Effect of Muscular Exercise on Adrenaline and Noradrenaline Secretion of the Adrenal Gland in the Dog

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1 Tohoku J. exp. Med., 1966, 88, Effect of Muscular Exercise on Adrenaline and Noradrenaline Secretion of the Adrenal Gland in the Dog Sennosuke Ohukuzi Deparment of Physiology (Prof. T. Suzuki), Nagasaki University School of Medicine, Nagasaki In 8 unanesthetized dogs, blood samples from the adrenal vein were collected by a modification of the method of Satake and his co-workers, and analyzed fluorimetrically for adrenaline and noradrenaline. Dogs paced by an attendant on a bicycle were run km. Seven out of 8 dogs exhausted completely at the end of running. The adrenaline and noradrenaline secretion rates increas ed markedly in one dog, in which the body temperature rose after exercise above 42.0 Ž. The maximal secretion rate was observed in this case at 15 min after the end of running, and noradrenaline percentage to total catecholamines released from the adrenal gland at this peak time was 40 per cent. In 5 dogs only a slight increase and in the other 2 no increase in adrenal medullary secretion was observed after exercise. Evidence has been presented that muscular exercise elevates urinary excre tion rates and peripheral blood levels of noradrenaline and adrenaline.1-3 Since catecholamines in urine or in peripheral blood were derived from the endings of the adrenergic fibers as well as from the adrenal medulla, a rise in urinary excretion rates or peripheral blood levels of catecholamines does not necessarily mean an increase in adrenal medullary secretion. About 30 years ago, Wada, Seo and Abe4 demonstrated a slight increase in adrenal medullary secretion in dogs after strenuous exercise. In their experiments, blood samples were collected from the adrenal vein of unanesthetized dogs before and after running, and analyzed for adrenaline by the rabbit intestinal segment method. However, no differential estimations for noradrenaline and adrenaline were made in their experiments. In the present study, an attempt was made to evaluate directly the effect of muscular exercise on the noradrenaline and adrenaline secretion by collecting the adrenal venous blood from conscious dogs and analyzing the blood samples differentially. METHODS Eight adult mongrel dogs, ranging in body weight from 11 to 17 kg, were used in the present study. Received for publication, February 3,

2 362 S. Ohukuzi TABLE 1. Effect of muscular exercise on the secretion rate of adrenaline and noradrenaline, the rate of heartbeat and the body temperature in dogs

3 Effeot of Muscular Exercise on Adrenal Medullary Secretion 363 (Continued) * Immeasurably small For collecting adrenal venous blood, a slight modifications of the lumbar route method of Satake, Sugawara and Watanabe6 was applied. The dorsal spinal roots (Th11-L3) were sectioned under sodium pentobarbital (Nembutal 25 mg/kg, i.v.) anesthesia. After this operation the animals were allowed to recover for more than 3 weeks. The adrenal vein cannulation and the collection of adrenal venous blood were performed without anesthesia. The lumboadrenal vein was exposed by the lumbar approach and the accessory side branches of this vein were doubly ligated and cut. A small glass cannula connected with a rubber tube was inserted into the vein just lateral to the adrenal gland. The cannula and the rubber tube were filled with heparin-saline solution in order to prevent blood clotting. A soft silk thread was passed loosely around the adrenal vein between the posterior vena cava and the adrenal gland. After these procedures the animals were allowed to recover for about 18 hours. An adrenal venous blood sample for measuring the basal secretion rate was collected. Then the animals, paced by an attendant on a bicycle, were run km at average speeds of m per min. Adrenal venous blood samples were collected again at 3, 15, 30 and 60 min after the end of muscular exercise. At the time of adrenal venous blood collection the soft silk thread around the adrenal vein was gently pulled and the clamp on the rubber tube was removed. The amount of adrenal venous blood collected at each period before and after exercise was ml and duration of blood sample collection was sec. The blood samples were immediately centrifuged. One ml of the adrenal venous plasma was mixed with 1 ml of 2% sodium fluoride plus 3% sodium thiosulphate solution.? Then, 10 ml of acetate buffer solution were added. An adsorption, elution and estimation of adrenaline and noradrenaline were carried out by the method of Euler and Lishajko.8 RESULTS All of the dogs except one (dog 7) exhausted completely at the end of running with vigorous panting and salivation. They lay down stretching their legs. One of them (dog 8), however, recovered from exhaustion within a few minutes and became active. Dog 7, which was run for a relatively long dis-

4 364 S. Ohukuzi tance, did not exhaust completely, though panting and salivation were observed at the end of running. The adrenal medullary secretion rates, the rates of heartbeat and the body temperature are listed in Table 1. A slight increase in adrenal medullary secretion was observed in 5 dogs (dogs 1-5) and a marked increase in one dog (dog 6). In the other 2 (dogs 7 and 8) no increase in adrenal medullary secretion occurred after exercise. In dog 6 the secretion rate was ƒêg/kg/min for adrenaline and 0.003,ƒÊg/ kg/min for noradrenaline before running. At 3 min after the end of running it increased to ƒêg/kg/min and 0.041,ƒÊg/kg/min, respectively. The maximal secretion rate of adrenaline and noradrenaline, which was observed at 15 min after the end of running, was 0.25ƒÊg/kg/min and 0.17 ƒêg/kg/min, respectively. Noradrenaline percentage to total catecholamines was 40 per cent. In this case the body temperature rose from 39.1 Ž to the level above 42.0 Ž. The heartbeat became too fast to be counted exactly. In dogs 1-5 the adrenal medullary secretion rate increased only slightly. The maximal secretion rate of adrenaline plus noradrenaline was not more than 0.060,ƒÊg/kg/min. It was observed at 15, 30 or 60 min, but not at 3 min after the end of running. In these cases the body temperature rose definitely after run ning and attained Ž, while it was measured before running as C. The rate of heartbeat increased without exception. In dogs 7 and 8, though there were rises in body temperature and rate of heartbeat, no increases in adrenal medullary secretion were observed. DISCUSSION In the present study only a slight increase in adrenal medullary secretion was observed after exhausting exercise in most cases. This agrees well with the report of Wada, Seo and Abe.4 As to the effect of muscular exercise on adrenal cortical secretion in dogs, a marked increase in 17-hydroxycorticosteroid (17-OHCS) secretion was always observed in experiments of Suzuki et al.0,10 after exhausting exercise. Thus, it seems justifiable to conclude that the adrenal medullary response is less sensitive than the adrenal cortical response to muscular exercise. Similar results have already been obtained in cyanide-experiments of Suzuki and his co-workers." They evaluated the adrenal medullary and 17-OHCS secretion in response to cyanide anoxia by collecting the adrenal venous blood and analyzing it for catecholamines and 17-OHCS. After subcutaneous injection of potassium cyanide in doses of 1-3 mg/kg the secretion rate of 17-OHCS increased definitely, while that of adrenal medullary hormones showed no increase. On injecting 4 mg/kg potassium cyanide, increases both in 17-OHCS secretion and adrenal medullary secretion occurred.

5 Effect of Muscular Exercise on Adrenal Medullary Secretion 365 It is of interest that in experiments of the present study there was a delay in reaching maximal secretion rate of adrenal medullary hormones after exercise. The maximal secretion rate was observed at 15, 30 or 60 min, but not at 3 min after the end of running. However, the underlying mechanism of this delay is not clear. In one dog (dog 6), in which the secretion of adrenal medullary hormones in creased markedly after running, a rise in body temperature up to the level above 42.0 Ž was observed. Since the experimental results of Saito12 showed that a marked elevation of body temperature (up to 41.3 Ž) produced a definite increase in adrenal medullary secretion in conscious dogs, an acceleration of the secretion rate observed in dog 6 of the present study might be connected with the effect of hyperthermia. Some investigators reported an increase in urinary excretion of catecholamines, mainly noradrenaline, following exercise.1,3 In the present study, however, no predominant secretion of noradrenaline from the adrenal gland was observed after exercise. This discrepancy might be explicable by the fact that urinary noradrenaline was derived from the endings of adrenergic nerve fibers as well as from the adrenal medulla. Acknowledgment The author wishes to thank Dr. H. Matsui for his kind co-operation. The author is also very grateful to Professor T. Suzuki for his help in revising the manuscript. References 1) Euler, U.S.v. & Hellner, S. Noradrenaline excretion in muscular work. Acta physiol. scand., 1952, 26, ) Gray, I. & Beetham, W.P., Jr. Changes in plasma concentration of epinephrine and norepinephrine with muscular work. Proc. Soc. exp. Biol. Med., (N.Y.), 1957, 96, ) Ishihara, I., Saka, Y. & Ishigaki, K. Neuroendocrine regulatory system in fatigue. 1. Urinary excretion of catecholamines and 17-hydroxycorticoids after muscular exercise. (Jap.) Ann. Rep. Res. Inst. Environ. Med. Nagoya Univ., 1958, 10, ) Wada, M., Seo, M. & Abe, K. Effect of muscular exercise upon the epinephrine secretion from the suprarenal gland. Tohoku J. exp. Med., 1935, 27, ) Suzuki, T., Yamashita, K. & Mitamura, T. Effect of ether anesthesia on 17 hydroxycorticosteroid secretion in dogs. Amer. J. Physiol., 1959, ) Satake, Y., Sugawara, T. & Watanabe, M. A method for collecting the blood from the suprarenal gland in the dog, without fastening, narcotizing, laparotomy or provoking any pain. Tohoku J. exp. Med., 1927, 8, ) Weil-Malherbe, H. & Bone, A.D. The chemical estimation of adrenaline-like substances in blood. Biochem. J., 1952, 51, ) Euler, U.S.v. & Lishajko, F. The estimation of catecholamines in urine. Acta physiol. scand., 1959, 45, ) Suzuki, T., Yamashita, K. & Mitamura, T. Muscular exercise and adrenal 17

6 366 S. Ohukuzi hydroxycorticosteroid secretion in dogs. Nature (Lond.), 1958, 181, ) Suzuki, T. Effect of non-exhausting and exhausting exercise on adrenal 17 hydroxycorticoid secretion rate in the dog. Abstracts of papers XXIII Internat. Congr. Physiol. Sci., 1965, ) Suzuki, T., Yamashita, K., Hirai, K., Kurouji, K-I. & Yoshio, H. Adrenal 17 hydroxycorticosteroid secretion in response to cyanide anoxia. Pfliigers Arch. ges. Physiol., 1965, 285, ) Saito, S. Influence of application of cold or heat to the dog's body upon the epinephrine output rate. Tohoku J. exp. Med., 1928, 11,