The measurement of glomerular filtration rate in single nephrons of the rat kidney.

Perlhaps nowlhere in the broad spectrum of present-day renal plhysiology studied with micropunctuire teclhniques lhas there occurred a greater nor more damaging erosion of confi(lence in the interpretation of results than in the area pertaining to the measurement of glomerular filtration rate (GFR) in single neplhrons. In large part, this decline in confidence can be traced to a recent series of reports claiming eitlher that free-flow aspiration teclhniques may, by inducing large reductions in intrattubular pressure, serve to spuriously enlhance net filtration pressure and filtration rate(l,2), or that the recollection tecliimique per se may intluce sptirious and often considerable elevations in neplhron GFR(3). This report reviews the results of a recent series of experimnents in rats undertaken by Us to evaluate the extent, if any, to wlhiclh metlhodologic influences contribute to systematic alterations in free-flow esimates of single nephron function.