Comparative studies of mast cells from normal (non-immunized) and actively sensitized dogs.

Morphologically and functionally intact mast cells were isolated from the lung and mesentery of normal or actively sensitized dogs using the pronase or collagenase tissue dissociation methods. The latter method yielded about 6 times as many metachromatically staining cells. Electron microscopic examination revealed the presence of both mast cells and basophils in all samples, independent of the enzyme used for tissue dissociation. The average histamine content of the cells obtained with the pronase method was significantly higher (21.8 +/- 3.1 pg) than after collagenase treatment (16.2 +/- 4.2 pg). There was no appreciable difference in the reactivity to secretory stimulation of the cells obtained by the two methods. The cells isolated from actively sensitized dog tissues showed a significantly higher spontaneous histamine release (12.9 +/- 1.2%) than those from non-sensitized animals (7.8 +/- 1.3%) and responded equally well to challenge with both the antigens ovalbumin and horse serum. In contrast to those from normal animals, the mast cells from actively sensitized dogs released histamine on stimulation with acetylcholine, metacholine or atropine. In addition, the response to the threshold concentration of compound 48/80 (10(-6)) was significantly stronger in the sensitized cells. Small molecular polyvinylpyrrolidone (K25) was effective in mast cells from normal and actively sensitized dogs.