Summary
In order to test the applicability of the occlusion time method for measuring the reabsorptive characteristics in the proximal convolution of the rat kidney, a quantitative analysis of this method was performed. The time course of decrease in tubular diameter, following interruption of GFR, was measured from time sequenced photomicrographs taken before and during the period of occlusion. Tubular occlusion, as measured by direct microscopic observation or by extrapolating the initial slope of decrease in luminal diameter to zero diameter, was found to be constant over a range of GFR from 0.3–2.2 ml/min · g kidney weight. A positive correlation was observed between GFR and free flow luminal diameter. The decrease in luminal diameter, which occurs during the period of occlusion, is a linear function of time.
The results indicate that the lateral water flux is directly related to the free flow luminal diameter prior to the period of occlusion, i.e., to GFR. In contrast, the lateral water flux remains constant during the decrease in luminal diameter, which occurs during the period of occlusion. Although the results are consistent with the assumption of a glomerular-tubular balance in the proximal convolution, the absolute values for lateral water flux, as measured by the occlusion method, are approximately twice as high as values calculated from free flow micropuncture experiments, split droplet experiments, and cinematographic experiments.
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Supported by the Deutsche Forschungsgemeinschaft and the US Department of the Army, through its European Research Office.
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Wahl, M., Nagel, W., Fischbach, H. et al. On the application of the occlusion time method for measurements of lateral net fluxes in the proximal convolution of the rat kidney. Pflügers Archiv 298, 141–153 (1967). https://doi.org/10.1007/BF00364694
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DOI: https://doi.org/10.1007/BF00364694