Endotoxin-Induced Mastitis in the Guinea Pig

Abstract

SUMMARY Histopathologic changes in the mammary glands of guinea pigs infused with Escherichia coli endotoxin are described. Inflammatory changes in the sinus papillaris and lactiferous sinuses were evident as early as 3 hours after inoculation of either endotoxin or physiologic saline solution (pss). There was apparently little effect on mammary parenchymatous tissue until 6 hours. Massive infiltration of neutrophils into the alveoli was noticed 12 hours after endotoxin was inoculated; however, slight inflammatory changes were also seen in pss-treated glands. Cloudy swelling, hyaline droplet degeneration of the alveolar epithelial cells, and thick proteinaceous material enmeshed with neutrophils and cellular debris in the alveoli and lactiferous ducts were the most significant changes observed in the gland. There was hyperplasia of the inguinal lymph nodes, as well as moderate enlargement and congestion. Marked leukopenia was observed in mastitic guinea pigs and was primarily due to neutropenia and lymphopenia. Signs of toxemia, such as fever, increased heart rate, muscular tremors, central nervous system depression, aphagia, and adipsia, were observed. Grossly, at the 12th postinoculation hour, there was no evidence of galactopoiesis, and hyperemia of the subcutaneous tissues around the mammary gland was seen.