Abstract

Mast cells are known to play a critical role in asthma, allergy, and inflammation. Although the guinea pig has been widely used as an experimental animal to study mast cell function in these conditions, little is known about repopulation and maturation of guinea pig mast cells in vivo. The present study was undertákcn to characterize the maturation and repopulation of guinea pig mesenteric mast cells following intraperitoneal injection of distilled water. In uninjected animals, mesenteric mast cells can be found lying adjacent to blood vessels in the fat sheaths and throughout the windows of the mesentery. By 24 hours after distilled water injection, the mesenteric mast cells appeared lysed with many granules lying free in the extracellular matrix. At 3 days after injection, the mesentery was almost! devoid of mast cells. A few immature cells could be found associated with the blood vessels in the fat sheaths. By 5 days, mast cells were found not only adjacent to the blood vessels but bul also in the mesenteric windows. Duríng this initial stage of repopulation of the mesentery, a very immature mast cell lying along the blood vessels in the fat sheaths was also identified by electrón microscopy. On day 7, the appearance of the mast cells in the mesentery was similar to that seen in control ani­máis. The repopulation and maturation of guinea pig mesenteric mast cells in vivo was similar to that previously reported for rats but differed in the lime course of the disappearance of the guinea pig mast cell granules and the appearance of immature mast cells.