Glucagon and insulin immunopositivity of mast cells in porcine gallbladder

It is well known that mast cells produce and release biologically active substances such as histamine, heparin, proteases, leukotrienes, cytokines, chemokines and growth factors. According to the available scientific literature on that topic this is the first time when gallbladder mast cells were found to have a capacity to produce insulin and glucagon. We aimed to perform an immunohistochemical study to determine glucagon- and insulin-positive mast cell existence and distribution in the wall of porcine gallbladder. The collocalisation of glucagon and insulin immunopositivity with metachromasy allowed us to detect the presence of glucagon and insulin immunoreactive mast cells in the bottom, body and neck of gallbladder. In addition, an immunohistochemical detection of tryptase as a better marker for mast cells than toluidine blue dye was used to compare the number of mast cells to glucagon and insulin immunoreactive cells. The ability of mast cells to produce hormones was confirmed by the chromogranin A immunopositivity of the same cells. The highest mast cell density was registered in in all layers of gallbladder’s neck, followed by the body and bottom of gallbladder. In conclusion, we established histochemically and immunohistochemically the localisation and density of two new types of mast cells: glucagon and insulin positive mast cells.