The change of p-aminohippuric acid disposition kinetics accompanied by growth in mice.

The change of disposition kinetics for p-aminohippuric acid (PAH) was studied following intravenous administration of p-[glycyl-1-14C]aminohippuric acid to 1-day-old, 1-week-old, 3-week-old and 8-week-old mice. The expiratory excretion of 14CO2 in 24 h following the administration was almost negligible in 1-day-old and 1-week-old mice in contrast to 3-week-old (6.8 +/- 1.8%) and 8-week-old (8.8 +/- 1.9%) mice. The ability to metabolize PAH may not be developed in these infant mice. The elimination of blood radioactivity following the administration was considerably delayed in 1-day-old and 1-week-old mice, especially in 1-day-old mice, suggesting that the renal tubular secretory function for PAH might not have been developed in the infant mice. Whole-body autoradiographic data showed that the transfer of PAH from blood to muscle was enhanced in 1-day-old and 1-week-old mice, especially in 1-day-old mice, compared to 3-week-old and 8-week-old mice. The enhanced muscular cell membrane permeability to PAH in 1-day-old and 1-week-old mice was considered to be the most plausible explanation for this result.