By comparison of the I' P chloride ratio in terms of the L-P inulin. we have attempted to obtain information concerning the behavior of the renal tubules toward chloride of patients with "essential hypertension."Methods. The experimental series consists of 38 periods determined upon 10 patients with essential arterial hypertension: in the control group 12 normal individuals furnished a total of 34 periods. The tests were performed in the n~orning, in the fasting state. The usual technic for the inulin clearance was employed, 3 periods of 15 to 30 min being taken. Vrine specimens were collected by catheterization and rinsing of the bladder with sterile water. The blood for the chloride determinations was taken under oil, and estimations were done on serum and quoted in terms of sodium chloride. Analysis for chloride concentration was done by the method of Sendroy.' Determinations of inulin were carried out by the method of Corcoran and Page.?Results. The renal tubules in hypertension were found to reabsorb significantly less chloride in relation to the C/P inulin than did those of normal subjects.Discussion. The patients included in the experimental series were for the most part in the younger age groups, and bore the clinical designation of "essential hypertension." Those in whom the inulin and diodrast clearance suggested a definite renal involvement were also excluded. In this way it was hoped that the results would not be confused by ancient or generalized infectious or degenerative processes and would therefore represent as specifically as possible the functional patterns of uncomplicated hypertension.The normal subjects were drawn chiefly from the gynecological service and included younger women who were suffering from relatively minor complaints without renal or vascular implications. The tests were performed either prior to surgery or several weeks post-operatively, at such time as recovery was complete and the patients were ambulatory. All subjects were on the general diet, and all were similarly hydrated in preparation for the test. Differences in previous chloride intake were therefore dependent only upon personal variation and were presumably inconspicuous. In general, then, it seems justified to assume conditions of chloride equilibrium.Whether the observed differences are to be interpreted as indicating specific changes in the tubular cells with respect to permeability toward chloride, increased velocity of tubular urine flow, or even a hormonal influence, the present data do not enable us to determine. Further studies are therefore under way which may further clarify the problem.Summury. The clearance of chloride was studied simultaneously with that of inulin in hypertensive and in normal individuals under standard conditions of mineral intake and hydration.The cases investigated showed no evidence of urinary tract or other pathology to which an etiological relationship might be attributed. The hypertensive subject is demonstrated to reabsorb chloride to a substantially lesser extent than does the n...
The threshold theory of chloride excretion was formulated by Rehberg (1) in 1926. Chloride studies in recent years have included those of Dillon (2), Hare, Hare and Phillips (3), Shannon (4) and Wolf (5). Pitts in 1945 (6) considered chloride with reference to renal methods for the acidification of urine, and Wolf applied the law of exponential decay to his analysis of chloride disposal under varying infusion loads and at varying time intervals. He found certain "critical concentrations of infusion fluid and urine, at which neither solute nor water are retained from an infusion, relative to one another." This study is' thus an extension of Rehberg's threshold studies, through the extremes of load, and confirms the impression of a "plasma concentration above which chloride is excreted relative to water, and below which chloride is retained relative to water." Wolf also finds a "distortion or departure from normal of the ratio of chloride to non-chloride space, induced by this load."Our interest in chloride metabolism was stimulated by an observation made in the course of routine clearance studies done upon a group of patients suffering from essential arterial hypertension (7,8). It was found that the clearance of chloride in such patients tended to parallel the urine output, whereas in normal subjects the chloride clearance remained within a certain range, regardless of the volume output. In a preliminary series, values of chloride clearance periods rose as high as 6.6 ml. per minute, with a urine output of 7.4 ml. per minute, while control subjects tended not to exceed values of 3.0 to 3.4 ml. per minute, even with a urinary flow of 11 to 12 ml. per minute. We then attempted to investigate the mechanism of this phenomenon and hence to arrive at an evaluation of its significance and implications. The technique of multiple clearance was chosen because it supplied us with the filtration rate, the effective renal blood flow, and, by calculation of the U/P inulin, a helpful index to water reabsorption. It will be readily seen that the ratio of urine concentration to plasma concentration, or U/P inulin, is serviceable in 2 important respects, namely, that the complete filtration of inulin through the glomerular membrane is thoroughly established, and the concentration in the filtrate is known to equal that in the plasma; and secondly, that it is inert in the tubules. The U/P inulin can, therefore, be altered only by a change in the volume of the solvent. Such a change would, in the light of present concepts of renal physiology, be accomplished by reabsorption of water by the tubules. Thus, a U/P inulin of 100 indicates that the urine is 100 times as concentrated as the plasma, and that the corresponding volume of water has been reabsorbed from the glomerular filtrate. Likewise, if the U/P inulin is 1, then no water has been reabsorbed; the urine concentration equals the plasma concentration, and the urine flow is equal to the filtration rate.Adopting, then, the inulin ratios as a measure of tubular reabsorption of wat...
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