The influence of sampling technique on the micropuncture determination of GFR and reabsorptive characteristics of single rat proximal tubules

Summary Studies have been carried out in order to assess the validity of the determination of the single nephron filtration rate by micropuncture techniques. By means of a double microscope and two investigators operating simultaneoulsy, intratubular pressure and single nephron transit time were recorded during sampling. The data indicate that collection of tubular fluid by means of aspiration significantly accelerates transit time, decreases intratubular pressure, and results in an increase of single nephron filtration rate. In contrast, spontaneously flowing collections were associated with insignificant alterations of transit time and intratubular pressure. Technical details underlying these observations have to some extent been delineated. The importance of these data with respect to artifactual alterations of single nephron parameters is discussed.Supported by a Medical Research Fellowship of the Medical Research Council fo Canada.