5 MUCOSAL MAST CELLS IN THE BABY RAT JEJUNUM

Abstract

Mucosal mast cells (MMC) are found mainly within the jejunal submucosa. MMC increase in intestinal graft-versus-host reaction, and their degranulation is observed In parasitic enteropathy. Weaning is associated with morphological changes resembling those seen in mild cell mediated intestinal injury. We studied MMC in the young rat jejunum in relation lo weaning changes. Jejunal morphology, crypl cell production rate, intraepithelial lymphocytes (IEL) and goblet cells were studied, and MMC were counted in rat mast cell protease II antibody (anti-RMCP II) and toluidine blue stained sections. Serum RMCP II was determined with a direct ELISA method. In the next few days following weaning the jejunal villi shortened by about 30%. crypts elongated by the same amount, crypt cell production rate more than doubled, and the numbers of IEL showed a marked increase. The MMC counts showed a steady increase from birth to the time of weaning, sharp fall on the two days immediately after weaning, and further increase thereafter. Serum RMCP II level displayed a sudden rise at the time of weaning, with gradual decline thereafter. Mucosal mast cell degranulation, obviously associated with the event of weaning, may be responsible for the observed morphological changes through epithelial cell damage. Weaning is a period of temporary loss of oral tolerance in rats; this might be a result of jejunal injury caused by mucosal masl cell protease.