Fibroblasts and eosinophils in normal fibroplasia of ferret vulval skin, shown by light and electron microscopy; with special reference to eosinophildegranulation

In order to compare aspects of normal fibroplasia with reports for patholog ically fibrotic tissue, light and electron microscopic observations were ma de on ferret vulval skin, which proliferates markedly with the onset of est rus and regresses equally fast after mating. Estrous tissue, which containe d hypertrophied fibroblasts, new collagen, elastic fibers and ground substa nce, was invaded by numerous eosinophils with extensive release of granules . Eosinophil degranulation was both extra- and intracellular; some cells, c ompletely disintegrated, had released all contents into the extracellular m atrix. Extruded granules reacted positively for major basic protein, In reg ression, diminished fibroblasts incorporated collagen fibrils, Many of the features seen in this normal fibroplasia in ferret vulval skin are similar to those in pathologic situations. Thus, in particular, the presence of deg ranulating eosinophils in pathologic fibrosis does not necessarily indicate that they are the cause of the disease. Our information and that from othe r sources implies a role for eosinophils in connective tissue change.