Microscopic methods for analysis of function in isolated renal tubules.

Using differential interference-contrast and fluorescence microscopy we have performed longitudinal observations of living, isolated and perfused nephron segments. With interference-contrast images we have made morphometric measurements (epithelial volume) and have compared those data to simultaneously measured physiologic parameters (delta psi T, Jv). Fluorescence images have allowed us to characterize qualitatively the distribution of a dye probe (acridine orange) within the epithelium and to follow changes in distribution in response to experimental maneuvers. In addition, preliminary results indicate that it should be possible to obtain quantitative information on the intracellular distribution of fluorescent probes, such as acridine orange, which have strong emission intensities. This should aid in the characterization of the cellular profiles of physiologic parameters such as pH or membrane potential. Collectively, these optical and physiological techniques should allow a meaningful analysis of structure and function in renal epithelia where a broad spectrum of transport processes can be examined.