Rats received acute systemic NO synthesis inhibition (NOSI) alone, with NMA (group I), combined endothelin blockade of ETA and ETB receptors and NOSI with bosentan and NMA (group II), combined NOSI and angiotensin II AT1 receptor blockade with losartan and NMA (group III), and NOSI during combined ETA, ETB, and AT1 receptor blockade (group IV). The asterisk denotes a significant difference in the response versus NOSI alone.