Metabolic acidosis regulates rate renal Na-S(sub i) cotransport activity

The effect of metabolic acidosis (MA) on Na-S(sub i) cotransport activity and NaS(sub i)-1 protein and mRNA expression was investigated. In rats with MA for 24 hrs, there was substantial increase in the fractional excretion of S(sub i), which was related with a 2.4-fold reduction in brush-border membrane (BBM) Na-S(sub i) cotransport activity. Results showed that MA decreases S(sub i) reabsorption by inducing reductions in BBM Na-S(sub i) cotransport activity and that reductions in the expression of NaS(sub i)-1 protein and mRNA abundance, at least partially, have a significant role in the inhibition of Na-S(sub i) cotransport activity during MA.