SPECIES-DIFFERENCES IN THE EXPRESSION OF TRANSFORMING GROWTH-FACTOR-ALPHA (TGF-ALPHA) IN THE SUBMANDIBULAR-GLAND AND PANCREAS

Conclusion. Significant differences exist in the expression of transfo rming growth factor-alpha (TGF-alpha) in the submandibular glands (SMG ) and the pancreas of different species and among cell components in t he same species. Background. Our previous studies have shown marked di fferences in the expression of TGF-alpha in the pancreas of humans and Syrian hamsters. To examine whether these differences also exist in o ther species, we examined the expression of TGF-alpha in the pancreas of mouse, rat, Syrian hamster, guinea pig, rabbit, pig, dog, and monke y. We included the SMG of these species for comparison. Materials and Methods. The formalin-fixed tissues of these species (n = 3) were inve stigated by immunohistochemistry using a monoclonal antibody to TGF-al pha. The SMG of rat, mouse, hamster, rabbit, pig, dog, and monkey were examined by RT-PCR to assure the specificity of the antibody. Results . Remarkable species differences were found in the expression of this peptide in both the SMG and the pancreas. In the SMG, the expression v aried in different cell components, even in the same tissue of the spe cies. Although excretory and secretory ducts of the SMG of most specie s reacted with the antibody, intercalated ducts were immunoreactive on ly in mouse and guinea pig. Acinar cells were either weakly positive o r nonimmunoreactive. In the pancreas of most species, the cells of the large and medium-sized ducts expressed TGF-alpha, whereas centroacina r cells of only rat and dog reacted with the antibody. Marked differen ces were found in the expression of TGF-alpha in islet cells and in it s spatial distribution. Differences were also found in the immunoreact ivity of mesenchymal and neural cells among the species.