No abstract

Estimates of glomerular filtration rate, effective renal plasma flow and tubular excretory capacity of the kidney by the methods introduced by Smith and his co-workers (1, 2) show variations not only between tests made on the same individual on different days but also between consecutive urine collection periods within the same test. Although it is known that the methods are adequate for demonstrating individual differences in renal function, no quantitative estimates of the accuracy of the experimental technique or the day-to-day fluctuations in renal function in the same subject have been made. Acute experiments as well as studies of the effects of an experimental regime over a period of days or weeks require for their interpretation knowledge of the magnitude of both sources of variation in kidney function.The purpose of this study was to define the limits and to determine how much of the total variation between tests can be attributed to day-to-day physiological changes in the individual and how much can be attributed to short term changes. While part of this short term variation may result from physiological changes in the subject, it may be regarded as experimental error since it is inherent and unavoidable in the method itself. METHODSExperimental technique. Determinations of inulin clearance, diodrast clearance and diodrast Tm were carried out according to the technique previously described (3,4). Minor modifications in the experimental procedure reported included the following: use of 1: 500 nupercaine in saline in the bladder at the beginning of catheterization and again before removal of the catheter; the use of procaine hydrochloride for arterial and venous punctures; the use of the femoral artery for obtaining blood samples in the majority of tests; and maintenance of subjects in a post-absorptive state for the duration of the experiment. In addition, collection periods were shortened 1 Present address: Department of Internal Medicine, Washington University School of Medicine, Saint Louis, Mo.to eight to 11 minutes instead of the previous 12-to 14-minute periods. Four urine collection periods were taken for the estimation of clearance values followed by four periods of the estimation of Tm on each test.Subjects. Male subjects were selected according to criteria previously described (3,4) Table I by the analysis of variance (5). In certain in-TABLE

No abstract

No abstract

No abstract