Interrelation Between the Change of Blood Pressure and Renin Release

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Renin-angiotensin-aldosterone (RAA) is indispensable as a fundamental factor to regulate blood pressure. In this paper, we want to introduce our studies about the role played by RAA in maintenance and variation of blood pressure. When an anesthetized normal dog which showed an intermediate blood pressure at 120 mmHg underwent bilateral adrenalectomy, his systemic blood pressure lowered to 100 mmHg (one side removed) and 70 mmHg (both sides removed), respectively. At this time, a rapid increase in renin release from both kidneys was considered to constitute the mechanism to prevent shock state. After removing both kidneys, his blood pressure showed an extremely low level (50 mmHg) which has been maintained (Fig.1). In bilateral adrenalectomized dogs, renin release from kidneys increased promptly (within 20 minutes) and maintained the same level after 4 hours. In the dogs with unilateral renal artery constriction, the renin release showed the maximum increase in one hour and maintained the level after 6 hours instead of a significant rise of blood pressure. In the acute stage (1 st-5th week) of Goldblatt's rats, renin content of kidneys on the constricted side showed the maximum increase during the 1 st-2 nd week and was followed by a somewhat decreased level in the 5 th week, in comparison with the 1st-2nd week. The one on the contralateral side decreased gradually from the 1 st to 5th week. Urinary aldosterone showed a variation paralleled with the value of renin contents in bilateral kidneys (Fig. 2). Removing a kidney with constricted artery after the 5th week, blood pressure and urinary aldosterone came back to the nearly normal level immediately. One has no consistent opinion yet about RAA in the chronic stage of Goldblatt's rats. We attempted to perform the experiments in this point. From these experiments, Goldblatt's rats in the 4th-5th and the 18 th month which maintained high blood pressure showed still a high renin level in a constricted kidney and secondary increased urinary aldosterone as an acute stage (Fig. 3). On the other hand, we studied changes in renin release responding to the intrinsic factor in kidneys of dogs. When a clamp was set on abdominal aorta above the junction of renal artery and blood pressure beneath the clamp was maintained at 90 mmHg, the mean blood pressure tended to be raised and both renin release and aldosterone excretion were increased. Addition of mannitol in infusion raised blood pressure a little more than under the former condition, but both renin release and aldosterone excretion were promptly decreased (Fig. 4). On this condition, urinary volume, Na and K in the tubules of kidney acted with high sensibility upon juxtaglomerular cell through macula densa (Fig. 5). Moreover, we examined renin release by means of a new antihypertensive agent, diazoxide, in dogs. This drug has a chemical structure like thiazide diuretics but has sodium retaining effect and a long-acting hypotensive effect even in normotensive subjects. Diazoxide-induced hypotensive dogs, whose renal nerves of one side kidney were resected and contralateral kidneys were removed, showed much less increasing responses of renin release than the dogs with an intact kidney (Fig. 6). In summary, we recognized that RAA was of the most important and fundamental regulating mechanism of blood pressure through several actions such as contraction of arterioles, aldosterone-stimulating effect, sodium balance, catecholamine-stimulating effect and so forth. RAA is very important not only in maintaining normal blood pressure, but also in playing certain roles in various hypertensions and secondary aldosteronism.
Japan Society of Clinical Chemistryの論文

Interrelation Between the Change of Blood Pressure and Renin Release

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