The measurement of water, or volume, flow across renal tubules is required in various segments of the nephron in a variety of studies in which the quantification of water flow is the primary objective, but it is also required for studies in which solute movement is the focus. The rate of collection of the fluid emerging from the perfused tubule (the collectate) can be determined by collecting the fluid in calibrated pipets over timed intervals. The precision of this measurement depends on the proper construction of the pipet holding the collection end of the tubule as well as that of the pipets used to measure the volumes. Methods such as the microinulin determination used in micropuncture have been developed to measure the concentrations of volume markers chemically. The advantage of this method is that the electrode can be positioned within the holding pipet immediately adjacent to the fluid exiting the end of the tubule. Because the ratio of the emergent raffinose concentration to that in the perfusate should be directly proportional to the volume absorption rate, this provides a continuous measurement of the transepithelial volume flow.
ASJC Scopus subject areas
- Molecular Biology