Abstract
There are three isoforms in Na/K-ATPase α subunit, α1, α2 and α3. It is known that α1 is expressed in wide range of cells/tissues and that α2 and α3 localize abundantly in neuronal tissues. We examined the expression of Na/K-ATPase α isoforms in salivary glands by RT-PCR. Alpha1 was expressed in three major salivary glands. Alpha2 was expressed in submandibular gland (SMG) and sublingual gland (SLG) and faintly parotid gland (PG). Alpha3 was expressed in SLG alone. The DNA sequence of α2 and α3 PCR products from salivary glands were identical with the corresponding portion of brain. We examined mRNA levels of these α isoforms by comparing the quantity of the PCR products. Alpha1 levels in 3 salivary glands were same as that in brain. Alpha2 levels in SMG, SLG and PG were determined to be 1/32, 1/16 and 1/256 of that in brain, respectively. Alpha3 level in SLG was at 1/8. Since α3 is abundant in nerve tissues, we examined whether α3 expression is induced when pheochromocytoma PC12 cells are differentiated into neuron-like cells by nerve growth factor (NGF). PC12 cells expressed α1 and α3, however α3 was not changed by the NGF-treatment of the cells. The α isoforms of HSY cells, a cell line of human parotid gland adenocarcinoma, were also examined. HSY cells expressed α1 alone. The expression pattern of Na/K-ATPase α isoforms in cells/tissues seemed to be rather stable and it was not easily altered with differentiation factors or carcinogenesis. [J Physiol Sci. 2006;56 Suppl:S123]
