Mast cells of the bovine trachea: Staining characteristics, dispersion techniques and response to secretagogues

Sections of the lower trachea of cattle, fixed in either Carnoy's or formal in, were stained with toluidine blue, alcian blue, or alcian blue and safra nin O to study the mast cell population. After toluidine blue staining, abo ut twice as many cells in tissue fixed in Carnoy's contained dark blue gran ules compared with tissue fixed in formalin. In addition, for the first tim e in cattle, a population of cells containing red granules was identified a fter staining with alcian blue and safranin O. Most of these red granules w ere formalin sensitive. An enzymatic dispersal technique for mast cells is described that yielded 9.4 +/- 0.4 % mast cells (percentage of nucleated ce lls) with a viability of 92.3 +/- 0.6 %. Spontaneous histamine release was 3.3 +/- 0.8%. Dispersed mast cells were challenged with various immunologic al and nonimmunological secretagogues. The calcium ionophores, A23187, iono myocin, and BrX537A, were effective in releasing up to 94% of histamine in mast cells in a dose-response relationship. Pasteurella haemolytica culture supernate caused about 10% histamine release at a dose of 0.5 mg/mL after correction for spontaneous release. The average histamine content of the ma st cells was 6.6 +/- 1.0 pg/cell. Cytospins of dispersed cells fixed in Car noy's and stained with alcian blue and safranin O contained mast cells with blue and red granules, and a few cells with a mixture of both granule type s. Based on the effects of type of fixation, staining characteristics and h istamine content, a mix of subtypes of mast cells is present in the bovine trachea. However, functionally they respond to secretagogues differently th an rodent mast cells. Without an immunological secretagogue, studies to det ermine compounds that will be effective in blocking mast cell degranulation will be limited.