Eaton M. MacKay

THE RELATION BETWEEN THE BLOOD UREA CONCENTRATION AND THE AMOUNT OF FUNCTIONING RENAL TISSUE

The concentration of urea in the blood is dependent upon the rate of urea formation and the rate of urea excretion. Urea formation varies with the protein content of the diet and with the rate of protein metabolism while the rate of urea excretion is influenced by many factors (1). As a result the blood urea concentration normally fluctuates through a considerable range of variation. However, unless under exceptional circumstances, the upper limit attained is comparatively low so long as there is no reduction in the amount of functioning renal tissue. The marked increases in the concentration of urea in the blood which are seen in the terminal stages of Brights disease when the amount of functioning renal tissue is presumably greatly reduced occur too often to require comment but concerning the degree to which the amount of renal tissue must be reduced before an increase in the blood urea concentration over the normal limits ensues nothing definite is known. It is even questionable whether the transient increase in the blood urea concentration which follows the removal by operation of half of the renal tissue of the body (2) can be ascribed to the reduction in kidney substance. Such an increase might well be a result of an acceleration of protein catabolism and might occur after any sufficiently severe operative procedure. In an attempt to throw some light on these questions a study has been made in a group of patients of the relation between the degree of geduction in the amount of functioning renal tissue and the degree of increase in blood urea concentration.

Deleterious Effects of Insulin Shock

The effects of a hypoglycemia of long duration on the various tissues and the organism as a whole are of fundamental importance. On the practical side the possibility of the use of excessive doses of the new slow acting protamine insulin by untrained individuals, because of the lack of immediate results or the accidental administration of the concentrated precipitate from a vial which has not been agitated, make essential a knowledge of the effects of hypoglycemia due to insulin shock. In experiments on dogs we have found that when a state of insulin shock is maintained for 24 hours or longer with protamine zinc insulin it is apparently impossible to resuscitate the animal and death always ensues. Often this result follows when the period is shorter. A typical protocol follows: A male dog weighing 29 kg., last fed the day before the experiment started, was given 40 units (1 cc.) of protamine zinc insulin,∗ and 23 hours later 20 units more. Five hundred cc. of fluid were given by stomach tube at 23, 30, 38, 50, 57, and 71 hours. With the exception of the first dose this was 10% sucrose and at 38 and 57 hours 5 gm. of sodium chloride were also administered. The blood sugar concentration was 61 mg. % at 0 hours and 22 at 6.5, 36 at 23, 28 at 25, 22 at 30, 28 at 38, 73 at 47, 52 at 50, 67 at 56, 41 at 71, and 67 mg. % at 73 hours respectively. At this time the dog died, apparently of circulatory failure. The animal had his first convulsion 7 hours after the first dose of insulin and became unconscious within 13 hours. He never came out of this coma which after 40 hours could have had no relation to the blood sugar concentration at the moment. In other experiments milk or milk and sugar has been given with the same result. In many of our experiments death has resulted from hypoglycemia before sufficient sugar was administered. So far we have had seven animals in which death ensued long after the blood sugar level had been returned to normal. Fat and well nourished dogs appear to suffer less from the hypoglycemia than thin ones. Experiments are being carried out in an attempt to determine the relation of the undesirable effects of insulin shock to the hypoglycemia itself and to the secondary effects on the circulation and other body mechanisms. An important point is the length of the shocking period which is necessary to produce such damage-that recovery does not occur. Grossly the brains do not appear particularly abnormal, but it seems possible that damage to the brain, analogous to that due to anoxemia, may explain the untoward effects of hypoglycemia. Insulin shock is being purposely used in schizophrenia therapy 1 , 2 and Steinfeld 3 has reported that circulatory collapse or epileptiform convulsions are serious side reactions which may occur even when the blood sugar has again been raised to a normal level. We have seen this happen in our experiments and hypoglycemia is obviously not the immediate cause of the death of our animals.

STUDIES OF SODIUM AND POTASSIUM METABOLISM. THE EFFECT OF POTASSIUM ON THE SODIUM AND WATER BALANCES IN NORMAL SUBJECTS AND PATIENTS WITH BRIGHT'S DISEASE

The work presented here was undertaken primarily for the purpose of ascertaining the effect of the ingestion of moderate amounts of potassium on the sodium balance of normal individuals and patients with Brights disease. It was felt that such information would be of particular significance in appraising the efficiency of potassium salts as diuretics in the treatment of nephritic edema. Potassium chloride was selected as the means of administering the potassium in order to avoid the alkaline or cathartic effects of other potassium salts. Incidentally, the experiments in supplying complete data on sodium and potassium balances and weight changes provide an opportunity for correlating sodium and potassium balances with the water balance of the body.

Hyperalimentation in Normal Animals Produced by Protamine Insulin

Beginning some years ago there were clinical reports 1 2 3 4 5 that undernourished, non-diabetic patients gained weight under the influence of insulin. The latter is regarded as stimulating the appetite, leading to a higher caloric intake of food. It is now used for this purpose by many although good proof that it is efficacious is still lacking. The reason for this is because of the many factors involved in such clinical observations. Experiments on animals have been‘ disappointing, such as the negative results recorded for rabbits. 6 In experiments on normal rats carried out some seven years ago with ordinary insulin we were unable to influence either the food intake or body weight. In an attempt to duplicate experimentally with protamine insulin the occurrence of fatty livers, which has been attributed to chronic hypoglycemia in patients, 7 we were surprised by the marked influence on alimentation. A typical experiment is presented in Fig. 1. Each group of rats was composed of 3 adult males of about the same weight. They were on a diet supplied ad lib. and containing casein 25, starch 40, butter fat 15, lard 10, brewers yeast 5 and standard salt mixture 5. Protamine zinc insulin∗ was given subcutaneously in doses of 8 units (0.2 cc.) per rat, twice a day as a rule. The increase in food intake is remarkable and there is a corresponding increase in body weight. When insulin injections are stopped the compensatory decrease in food intake is interesting. A food box was accidentally left out of the cage of one insulin-treated group for only 4 hours and all of the rats died in hypoglycemia before it was returned. Other details will be brought out in a later report.

THE ANTIKETOGENIC ACTIVITY OF SUCCINIC ACID.

Koranyi and Szent-Gyorgyi have reported (1, 2) that relatively small doses of succinic acid would reduce or abolish the ketosis in diabetes. Wehave been unable to demonstrate this action of succinic acid. In Table I are presented three typical examples of the result of administering succinic acid to diabetic patients. All of these patients had been on their regime for some time and their diets were constant. They were given the free acid. The total ketone bodies in the

Effect of Histamine Pretreatment upon Adrenalectomized Rats

There are many features of histamine “shock” and the “intoxication” of adrenal insufficiency which are similar. Karady has found 1 that the incidence and severity of surgical shock or histamine shock in the rat may be reduced by previous treatment with histamine. We have found that pretreatment with increasing doses of histamine will increase the resistance of adrenalectomized rats to certain procedures to which they are ordinarily very susceptible. Bilateral nephrectomy causes a marked decrease in the survival time of rats from which both adrenals have been removed. 1 , 3 Sixteen male albino rats weighing from 144-193 g were divided into 2 groups with an average weight of 170 g. The histamine-treated group was given a 10% suspension of finely ground crystals of histamine dihydrochloride in olive oil so that its action might be more protracted. 4 Ten nig were administered subcutaneously daily for 6 days, followed by 20 mg per day for 8 days more, a total of 220 mg per rat. At this time the 2 groups still weighed about the same but the histamine-treated rats appeared to be in the poorer condition. Sixty hours after discontinuing the histamine treatment the adrenals and the kidneys were removed from all of the rats. In the histamine-treated group the cortex of the adrenal gland had become hypertrophied so that the adrenals of this group weighed 31% more than those of the controls. The survival time of the 2 groups of rats was quite at variance with their appearance. The untreated controls survived for from 25 to 41 hours with an average of 34.6 hours. The histamine-treated group, on the other hand, lived from 43 to 73.5 hours with an average of 56.8 hours, an increase in the average survival time of 64%.

Virucidal (Rabies and Poliomyelitis) Activity of Aqueous Urea Solutions

In an attempt to bring the suspended particles of an aqueous spinal cord suspension containing rabies or poliomyelitis virus into more intimate contact with inactivating agents for vaccine production trials a “solution” of the cord was made with the aid of urea. The effect of urea in strong concentration on these viruses proved interesting. As first recorded by Spiro 1 and in more detail by Ramsden 2 urea in aqueous solution has a remarkable ability to “dissolve” proteins. When spinal cord of the rabbit or monkey, moist with saline, is placed in a mortar and urea crystals added the cord on trituration quickly passes into an opaque syrupy “solution” containing innumerable lipid droplets in suspension. In this manner a 50% cord “solution” containing from 30% to saturation with urea is easily obtained. Rabies Virus. Typical results are presented in Table I. The fixed rabies virus usually killed within 6–11 days after intracerebral inoculation. The non-urea treated virus suspension was a 20% concentration of cord and brain in saline. The urea treated preparation contained 50% of cord-brain and about 40% of urea. Rabbits 3 and 4 were injected intracerebrally within an hour after the preparation of the cord “solution”. They were given a second injection of 0.2 cc. each of a urea-treated preparation 10 days after the first ones with no ill effects. Rabbits 5 and 6 were given injections of 0.1 cc. each of the non-urea-treated preparation 3 weeks after the first injections. Both of them died within a week. Rabbit No. 7 was given a weekly “vaccination” by a 1.0 cc. subcutaneous injection of the 50% urea-treated rabies cord preparation for 6 weeks and then inoculated intracerebrally

Effect of Acid Extract of Anterior Pituitary on Iodine Content of Blood and Thyroid in Guinea Pigs.20

Loeb, Bassett and Friedman, Siebert and Smith, and Martin Silberberg 1 , 2 , 3 , 4 , 5 have shown that injections of acid extract of cattle anterior pituitary produce changes in the guinea pig which bear close resemblance to the changes found in man in cases of Graves disease, as far as the structure of the thyroid gland, the behavior of the colloid, the changes in weight, as well as in the basal metabolism and the effect of KI in this condition are concerned. Lunde, Closs and Wülfert 6 have shown that the acetone insoluble or globulin-iodine fraction of the thyroid gland of toxic goiters is both absolutely and relatively decreased, while the total blood iodine concentration has been found by Lunde, Closs, Pedersen, 7 , 8 and others 9 , 10 to be increased. There is reason for assuming that an increased elimination of the thyroid hormone from the gland into the circulation takes place in Graves disease. We wished to determine whether similar changes in the iodine distribution occur in the guinea pig under the influence of acid extracts of cattle anterior pituitary. We carried out 2 experiments. In the first, 8 guinea pigs, ranging in weight between 170 and 210 gm., were injected 5 times over a period of 6 days with 1 cc. of the acid extract. The pooled thyroid glands and 8 blood specimens of these animals were analyzed for their content in alcohol soluble and insoluble iodine. The thyroids and blood from 12 control guinea pigs of a similar weight were analyzed in the same way. In a second experiment, corresponding analyses of the blood and the thyroid glands from 12 injected and 12 control guinea pigs were carried out. In this case 6 samples of blood were analyzed separately from controls and 6 samples from the injected animals.

Phosphate and Kidney Weight

The addition of a certain amount of sodium phosphate to the food of young albino rats is followed by a remarkable increase in the weight of the kidneys, an increase which considerably exceeds that which is found after the ingestion of excessive amounts of other minerals or of protein. Female rats, 30 days of age at the beginning of the experiment, were given a casein-starch-lard diet in which adequate concentrations of cod liver oil, yeast, wheat germ and salt mixture were incorporated. To other groups of animals the same diet was given, except that part of the corn starch was replaced by acid or alkaline sodium phosphate. The total phosphate (PO4 concentration in the control diet was 0.68 per cent, in the acid phosphate diet 5.03 per cent, and in the alkaline phosphate diet 5.02 per cent. Measurements of food consumption showed that nearly equal amounts of food were taken by each group. After 44 days the rats were killed. The kidney weights are given in Table 1. No such pronounced increases in kidney weight were seen in similar experiments in which as much or more sodium than was taken in the above experiments was given in the form of sodium chloride or sodium bicarbonate. Parallel experiments showed that neither acid nor alkaline phosphate had any effect on the degree of compensatory hypertrophy of the kidney after unilateral nephrectomy.

Compensatory hypertrophy of the kidney: The effect of pregnancy and of lactation

The stimulus to compensatory hypertrophy was given by the removal of one kidney from a rat. The degree of hypertrophy was measured by comparing the weight of the remaining kidney forty days after the operation with the weight of the kidney of rats in which one kidney had been exposed but not removed. This value is expressed as a percentage. Thus if the weight of one kidney of the control rat was 1000 mg. and the weight of the remaining kidney in the nephrectomised rat was 1300 mg., the degree of compensatory hypertrophy was 30 per cent. The percentages given are the averages of groups of rats. It was intended that there should be 25 rats in each group, but since all of the animals did not become pregnant at the expected time this number was not reached in all of the experiments. The diet used was adequate for growth and for reproduction and contained 17.8 per cent of protein, 24.9 per cent of fat, and 42.2 per cent of carbohydrate. The amount of food taken was nearly the same in all experiments except in the lactation experiment. In this instance the caloric intake rose from 25 calories to 90 calories per 100 grams of body weight per day.