Reaction of the Rat Peritoneum to Acid Colloidal Pigments

Abstract

Albino rats were subjected to repeated injns. of various acid colloidal pigments (trypan blue, india ink, Biebrich''s scarlet, and Chlorazol black E). Subsequent changes in the peritoneum were then studied, principally from stained paraffin sections. Rat peritoneum reacts promptly to the presence of pigment particles by thickening and folding. The thickening is due to accumulation of free phagocytic and phagocytic-potential cells within the substance of, and deep to the peritoneum proper. Certain regions (diaphragm and mesentery) react more strongly than does peritoneum in general. Occasionally, there is considerable desquamation of mesothelium and escape of free cells into the peritoneal cavity. At no time do mesothelial cells appear to take part in phagocytosis. Localized collections of cells may appear, particularly within the mesentery; these collections form nodules visible to the naked eye. Histo-logically, the nodules are composed of a semi-fluid, necrotic center and a surrounding zone of dye-filled macrophages.