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KMID : 0377619610010030343
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Korean Jungang Medical Journal
1961 Volume.1 No. 3 p.343 ~ p.365
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ANALYSIS OF VARIOUS RENAL FUNCTIONS IN THE KOREAN
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Abstract
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Physiology of the kidney has shown a remarkable progress in past and thus many renal function tests have been designed by various investigators. However, some of these tests are developed rather recently by preclinical investigators and are still impractical from the clinical point of view. As-a result, these function tests are not widely applied to the clinical practice and, hence, certain important renal functions are not well established to the date.
Moreover, some renal functions are known to be modified by many factors. For instance, the amount of daily protein intake is known to regulate the renal concentrating ability, which can be reversed upon returning to. the usual high protein diet. This observation has a paramount importance to us when one considers the fact that the majority of Korean people are living on a low protein diet.
In spite of these facts, very little is known about various renal functions of the normal Korean, with the result that it is virtually impossible to critically evaluate the renal functions of patients in the clinical practice. Therefore, this investigation was undertaken to analyze renal function of the Korean as thoroughly as possible by means of all the known , tests regardless of the clinical
applicability. In the final analysis, results were compared with those obtained in other countries and attempts have been made to explain the differences between the Korean and others. The following renal functions were studied in this investigation:
(A) Renal Hemodynamics
(a) Glomerular filtration ´rate (b) Renal plasma flow
(c) Filtration fraction
(d) Renal blood - flow ` (B) Diluting Capacity
(C) Concentrating Capacity
(a) ADH-induced
(b) Dehydration-induced
(c) Maximum free-water extraction during mannitol diuresis(TcmH_20)
(D) Tubular Reabsorptive Capacity of Glucose (TmG)
(E) Tubular Secretory Capacity of PAH (TmPAH)
(F) Tubular Reabsorption of Urea
In total, 46 healthy Koreans (42 males and 4 females) whose age ranged from 18 to 37 years old were used in this investigation.
In most tests, both insulin and PAH clearances were routinely determined as measures of the glomerular filtration rate (GFR) and the renal plasma flow (RPF), respectively. All the numerical figures indicating various renal functions ´were recalculated for the body surface area of 1.73m2 and the values of standard deviation were also calculated in order that these values can be compared with those reported in other countries.
Results obtained from various function tests may be briefly summarized as follows
(A) Renal Hemodynamics
(a) Glomerular filtration rate: In 37 subjects, the insulin clearance was, measured in order to determine the glomerular filtration rate. A priming dose of 50 mg of insulin per kg was injected intravenously, followed by a sustaining dose of 32.5 mg per min. The average insulin clearance was 117±21.9 cc/min.
(b) Renal plasma flow: In 25 subjects, the PAH clearance was measured for the determination of renal plasma flow. As a priming dose, 8 mg of PAH per kg was injected intravenously, followed by a sustaining dose of 12 mg per min during the experimental period. The average PAH clearance was 706±149.5 cc/min.
(c) Filtration fraction : As calculated from the above results, the filtration fraction was averaged to be 0.17±0.037.
(d) Renal blood flow. The hematocrit ratio was determined in 8 subjects along with the PAH clearance, in order to calculate the renal blood flow (RBF). The calculated renal blood flow was 1133±85 cc/min.
(B) Diluting Capacity :In 6 subjects, 1000 cc of water was initially given following which the amount of water excreted in urine was replaced during the experimental period. During maximum water diuresis, the urine osmolarity and the urinary concentration of chloride were averaged to 105±12_ .5 mOsm,/L and 26?7.0 mEq / L, respectively whereas the maximal urine flow and the osmolar clearance were averaged to be 20.0±3.7 and 6.8± 1.6cc / min , respectively, with the result that the positive free-water clearance (CHEO) was calculated to be 13.2± 2.2 cc/ min.
(C) Concentrating Capacity
(a) ADII-induced: In 4 hydrated subjects, a priming dose of 200 mu of pitressin was given intravenously following which a sustaining dose of 4 mu per min was infused throughout the entire experimental period. At the peak of maximum antidiuresis,the urine osmolarity and urinary concentration of chloride were averaged to 630±146mOsm / L and 210±64 mEq / L , respectively; the average negative free-water clearance (TcH2O) was 3.2±0.6 cc/min..
(b) Dehydration-induced : In 8 subjects(4 males and 4 females),the water intake was completely prohibited for at last 12 hours prior to the experiment during which samples of the maximally concentrated urine as well as plasma samples were obtained. The plasma osmolarity and the chloride concentration of plasma were averaged to be 304±24.3mOsm / L and 112±7.6mEq / L, respectively, whereas the urine osmolarity and the chloride concentration of urine were averaged to bs 1172±266mOsm / L and 312±84.8mEq / L,´ respectively. The averageurine flow and the osmolar clearance were 0.35±0.05cc/min and 1.2±0.67cc/min, respectively, with the result that the negative free-water clearanceTcmH2O was 0.89/ 0.47cc±min. The U/ P osmolar ratio was, on the average, 3.84±0.83.
(c) Maximum free-water extraction during mannitol diuresis(T´mH2O): In 5 subjects, a priming dose of 200 mu of pitressin was given intravenously following which 4 mu of pitressin per minute was constantly infused during the entire experimental period, while 20% mannitol solution was infused as rapidly as possible. During the maximum urine flow, the urine osmolarity was 448±54mOsm/L and calculated Tcmg2Owas 4.2±1.3cc/min.
(D) Tubular Reabsorptive Capacity of Glucose(TmG) : In 5 subjects, a priming dose of 125 gm of dextrose in 50% solution was given intravenously, followed by a sustaining dose of 2 gm / min, in order to raise the plasma level of glucose. The average plasma level of glucose was 623±160mg°o while the calculated TmG was 280±41.1mg/min.
(E) Tubular Secretory Capacity of PAH(TmPAH) : In 5 subjects, a priming dose of 160 mg of PAH per kg was given intravenously, followed by a sustaining dose of 120 mg/min. The plasma concentration of PAH was maintained, on the average, at the level of 30.2±12.3 mg v. and the ´ calculated TmPAH was 93±25.8mg/min, ,
(F) Tubular Reabsorption of Urea : In ´-6 subjects, the average urea clearance
was 51.6±9.5 cc/min which was equivalent to 0.399±0.061 of the insulin clearance.
When the above described results obtained from the normal Korean are compared with those reported in other countries, the following conclusions may be drawn (A) Although the value of GFR was somewhat lower while RPF was somewhat higher in the Korean as compared to the corresponding values reported in the U.S.A., there was no statistical significance. Therefore the filtration fraction was also nearly identical in both groups. The calculated value of RBF was also similar to others.
(B) The diluting capacity, as may be clearly defined by the value of positive free-water clearance, was not significantly different from others. (C) Both ADH-induced and dehydration-induced concentrating capacities tended to be lower in the Korean as compared to others reported in the U.S.A. and England. The maximum free-water extraction (T in I2o) was also less in the Korean than others. Furthermore, the urinary concentration of NaCl, as estimated by multiplying the chloride concentration by 2, accounted for approximately 2/3 of the total urinary, osmotic constituent in the Korean while it is less than 1/2 in others. As will be mentioned below, this is due to the fact that the urea reabsorption is greater in the Korean than others. (D) TMG was lower in the Korean than that reported in the U.S.A. (E) Although TmPAH tended to be higher in the Korean then that in the U.S.A. , there was no significant difference.
(F) When the urea/insulin clearance ratio was analyzed as a function of urine, plasma insulin concentration ratio, there was a distinct tendency for the former to be lower in the Korean than that in the U. S. A.
In summary, it may be emphasized that certain renal functions of the Korean are not identical to those reported in the literature, but are similar to those which are seen upon feeding a low protein diet. The fact that Korean people are living on a low protein diet may have an important, bearing in bringing about unique renal functions in the normal Korean.
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KEYWORD
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