Abstract
During the past decade, freeze-fracture cytochemistry, the combination of freezefracture electron microscopy with cytochemistry, has greatly contributed to the investigation of the macromolecular architecture of biological membranes. The application of enzyme cytochemical labeling technique to freeze-fracture cytochemistry (i. e., freeze-fracture enzyme cytochemistry) has not received considerable attention although by enzyme cytochemical labeling technique many enzyme molecules can be labeled with metal cations and enzyme cytochemistry has been of great utility in cell biology studies. In this study, we report freeze-fracture enzyme cytochemistry: “label-fracture method” and “fracture-label method”. Freeze-fracture enzyme cytochemistry was applied to the study of acid phosphatase, 5′-nucleotidase in the proximal tubular epithelium of the rat kidney, ectoadenosine triphosphatase in human neutrophils and alkaline phosphatase in rat neutrophils, and was shown to be a technique that visualized these enzyme activities on replicas. Cerium as the capture agent was a useful enzyme cytochemical probe in this technique. Lead was applicable for labeling of plasma membrane-associated enzyme molecules. This technique leads to new applications that may extend the usefulness of freeze-fracture cytochemistry for the analysis of biomembrane structure.
