completion of the exercise. Similarly Levine, Gordon and Derick(a3), activity and the excretion of uric acid in the urine forms a very vexed

Transcription

1 THE STATIC EFFORT AND THE EXCRETION OF URIC ACID. BY ROBERT CAMPBELL GARRY. (From the Institute of Physiology, University, Glasgow.) THE relationship, if such there exist, between type and degree of muscle activity and the excretion of uric acid in the urine forms a very vexed question. The problem, like so many others in metabolism, resolves itself more or less into the general question as to what is to be regarded as a significant degree of deviation of the output of any substance from the mean output. This in turn must of necessity depend on the rigidity of the conditions with which the metabolic experiment is conducted, on the attention paid to the technique of analysis and finally on the accuracy of the method employed. In this particular problem there is the further complication as to the exact source of the uric acid excreted. Does it arise only as a waste product of muscle metabolism or may it come from other sources such as, for example, synthesis? Further, the conditions governing the actual excretion of the substance may be of importance. In the first place there seems to be no doubt but that the uric acid content of the blood rises as a result of muscular exercise. Thus Rakestraw(19) found that both a short and a long period of exercise brought about an increase of uric acid in the circulating blood at the time of work. In one experiment a further increase was observed after completion of the exercise. Similarly Levine, Gordon and Derick(a3), examining the blood of athletes within 30 minutes of completion of a Marathon race, found a decided increase in uric acid. The athlete who won the race showed a smaller increase than the others. The authors conclude that the better the training of the athlete the smaller the increase of uric acid in the blood (cf. Dunlop, Noel Paton, Stockman and Maccadam(8)). Burian(2) found an increase in the purine and uric acid content of the fluid used to perfuse the artificially stimulated muscles of a dog, and Macleod(16) found that muscle lost "nucleon" nitrogen as a result of exercise.

2 URIC ACID EXCRETION. 365 There would seem, therefore, to be no doubt in the minds of workers in this field that muscular work does influence purine metabolism, but differences of opinion occur as to whether these disturbances of metabolism are reflected in the urine. Thus Lusk(15) concluded that the character of the urine was unchanged after muscular work. Burian observed on himself an increase of uric acid excretion during the hours immediately following muscle activity, but this was compensated for by a subsequent fall, leaving the total excretion for the 24 hours more or less unaltered. More recently Hartmann(lo), experimenting on the human subject, noticed a fall in the uric acid and P205 excretion during the actual hours of work, followed by a compensatory rise leaving the uric acid content of the 24 hours urine unchanged. This fall during work was attributed to diminished kidney excretion during that period. The inference to be drawn is that the post-work rise was due not to any increased formation or liberation of uric acid but simply to the washing out of the uric acid retained during the work period. The experiments of Rakestraw(19) and of Levine, Gordon and Derick(13) suggest however that this explanation may not be the sole explanation of the subsequent rise. It may be further noted that Hart mann started his purine-free diet only on the night before the day of work and ignored the urine secreted on the day following the exercise. His results therefore are not free from objection. On the other hand Cathcart, Kennaway and Leathes(6) observed an increase in the excretion of uric acid which "follows the exertions and lasts for many hours after them." On examination of their protocols it is seen that this increase appeared on the day of work, usually reaching its maximum on the day following, and it often lasted for at least two days after the actual exercise. A further study of the effect of voluntary muscular activity upon the output of uric acid and the purine bases was carried out by Kennaway(li). Dunlop, Noel Paton, Stockman and Maccadam(s) found that, when the subject was in training, exercise caused a fall in uric acid output; whereas, when the subject was not in training, exercise caused a rise in uric acid excretion. This was not correlated with the observed degree of perspiration which is popularly supposed to be an index of physical fitness. In a recent paper by Cathcart and Burnett(5), where there was no doubt as to the physical fitness of the subject, although the experiments were not directly concerned with uric acid excretion, it is to be 24-2

3 366 R. C. GARRY. noted that, when the subject was on a purine-free diet, there was a small but definite rise in uric acid excretion during the work period. When the diet was changed to one containing purine no rise took place. Hence it follows that the nature of the diet on which the work is performed may play an important role. This raises the question as to the normal endogenous source of excreted purine and the influence which diet may have thereon. Burian and Schur(3) differentiated clearly endogenous from exogenous uric acid and considered hypoxanthine of the muscle to be the chief source of endogenous uric acid. Zwarenstein(22) has recently shown connection between ingested uric acid and creatinine excretion, thus, in his opinion, strengthening the probability of the derivation of uric acid from muscle. Lewis, Dunn and Doisy(14) considered that the increase in uric acid excretion after protein ingestion was due to a general stimulation of all cellular metabolism by the amino-acids. Horbaczewski (cited Burian and Schur(3)) saw in the nuclei of destrqoyed cells, before all in the nuclei of leucocytes, the source of uric acid, going so far as to say that the increase of uric acid in the urine after ingestion of purine-rich food is due to a digestion leucocytosis and subsequent destruction of these cells. It must not be forgotten however that Ackroyd and Hopkins(l) have shown that there is a possibility of synthesis of the purine ring in the body from arginine and histidine. In addition however there is perfectly good evidence that purinefree non-nitrogenous food may quite definitely influence the uric acid excretion. Thus Cathcart(4) showed that on a pure fat diet the uric acid excretion was low in comparison with that on a carbohydrate diet, and he noted that addition of purine-free protein to the diet caused a rise in uric acid excretion. Graham and Poulton(9) confirmed these results while Umeda20), as a result of experimenting on himself and on animals, came to the conclusion that the increased excretion of uric acid on a carbohydrate-rich diet was due to synthesis of uric acid in the body. Macleod and Haskins(rr), on the other hand, considered that the excretion of endogenous purines was not affected by considerable variations in purine-free diet. The possibility of uric acid being " washed out" of the body by large water ingestion is suggested by the work of Cathcart(4). Wilson(21), however, in metabolic experiments where he varied enormously the water ingested, found no constant alteration in uric acid excretion. Another question of some moment is whether the environment can

4 URIC ACID EXCRETION. 367 play any interfering role. Cathcart and Leathes(7) have found that involuntary muscle contraction, in the form of shivering induced by cold, caused a large increase in uric acid output, whereas voluntary muscle exercise, under conditions of warmth, caused a definite fall. The etiology of this marked increase in the case of shivering is complicated by the factor of exposure to cold which can by itself, as pointed out by Cathcart, Kennaway and Leathes(6), cause an increased excretion which " outlasts by many hours the exposure to cold." Since the completion of this work Prof. L eathes has called my attention to, and kindly allowed me to refer to, a communication which he and H. Orr gave to the Physiological Society in June In this work they produced evidence to show that increased muscle tension, brought about voluntarily and apart from any reaction to cold, causes a marked rise in uric acid excretion. In view of these findings it was considered that further investigation into the effects of involuntary muscular activity, with the temperature factor eliminated, might provide information of interest. Present investigation. In the present work the type of muscle activity studied resembled somewhat the involuntary muscle tremor found in the shivering reaction to cold, but any marked temperature alteration was avoided. When muscles are maintained in a state of increased tension a fine fibrillary tremor appears in the muscle substance, but, unfortunately, this strain cannot be maintained for more than an hour or an hour and a half at any one time. In the first few experiments this tremor was induced in the arms alone by pulling against fairly powerful springs, but later, tremor was also induced in the leg muscles by maintaining heavy weights in a raised position by means of a foot lever. This type of activity may be called static work or static effort. The tremor could be felt by the subject of the experiment and also by observers. This tremor must not be considered the same as muscle clonus, in which the muscle as a whole contracts and relaxes rhythmically, for the tremor thus induced by continuing strain did not implicate the muscle belly as a whole but seemed to affect individual bundles of muscle fibres in an inco-ordinate fashion. The tremor became progressively worse, while from time to time a generalised rigor or "shiver " passed over the entire body. Fig. 1 is a trace obtained from the subject's arms during such an experiment.

5 368 R. C. GARRY. Some slight cyanosis was observed in the subject's hands during the experiment. For three or four hours after the experiment the muscles ached dully, there was a tendency to inco-ordination of voluntary movements and the tremor returned on the slightest strain' being thrown on the affected muscles. The following day how- 1 ever there was no pain, no tenderness nor stiffness of the muscles. In one case the course of temperature change was con- LI tinuously followed by means of a rectal thermometer. At the outset, 3 o'clock in the afternoon, the reading was 37.1 C., at the close of one hour's static work it was C.-.E I The diet was purine-free, consisting of 16 oz. white bread, 4 oz. Fig. 1. Tremor. Time in seconds. butter, 3 oz. cheese, 2 pints of (1) At end of 15 minutes. (2) At end of milk (40 oz.) and one apple per 30 minutes. (3) At end of 50 minutes. diem. The calorie content was more than ample, the subject gaining weight slightly. The water ingestion was not rigidly controlled, but its variation was slight, all alterations in urinary output being explainable by variation in environmental temperature, or by perspiration following on the muscular exertion. The daily routine was maintained as uniform as possible. The urine was collected in 24 hour samples from 7 a.m. to 7 a.m. When, as a result of urinary analysis, the subject was judged to be in metabolic equilibrium an experiment was carried out. When the standard level had been restored, without a break in the routine, the experiment was repeated. The methods employed in urinary analysis were as follows: Total nitrogen: Kj eldahl. Uric acid: modification of Hopkins-Folin method. Total purine nitrogen: Camerer-Arnstein. Ammonia: Folin. Creatinine and creatine: Folin. P205: simple titration with uranium acetate solution.

6 URIC ACID EXCRETION. 369 In Table I and in Table II two typical protocols are given in detail. Table I gives an example of the results which were usually obtained and shows clearly the effect of static work on the output of uric acid and on TABLE I. Mean,l A temp. Humi- Urine Uric Other Total NH4 Crea- Crea- Grm. Date F. dity volume acid purines N salt tinine tine P xi xi *28. xi xi Xi xii * Day of static work. "other purines." Table II is given as an example of a slightly anomalous rate of excretion of uric acid. TABLE II. Mean A r temp. Humi- Urine Uric Other Total NH4 Crea- Crea- Grm. Date 0F. dity volume acid purines N salts tinine tine P20& 1. xii xii *3. xii trace xii xii xii Q * Day of static work. In Table II the behaviour of uric acid on the day of static work is worthy of attention. The general rule over the whole series (v. Table III) is a slight increase in uric acid excretion on the day of work, but in certain definite cases, where profuse perspiration had accompanied the muscle strain, and where the volume of urine was in consequence much reduced, a slight fall in uric acid excretion was observed. This is not unexpected from the work of Cathcart(4) v.s. The following day however shows a striking increase in uric acid excretion. Whether this lag in excretion be due wholly to retention in the body as a result of low urinary volume, or due also to delay in formation of uric acid from its precursor, must remain, for the present, a moot point. For the sake of ease of presentation the results of the twelve different experiments are grouped and averaged in Table III. Each experiment is regarded as covering a six day period, two days before the effort, the day of effort and the three following days.

7 370 R. C. GARRY. Average of The days, two days before The days, one day before The days of static work The first days following The second days following The third days following TABLE III. Uric Other Total NH4 Creaacid purines N salts tinine * * * For comparison with these results from the static effort ordinary muscle work was performed under similar conditions of routine and diet. Four such experiments were carried out, walking in the open, walking on a moving platform, performance of work with a bicycle ergometer and with an arm ergometer. Table IV gives one of the protocols and Table V the average of the four experiments. Date 2. ii ii ii ii ii fi. 25 Mean temp * Humidity Urine volume Uric acid Average of The days, two days before the exercise The days, one day before the exercise The days of exereise The first days following the exercise The second days following the exercise The third days following the exercise TABLE IV. Other Total purines N TABLE V. NH4 salts * * Cretinine Creatine Uric Other Total NH4 Creaacid purines N salts tinine ' * * ' Grm. PlO * *99 Grm Grm Discussion of the results. In connection with the static effort there is a definite, although small, rise in uric acid output, an increase persisting for 48 hours after the day of experimentation. This was invariably the case although the results varied in degree. The excretion of other purine nitrogen follows the alteration in the output of uric acid without itself showing much change. Similarly, in ordinary muscle activity, there is an increase in uric

8 URIC ACID EXCRETION. 371 acid excretion but here the increase is somewhat greater. This increase agrees with the findings of Cathcart, Kennaway and Leathes(6). As far as the present results go there is no doubt that muscle activity, be it voluntary or " involuntary" as in the static effort, causes an increase in uric acid excretion. The work of Dunlop, Noel Paton, Stockman and Maccadam(8), of Kennaway(1i), and of Levine, Gordon and Derick(l3) suggests that physical "fitness" may alter the degree of increase in excretion of uric acid in response to muscle activity, this possibly partly explaining the contradictory results to be found in the literature of the subject. In the same way the question of temperature is pertinent. The assessment of the degree of influence which temperature may exert is, however, a very difficult matter. In the laboratory, carrying out routine analysis, the subject is theoretically, although rarely in practice, exposed to a uniform temperature, but once outside the laboratory he is exposed to all the capricious thermal moods of our changeable climate. Cold, especially dry cold, acts as a general metabolic stimulant, and, in this general "tonic" action Cath cart, Kennaway and Leathes see the source of the increased uric acid excretion which results on exposure to cold. At one period of the research there was a short spell of frost and snow. During that period the excretion of uric acid rose far above the usual level. This alteration was coterminous with the period of cold and the rise was well beyond the limit of experimental or day to day variation. As regards the other urinary constituents there is little worthy of note. Nitrogen excretion is increased mainly on the day of work and on the day following, this being less obvious in the static effort group. The alteration in ammonia excretion is not significant. The behaviour of creatinine is peculiar. In the well-known work of Pekelharing(ls), increased muscle tone led to an increased excretion of creatinine, an increase not found after normal muscular exertion. Leathes and Orr(12) confirmed this, though the increased output of creatinine was much less than that of uric acid. In the present series however the static effort shows little effect on creatinine excretion while ordinary muscular work very evidently does so. A trace of creatine was detected but twice as a result of static effort, both times in the urine of the work period; in view of the difficulties of colorimetric estimation, however, all the results in connection with creatinine and creatine are regarded with some little distrust.

9 372 R. C. GARRY. At odd times lactic acid was looked for in the urine of the days of static work. Hopkins' thiophene test was used and was always negative. The excretion of P206 remained constant during muscular work, but on the days of static effort it showed a decided fall. CONCLUSIONS. (1) Static effort of the type employed, as likewise ordinary muscular exertion, increases the excretion of uric acid on the day of work, the increase extending into the two following days. (2) The output of total nitrogen is similarly affected. My most grateful thanks are due to Prof. Cathcart for the suggestion of this work and for his advice and interest during its progress. REFERENCES. 1. Ackroyd and Hopkins. Biochem. J. 10. p :2. Burian. Z. physiol. Chem. 43. p Burian and Schur. Arch. gesamt. Physiol. 80. p Cathcart. This Joumn. 39. p Cathcart and Burnett. Proc. Roy. Soc. B, pp. 99, Cathcart, Kennaway and Leathes. Quart. J. Med. 1. p Cathcart and Leathes. Proc. Roy. Soc. B, 79. p Dunlop, Noel Paton, Stockman and Maccadam. This Journ. 22. p Graham and Poulton. Quart. J. Med. 7. p Hartmann. Arch. gesamt. Physiol p Kennaway. This Journ. 38. p Leathes and Orr. Communication to Physiol. Soc Levine, Gordon and Derick. Journ. Amer. Med. Assoc. 82. p Lewis, Dunn and Doisy. Journ. Biol. Chem. 36. p Lusk. "Science of Nutrition," p Macleod. Z. physiol. Chem. 28. p Macleod and Haskins. Journ. Biol. Chem. 2. p Pekelharing. Z. physiol. Chem. 75. p Rakestraw. Journ. Biol. Chem. 47. p Umeda. Biochem. Journ. 9. p Wilson. Biochem. Journ. 20. p Zwarenstein. Biochem. Journ. 20. p