THE ROLE OF MAST-CELLS AND HISTAMINE IN LEUKOCYTE-ENDOTHELIUM INTERACTIONS IN 4 RAT STRAINS

The objective of the present study was to determine the role of mast c ells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cro moglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observ ation that cromoglycate pretreatment only slightly influenced mast cel l degranulation in all strains except the Brown Norway. After mast cel l stabilization, only in Sprague-Dawley did topical administration of histamine (10(-4) M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Br own Norway strain. In conclusion, the hypothesis presented in other st udies, that degranulation of mast cells, and more specifically the rel ease of histamine, is of major importance for the induction of leukocy te-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency.