Abstract
Exogenous myoglobin was used as an ultrastructural tracer to study its uptake, concentration and movement in successive segments of the rat nephron. The presence of myoglobin reaction product in intercellular gaps of the capillary endothelium and in fenestrae of peritubular capillaries was also shown. Myoglobin was visualized by a diaminobenzidine-H2O2 reaction, taking advantage of its peroxidatic activity. Myoglobin may be revealed in situ in formaldehyde-glutaraldehyde-fixed tissue and may be useful as a low molecular weight protein tracer.