REN and polycythemia: Kim et al. reported that angiotensin II (ATII) increases Epo production via angiotensin 1 receptor (AT1R)-mediated early growth response-1 (Egr-1) activation in human renal 786-O cells [12,13] Kato et al. reported that transgenic mice having renin and angiotensinogen genes exhibit erythrocytosis and that knockout mice lacking renin and angiotensinogen exhibit anemia [14,15].