ON THE RESPIRATORY QUOTIENT IN PANCREATIC DIABETES. By I. L. CHAIKOFF and J. J. R. MACLEOD. From the Department of Physiology, University of Toronto, Canada. (Received for publication 7th January 1929.) SINCE the glucose excreted by the fasted depancreatised dog must, in part at least, be derived from fat (cf. MACLEOD, 1928), an R.Q. of about 7 can no longer be regarded as proof that fat is being directly oxidised by the diabetic organism. If it were so, then the R.Q. should not rise when combustion is increased, as during muscular exercise. HETZEL and LONG (1926) found that the R.Q. of the excess metabolism of an eight-minute period of exercise in a diabetic patient from whom insulin had been withheld for twenty to thirty hours was 86, but the result is inconclusive, since part of the islet tissue of the pancreas, even in severe forms of the disease, must still be functioning, so that high quotients might be ascribed to oxidation of carbohydrate stored in the liver because of the presence of insulin in the organism. The present investigation was therefore undertaken with the view of obtaining evidence as to whether muscular activity would cause the quotient to rise when no insulin was present in the body, as must be the case in depancreatised dogs. The most satisfactory way to perform the experiment, no doubt, would be to have a treadmill within the respiratory cabinet, but, since this was not available, we have studied the effect of the milder degree of muscular hyperactivity which can be induced by shivering. Although this only caused the oxygen consumption to increase about twofold over the resting value, a definite rise in R.Q. occurred in most of the experiments. METHODS. Following complete removal of the pancreas, the dogs were injected twice daily with insulin and were fed with raw meat, raw pancreas, and cane sugar. When the wounds had completely healed and the animals were in good nutritional condition, food and insulin were discontinued for a few days, after which the respiratory metabolism of the resting animal was determined. This was repeated on the following day, while the animal was shivering as a result of subjecting it to a cold bath

292 Chaikoff and Macleod prior to putting it into the respiratory cabinet, which also was cooled down by circulating cold water in its walls so that the temperature of the inside air was between 1 C. and 13 C. A similar procedure was adopted for normal fasted dogs. The respiratory apparatus employed was that described elsewhere (1), and the observed R.Q. of the alcohol controls, which were frequently run, corresponded satisfactorily with the theoretical. The carbondioxide capacity of the blood in one or two animals was determined by the VAN SLYKE and NEILL method. In all dogs recorded post-mortem examination of the duodenum showed that the pancreatic tissue had been completely removed. RESULTS. Normal Dogs (Table I.).-Both the CO2 output and 2 intake increased during the whole period of shivering as compared with the resting period, and in dogs 16 and 17 the volumes of gas respired during the first hour of shivering was about twice that of the resting period. The R.Q. of the first half-hour of the period in which the metabolism of shivering was measured rose to 93 in dog 17, to *83 in dog 17A, and to 79 in dog 19. In a fourth animal, in which for some unaccountable reason the resting 2 consumption was unusually high, shivering did not affect the R.Q. (No. 16 in table). In dogs 17 and 17A the quotients of the second half-hour of shivering were '76 and -86 respectively, whereas in dog 19 it had already fallen to the resting level, which, as a rule, was attained by all animals during the second or third hours of shivering. Diabetic Fasted Dogs (Table II.).-Nine experiments on five depancreatised dogs are recorded in Table II., with results that are essentially the same as those obtained in normal dogs (Table I.). Thus, the 2 consumption during the first half-hour of shivering increased from 45 per cent. (in dog 18 (1)) to 16 per cent. (in dog 1 (3)) above the resting values. In all the experiments except one (dog 9 (2)) the R.Q. of the shivering period rose above the resting level of *68 or *7. The most significant results are the following: In dog 9 (1), which had received no insulin and food for five days, R.Q. was maintained well above -8 throughout the whole period of shivering. In dog 11, which had received no insulin or food for four days, the R.Q. of the first hour of shivering was -83, and during the second hour -76. In dog 18 (1), which had received no food and insulin for three days, the R.Q. of the first half-hour of shivering was -82. As in the normal fasted animals, the R.Q. fell to the resting level during the second or third hour of shivering. That the high quotients observed as a result of shivering cannot be due to a " blowing-off " of CO2 from the blood was shown by a study of

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294 Chaikoff and Macleod the CO2 combining power of the blood of a diabetic dog which was caused to shiver on the third day of fasting by exposing it in a large refrigerator kept at 1 C. Thus, the CO2 capacity of the blood immediately before entering the refrigerator was 65 volumes per cent., and after forty-five minutes' exposure it was 63 volumes per cent. Although it is well known that the excretion of nitrogen does not increase as a result of moderate exercise, it was considered advisable to see whether any change might occur in depancreatised animals under the conditions of these experiments. This was done in dogs 9 (1) and 1 (1) of Table II., with the following results Dog. 9 (1). 1 (3). Grains N exciretecd per hlolii in urine dulriing February 2, March 15, twenty-four hours previouls to shivering. 22-25 Gram.s N excrete(d per h1ourl in urline over February 3, March 16, period in winch anilmal shivered. 22 * O22 t * Aeaswre(l ov-er 5-25 lhours from the beginininlg of shivering. t... ( 5 DISCUSSION. Since protein metabolism is not increased by shivering, as judged by the excretion of nitrogen in the urine, the high respiratory quotients observed in fasted normal and depancreatised dogs during the early periods of shivering is most simply explained by an increased oxidation of carbohydrate. The only other change in metabolism which could possibly account for it is decreased gluco-neogenesis from fat. But, that this cannot explain the rise in R.Q. is evident from the increased oxygen consumption which occurred during the shivering. Indeed, it is much more probable that gluco-neogenesis from fat becomes considerably augmented during shivering. The rise in the quotient indicates, therefore, that the increased oxidation of carbohydrate which sets in immediately shivering starts is not accompanied by a corresponding replacement of this foodstuff by carbohydrate derived from fatty acid. It is only after the glycogen stores originally present in the muscles have become largely expended that fat is called upon to furnish a new supply, and this, no doubt, accounts for the failure of the quotient to remain elevated which is usually observed after the first half-hour or so of shivering. That this falling off in R.Q. is not due to a lessening in the rate of energy production, is indicated by the well-maintained increase in oxygen consumption. When this did decline somewhat, as is shown in some of the observations, it is probable that the body temperature was beginning to fall, though unfortunately this was not measured.

Effect of Shivering on the Respiratory Quotient in Pancreatic Diabetes 295 The results also show that there is no decided difference in the effect of increased muscular activity on the respiratory metabolism of diabetic, as compared with normal, animals, indicating that carbohydrate can be utilised equally well by both. Had the observations been made shortly after feeding, it is possible that the R.Q. would have remained elevated throughout the shivering-at least in the case of the normal animalssince glycogen would then have been available in the liver to replace that used up in the muscles. It would be interesting to repeat these experiments with this point in view. CONCLUSIONS. 1. Shivering in response to cold raises the respiratory quotient and the oxygen consumption of normal and depancreatised dogs to a similar extent. Since no disturbance of the acid-base equilibrium of the organism can be detected, the raised respiratory quotient points to an increase in oxidation of carbohydrate. 2. The increase in R.Q. is marked at the beginning of shivering, but returns later towards the basal level although the increased oxygen consumption is still maintained. This is interpreted as indicating that oxidation of preformed carbohydrate is the only process which is stimulated when the shivering starts, but that a process of gluco-neogenesis sets in later and thus depresses the quotient although as much carbohydrate is still being oxidised. BIBLIOGRAPHY. (1) MACLEOD, J. J. R., Journ. Lab. and Clin. Med. (in press); "The Fuel of Life " (Vanuxem Lectures, Princeton University Press, 1928). (2) HETZEL, K. S., and C. N. H. LONG, Proc. Roy. Soc., 1926, B, xcix. 279. (3) VAN SLYKE, D. D., and J. M. NEILL, Journ. Biol. Chem., 1924, lxi. 523.