STUDIES OF RENAL FUNCTION BASED ON WATER METABOLISM

Abstract

In this paper an attempt was made to modify the common concentration test of renal function with posterior pituitary extract. Further the studies were intended to judge the segmental function of the water dependent nephrons by using the creatinin and the osmoral clearances at the same time during the above test. In the test, the input and the output of body fluids were adjusted every 30 minutes to maintain the level of body fluids. Two hours after the initial intake of 600ml water, 100mu of atonin, the posterior pituitary extract was subcutaneously administered. In 26 healthy adults the difference of the values of specific gravity before and after the administration of atonin was 15.0±3.9.
In these experiments the osmotic pressure and the volume of the urine were investigated. It was found that the mechanism of the “Atonin test” was quite similar to that of the concentration test and that the specific gravity method served better than the urine volume method as an index of osmotic pressure which represents the concentration of urine directly. Although from the stand point of technical errors in the measurement, the osmotic pressure and the urine volume methods were more accurate than the specific gravity method.
In the same experiment the creatinin clearance, the difference of creatinin u/p ratios before and after the administration of atonin, the dffference of osmoral u/p ratios before and after the administration of atonin and the creatinin/osmoral clearance ratio were investigated. In healthy adults the mean value of each of these 4 investigation subjects was 98.0±13.7ml/min., 61.6±25.5 1.55±0.40 and 42.0±10.2 respectively.
Since the creatinin clearance represents GFR, the difference of creatinin u/p ratios the reabsorptive function of the total renal tubuli, the difference of osmoral u/p ratios the selective reabsorptive ability of the distal tubuli and the creatinin/osmoral clearance ratio principally the obligative reabsorptive ability of the proximal tubuli, —though in the last ratio the osmoral diuresis caused by exogenous osmotic substances, urea or salt should be excluded—the renogram which is shown by the creatinin clearance and the indices of water reabsorptive ability is also helpful in judging the segmental function of the nephrons. The fact that indices of water reabsorptive ability does not require the measurement of urine volume and much specimen is of great advantage to study the differential renal function.