Thyroid hormone, L-T3, stimulates the expression of the angiotensinogen gene in cultured opossum kidney (OK) cells

Angiotensinogen (ANG) messenger RNA is expressed in opossum kidney (OK) proximal tubular cells. To examine whether thyroid hormone, L-T3, could stimulate the expression of the ANG gene in OK proximal tubular cells, fusion genes, consisting of various lengths of the 5'-flanking region of the rat angiotensinogen gene linked to a human growth hormone reporter gene, were constructed and introduced into OK cells. As a negative control, they were introduced into a nonkidney cell line, a human choriocarcinoma cell line (JEG-3). The level of the expression of fusion genes in these cells were determined by the level of immunoreactive human growth hormone secreted into the culture medium. The expression of ANG-growth hormone (ANG-GH) fusion genes pOGH (ANG N-1498/+18), pOGH (ANG N-688/+18), pOGH (ANG N-110/+18), pOGH (ANG N-53/+18), and pOGH (ANG N-35/+18) was 226-, 4.5-, 1.0-, 12-, and 2.5-fold higher than promoterless pOGH in the expression of growth hormone activity in OK cells. No significant expression of any of these ANG-GH fusion genes over the promoterless pOGH was observed in JEG-3 cells. The addition of L-T3 stimulates the expression of pOGH (ANG N-1498/+18) in a dose-dependent manner with a maximal and half-maximal effect at 10(-7) M and at 10(-8) to 10(-9) M, respectively. Thyroid hormone (10(-7) M) also stimulates the expression of pOGH (ANG N-688/+18) but not pOGH (ANG N-110/+18), pOGH (ANG N-53/+18), or pOGH (ANG N-35/+18).