Proximal tubular stop flow pressure: an index of glomerular capillary pressure?


Central to the assumption that glomerular capillary pressure (P gc) can be equated with the sum of arterial oncotic pressure (π art) and the pressure in a blocked proximal tubule (“stop flow” pressure, P sf) is that filtration ceases in the blocked nephron. Should filtration not cease, but continue at a rate equal to tubular reabsorption between the block and the glomerulus, P sf, for a given P gc, will depend on the distance between block and glomerulus. This would have serious consequences for the interpretation of P sf, particularly in respect of its frequent use in analysis of the tubuloglomerular feedback (TGF) mechanism. Experiments were performed in anaesthetized Wistar rats to examine whether a length dependency of P sf exists and, if so, to what extent this relationship alters during maximal TGF stimulation by loop of Henle perfusion. A length dependency of P sf existed both in the absence and presence of loop flow. The regression coefficients were significantly different from 0 and from each other. P gc cannot thus be equated with the sum of P sf and π art. The length dependent error in P sf makes it unsuitable for the quantitative analysis of TGF and glomerular haemodynamics.

DOI: 10.1007/BF00370991

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Cite this paper

@article{Davis1990ProximalTS, title={Proximal tubular stop flow pressure: an index of glomerular capillary pressure?}, author={John M. Davis}, journal={Pfl{\"{u}gers Archiv}, year={1990}, volume={417}, pages={264-268} }