Renal brush border sodium-sulfate cotransport in guinea pig: effect of age and diet

Renal adaptation to changes in inorganic sulfate intake and age was studied by comparing sulfate uptake by proximal tubule brush border membrane vesicles (BBMV) from guinea pigs of different ages on relatively high- or low-sulfate diets. Adult (> 60 days) or young guinea pigs (< 25 days) were fed either a control diet (0.28% sulfur content), a sulfur-free diet, or a high-sulfate diet. After 5 days on the diet, BBMV were obtained and kinetic analysis of 35sulfate uptake was determined. In adult guinea pigs, the low-sulfate diet produced a significant increase in apparent maximal velocity (Vmax). In young guinea pigs, a lower sulfate intake did not appreciably increase Vmax, but a high-sulfate intake produced a reduction in Vmax. The affinity for sulfate (Km) was not changed in either age group. The dietary sulfate intake did not alter sodium gradient dependent-D-glucose or 32phosphate Vmax. In conclusion, our data indicate that renal inorganic sulfate BBMV uptake is regulated and responds to conditions of increased need (i.e., during the growth phase in young animals and during periods of decreased sulfate availability in adult animals) by increasing BBMV Vmax.