Developmental changes in the renal capacity for sulfate reabsorption in the guinea pig

During growth, immature guinea pigs maintain a positive inorganic sulfate balance. In the present study, renal clearance techniques were used to determine the maximum renal capacity for sulfate reabsorption [TmRsi/glomerular filtration rate (GFR)] in three groups of guinea pigs at different stages of development (10-34 days, 35-80 days and greater than 120 days of age). These ages are comparable to infant, adolescent, and adult guinea pigs. The guinea pigs were weaned at 10 days and then maintained on normal guinea pig chow (0.13% sulfate). The TmRsi/GFR was determined by infusions of increasing concentrations of sulfate (0-16.8 mumol/min). TmRsi/GFR was significantly greater in young (infant and adolescent) than in older (adult) guinea pigs (2.20 +/- 0.26 mumol/ml and 1.80 +/- 0.27 mumol/ml vs 0.942 +/- 0.08 mumol/ml, P less than 0.05). These results demonstrate that the tubular capacity for inorganic sulfate reabsorption per milliliter of glomerular filtrate is enhanced in immature guinea pigs and decreases with age.