DOPAMINERGIC RECEPTORS AND ANGIOTENSINOGEN GENE-EXPRESSION IN OPOSSUMKIDNEY-CELLS

To investigate whether expression of the renal angiotensinogen gene is regulated by dopaminergic receptors, we used opossum kidney (OK 27) c ells with a fusion gene containing the 5'-flanking regulatory sequence of the rat angiotensinogen gene fused with a human growth hormone (hG H) gene as a reporter [pOGH, angiotensinogen nucleotide (N)-1498/+18], permanently integrated into their genomes. The level of expression of pOGH (angiotensinogen N-1498/+18) in OK 27 was evaluated by the amoun t of immunoreactive hGH (ir-hGH) secreted into the culture medium. In the absence of 3-isobutyl-1-methylxanthine (IBMX), addition of dopamin e (10(-13) to 10(-5) M) had minimal effect on the expression of the pO GH (angiotensinogen N-1498/+18) in 0K 27 cells. In the presence of IBM X, addition of low concentrations (10(-13) and 10(-7) M) of dopamine s timulated the expression of pOGH (angiotensinogen N -1498/+18) in OK 2 7 cells in a dose-dependent manner, whereas high concentrations (i.e., >10(-7) M) had minimal effect. The stimulatory effect of dopamine on the expression of pOGH (angiotensinogen N-1498/+18) was inhibited by t he presence of SCH-23390 (D-1-dopaminergic receptor antagonist) and sp iperone (D-2-dopaminergic receptor antagonist), but not by ketanserin (5HT(2)/5HT(1c)-serotonergic receptor antagonist). Moreover, the stimu latory effect of dopamine was inhibited by the presence of U-73122 (an inhibitor of phospholipase C and phospholipase A(2)) or staurosporine (an inhibitor of protein kinase C) or (R)-p-adenosine 3',5'-cyclic mo nophosphorothioate (Rp-cAMP[S]; an inhibitor of cAMP-dependent protein kinase A I and II). Addition of low concentrations (10(-13) to 10(-9) M) of SKF-82958 (D-1-dopaminergic receptor agonist) or PPHT (D-2-dopa minergic receptor agonist) also stimulated the expression of pOGH (ang iotensinogen N-1498/+18). The stimulatory effect of SKF-82958 was inhi bited by the presence of SCH-23390 or Rp-cAMP[S], whereas the effect o f PPHT was inhibited by the presence of spiperone or staurosporine. Th ese studies demonstrate that the expression of pOGH (angiotensinogen N -1498/+18) in OK 27 cells is modulated by dopaminergic receptor agonis ts.