Macrophages in the omentum: Effects of drugs and pertussis vaccine evaluated by a simple weight assay

Abstract

Mineral oil was injected into the peritoneal cavity of rats. Two weeks later, the omentum was dissected free of pancreatic tissue in a systematic manner. The weight of the omentum increased two- to threefold due to accumulation of a relatively pure population of oil-laden macrophages. A shorter time period gave a smaller weight increment and a longer interval favored development of fibrous connective tissue. Old animals were unsatisfactory subjects because of the excessive and very variable amounts of fat in the omentum. The weight of the macrophage-laden omentum was used as a simple assay for the delivery and phagocytic functions of the monocyte-macrophage system. Systemic administration of pertussis vaccine or cycloleucine inhibited the accumulation of macrophages in the omentum. Inoculation of oil and weighing of the omentum in the course of routine screening and toxicological testing of drugs could add important information with hardly any extra effort or expense.