On the Renal Excretion of Xylose 1

Abstract

The excretion of xylose has been investigated as a further application of the method of analysis which we have already applied to the excretion of ingested creatinine (1). The method consists in analyzing separately the time change in the rate of excretion by the kidney and in the plasma concentration, after the initial disturbance produced by the rapid absorption of creatinine and its distribution in the body fluids has subsided. It was found that, in the case of creatinine, both the rate of excretion and the plasma concentration diminish exponentially in the course of time, the two functions being asymptotic to their pre-ingestion values, and furthermore, that the coefficients of the time in both exponentials are equal, on an average. Under these conditions, it was proved that the elimination of the time between pairs of simultaneous equations yields a linear relation between the rate of output and the instantaneous concentration in the plasma. It was also proved that the method provides the means of determining the errors of observation. After the constants had been calculated and the errors of observation taken into consideration, it was shown that practically all the variation in the ratio of the rate of output to the plasma concentration (called glomerular filtration rate (2) or creatinine clearance (3) ) could be accounted for.The growing literature on xylose has prompted us to study the excretion of this substance by the same method. The same interpolating functions have been found to hold as in the case of creatinine, namely, simple exponential functions of the time, asymptotic to the pre-ingestion blank levels. The only difference in the behavior of the two substances, outside the values of the constants, is that the exponential phase of decrease in plasma concentration (x) and rate of output (y) begins somewhat later after the ingestion of xylose than after creatinine. The two exponential curves will be referred to as the x curve and the y curve respectively.

The Use of Inulin Clearance as a Measure of Glomerular Filtration

“…and 100 mg./100 ml., using the single injection and infusion methods, show considerable resemblance to the results obtained by many workers with exogenous creatinine [Winkler and Parra, 1937;Findley, 1938;Cope, 1931;Dominguez and Pomerene, 1934]. This extends to the phenomenon, not included in the results presented earlier in this paper, of a rise in the clearance of inulin following a second injection of the substance.…”

Kinetics of Drug Absorption, Distribution, Metabolism, and Excretion

“…The disappearance of galactose after intravenous injection was another interesting case studied by Dominguez and Pomerene (22). Excretion rate was directly proportional to plasma concentration, but plasma concentration did not decrease exponentially.…”

“…Other work by Dominguez and Pomerene has been the development of a method to calculate absorption rate following oral ingestion of drug and the application of the method to creatinine (23). In the terminology used in this review, the equation developed was 185 derived the appropriate expressions to describe amount-time courses of drug in blood and tissues, as well as inactivated and excreted amounts under this condition of administration.…”

“…Lapp has also published a number of papers concerned with other general or specific aspects of the subject of this review (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51). For the most part, the kinetics of substances studied by Lapp were describable by the kinetics of Dorninguez (10)(11)(12)(13)(14)(15)(19)(20)(21)(22)(23)(24) and/or Teorell (3). Since, in almost all cases, the materials studied by Lapp were drugs as such, rather than physio-…”

“…23) where k2 was the elimination rate and k1 the absorption rate. This equation assumes instantaneous attainment of equilibrium between drug in blood and drug in other fluids o f distribution.…”