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D-Glucose; Microperfusion; Proximal Tubule; Active Reabsorption; Kinetic Study
Abstract:
The proximal convoluted tubule of rat kidney was continuously perfused with a steady state solution containing 0.5 to 2.0 mM of D-glucose. The gradual decrease of intraluminald-glucose concentration was investigated with repeated collections of perfusate from the same tubule whereby the sequence of punctures proceeded towards the site of perfusion. The rate of D-glucose transport per unit area decreased with decreasing intraluminald-glucose concentration. This relationship could be expressed by a two parameter system corresponding to the Michaelis-Menten equation. It was found that the local maximal transport rate Vmax equals 6×10−10 mol×cm−2×sec−1 and Km equals 0.6 mM.
Our data on active resorption and passive permeability ofd-glucose in the proximal convolution have been subjected to computer analysis. The sum of both components ofd-glucose transport alone as measured under the condition of zero netflux of sodium chloride and water did not match the amount of net glucose transport found for the whole kidney under free-flow-conditions.
