Mast cell density in domestic swine common hepatic duct

Detailed mast cell classification is reported in humans and rats, however such classification is not available in porcine common hepatic duct. It is interesting to find out whether mast cells in common hepatic duct are able to produce ghrelin, which is involved in a series of biological functions including regulation of food intake, body weight, gastrointestinal motility, hormone secretion, glucose release, cardiovascular functions, enzyme release, cell proliferation and reproduction in pigs. Because the determination of the cellular mechanisms responsible for normal and pathological biliary tract motility is difficult in humans, swine appears to be one of the most suitable animal model for physiological and morphological studies related to ghrelin peptide. The lack of information about the distribution of mast cells in the wall of common hepatic duct (Ductus hepaticus communis) in domestic swine motivated us to undertake this study in order to gain a better understanding of ghrelin peptide. The aim of this study was to define the localisation and number of tryptase-, ghrelin- and toluidine blue positive mast cells in the layers of porcine common hepatic duct. In this respect, the immunohistochemical staining for detection of tryptase and ghrelin expression was performed. The toluidine blue staining allowed the visualisation of metachromatic mast cells. The comparative study showed that tryptase positive cells were more numerous than metachromatic cells in all layers of the studied organ but the density of ghrelin positive cells was the highest. Tryptase immunohistochemistry allowed distinguishing ghrelin expressing mast cells from all ghrelin positive cells. The highest number of ghrelin positive cells indicated that not only mast cells but other cells also express ghrelin. The results allowed concluding that studied mast cell types had different density in the three main layers of common hepatic duct. The highest density of mast cells in the muscular layer and the possibility of mast cells to express ghrelin define its role in regulation of common hepatic duct motility and glandular secretion.