Modulation of the mitotic activity and population of the mast cells in the oral mucosa by substance P.

To assess the effect of substances inducing mast cell degranulation (substance P and granuliberin R) on the mitotic indices of the gingiva stratified epithelium, basal cells from rats were studied in vivo. Seventy Lewis male rats were used in the study. The rats received injections of either 0.1 ml 0.9% NaCl (l0 rats), or substance P (10(-4), l0(-6), 10(-8) g/ml) (30 rats), or granuliberin R (10(-4), l0(-6), 10(-8) g/ml) (30 rats) into their mandibular gingiva in the vicinity of the right mental foramen. The mitotic index of keratinocytes was established after the kolchicine arrest (2 hours prior to material collection i.p. injection). The number of cells in metaphase was counted on 1000 consecutive basal layer cells after hematoxilin and eosin section staining. Mast cells were revealed using pinocyanol erythrosinate according to Bensley. Numerical density and morphometric features were analyzed. Substance P and granuliberin R injected into the gingiva affect the mast cells and the basal cell proliferation of the gingival epithelium. The diminished mitotic activity of basal layer cells was accompanied by degranulation and/or migration of mast cells under the basal membrane of the epithelium. After administration of high doses of granuloliberin R, mast cells were found in the deep connective tissue alligned towards the epithelium. A neuromediator from the trigeminal nerve (substance P) and substances from mast cells actively interfere in the proliferation of oral keratinocytes and the activity of connective tissue cells.