CHARACTERIZATION OF HUMAN AND RAT IMMORTALIZED CLONES OF PAROTID ACINAR-CELLS WITH RESPECT TO SPECIFIC PROTEINS AND THEIR MESSENGER-RNAS, AND RECEPTOR-LINKED ADENYLATE-CYCLASE

This study reports the isolation and characterization of a rat nontumorigenic parotid acinar cell clone (2RSG), a human nontumorigenic parotid acinar cell clone (2HPC8), and a human tumorigenic acinar clone (2HP(1)G). The levels of alpha-amylase mRNAs detected when using alpha-amylase cDNA of 1176 and 702 bp for hybridization were higher in 2RSG and 2HPC8 cells than their respective whole parotid glands. The level of these mRNAs decreased in 2HP(1)G cells. In contrast to alpha-amylase mRNAs levels, the alpha-amylase activity in cultured acinar tells was extremely low in comparison to whole glands, irrespective of species or cell status. The levels of proline-rich protein (PRP) mRNA and parotid secretory protein (PSP) mRNA detected when using PRP cDNA of 600 bp and PSP cDNA of 805 bp for hybridization were higher in 2RSG cells than those in rat parotid glands; the reverse was observed in 2HPC8 cells and human parotid glands. The levels of PRP mRNA and PSP mRNA in 2HPC8 and 2HP(1)G acinar cells were similar. The level of mRNA was not detectable in murine neuroblastoma cells (NBP2) using the same alpha-amylase cDNA, PRP cDNA and PSP cDNA for hybridization. The PSP level in rat parotid gland was lower than that found in 2RSG cells; the reverse was observed in 2HPC8 cells and human parotid glands. The level of PSP in 2HP(1)G cells was higher than that found in 2HPC8 cells. Isoproterenol increased the cAMP level in 2RSG, 2HPC8, and 2HP(1)G clones, being most effective in 2RSG cells, and least effective in 2HPG cells. Prostaglandin E(1) (PGE(1)) also increased cAMP level, being most effective in 2HPC8 cells and ineffective in 2HP(1)G cells, suggesting that the PGE(1) receptor-linked adenylate cyclase becomes inactive upon transformation. These results suggest that the three clonal acinar cells from rat and human parotid glands reported here can be useful in comparative studies on regulation of growth, differentiation, and transformation.