Effects of acid feeding on urinary excretion in Tg/Tg:ET_B^+/+ and Tg/Tg:ET_B^–/– mice. Urine was collected from Tg/Tg:ET_B^+/+ and Tg/Tg:ET_B^–/– mice at baseline and after 7 days of acid ingestion. Samples were analyzed for (a) ammonium, (b) pH, (c) citrate, (d) phosphate, and creatinine concentrations. Urinary ammonium, citrate, and phosphate excretion are expressed as the ratio of their respective urinary concentrations to the creatinine concentration measured on the same sample. Ammonium: control, n = 19; acid, n = 8. Urine pH: control, n = 21; acid n = 10 (Tg/Tg:ET_B^+/+), n = 9 (Tg/Tg:ET_B^–/–). Citrate: control, n = 14 (Tg/Tg:ET_B^+/+), n = 15 (Tg/Tg:ET_B^–/–); acid, n = 7. Phosphate: control, n = 14 (Tg/Tg:ET_B^+/+), n = 15 (Tg/Tg:ET_B^–/–); acid, n = 7. ^AP < 0.05.