Stimulation of p-aminohippurate extraction in the maturing rabbit kidney

In vivo studies were performed to evaluate maturational changes in PAH extraction (EPAH) in the rabbit and to determine whether accelerated maturation of this process could be achieved. Fifty-four animals were injected with penicillin before study at 10, 14, 21, or 28 days of life. Forty-eight rabbits served as saline-injected controls. PAH extraction in controls increased from 29.3 +/- 2.4% at 10 days of age to 35.9 +/- 3.3% at 14 days, 59.7 +/- 3.5% at 21 days, 71.6 +/- 1.9% at 28 days, and 72.7 +/- 2.3% at 35 days of life. Penicillin injection on the 3 days before study resulted in enhancement of EPAH on days 10 and 14 to 42.7 +/- 2.4% and 65.0 +/- 3.2% (P less than 0.005). On days 21 and 28 less stimulation was noted (68.7 +/- 2.3%; 76.0 +/- 4.1%). Preinjection on days 6--9 with study delayed to day 14 also led to augmentation (46.7 +/- 3.7% P less than 0.05) but less than that achieved after injection on days 10--13. These data suggest that EPAH stimulation may be transient, descreases as maturation is approached and is likely related to substrate availability.