Enzymatic differentiation of arterial and venous segments of the capillary bed during the development of free muscle grafts in the rat.
The revascularization of freely grafted muscles in the rat was studied by histochemical reactions that on frozen sections stain the arterial part of the capillary bed blue (alkaline phosphatase [AP] reaction) and the venous part of the capillary bed red (dipeptidyl peptidase IV [DPP IV] reaction). In 112 rats the extensor digitorum longus or soleus muscles were freely grafted and removed at various times up to 93 days following the surgery. In cross section, the capillaries of a normal muscle show a mosaic pattern of staining for the activity of the two enzymes. After grafting, DPP IV activity of capillaries is lost throughout the entire graft within a day or two; but within ischemic muscle, weak and diffuse AP staining persists in capillary remnants for up to 6 days. In the very periphery of the graft AP staining is also preserved in partially damaged capillaries. By 4 days, new AP-positive capillaries can be identified at the periphery of the graft, and in succeeding days AP-positive capillaries are found progressively nearer the center of the graft. At 7 days, the capillary/muscle-fiber ratios are 66% of normal in the periphery of the graft and 44% in the intermediate zone. DPP IV-stained capillaries are not seen until 7 days after grafting. By 60 days, when the grafts have become stabilized, the mosaic pattern of capillary staining has become reestablished. In mature grafts, the number of capillaries per unit area was slightly higher than that in control muscles, but the capillary/muscle-fiber ratio was slightly lower, owing to the smaller than normal cross-sectional areas of the regenerated muscle fibers.
D000818:Animals; D001158:Arteries; D002196:Capillaries / Q000201:enzymology; D005260:Female; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000637:transplantation*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D014680:Veins