The effect of methylprednisolone on the postnatal maturation of taurocholate transport was studied by using isolated ileal brush border membrane vesicles. Vesicles were prepared from 14-day-old control, 14-day-old methylprednisolone-treated, and untreated 21-day-old rats. Methylprednisolone treatment resulted in a significant stimulation of taurocholate uptake by an inwardly directed Na+ gradient when compared with a choline gradient incubation. These differences occurred at 20 seconds and 1, 2, and 5 minutes of incubation (P less than 0.05). In 14-day-old controls, uptake was similar for Na+ and choline gradients. A plot of active uptake velocity vs. taurocholate concentration (0.1 to 1.0 mmol/L) in 14-day-old controls was linear and approached the abscissa, indicating the absence of active transport. Plots for methylprednisolone-treated rats showed saturability. An inwardly directed Na+ gradient stimulated initial taurocholate uptake rates by twofold at 37 degrees C (P less than 0.01), but not at 4 degrees C. Glycocholate and glycodeoxycholate inhibited Na+-stimulated taurocholate uptake by 50% (P less than 0.01) and 20% (P less than 0.05), respectively. These data indicate that pharmacologic doses of methylprednisolone accelerate the postnatal acquisition of Na+-dependent taurocholate cotransport in rat ileal brush border membranes.