Specific identification of hemoglobin and myoglobin in renal tubular casts by the fluorescent antibody technic on fixed embedded tissues.

Hemoglobin and myoglobin have been identified in formalin-fixed paraffin-embedded sections of human autopsy material with the indirect fluorescent antibody technic. The sensitivity and specificity observed were comparable to those reported by other investigators who used fresh-frozen sections. When this approach was applied to archival autopsy tissue, it was possible to identify some pigmented renal tubular casts specifically as myoglobin or hemoglobin and to separate them from other pigmented casts such as bile or melanin. The data suggested that the hemeproteins, as they pass along the nephron, are progressively denatured, and that their reactivities with specific antisera, iron stains, and peroxidase substrates are altered. Intact hemeprotein molecules react with specific antibody and show peroxidase activity, but the iron is not demonstrable by traditional methods. In the proximal tubules, after filtration, they react with specific antibody, show peroxidase activity, and also have demonstrable iron. By the time they reach the collecting tubules, they show only peroxidase activity.