Factors affecting the maturation of renal PAH extraction in the new-born dog

摘要

1. The maturation of renal para-amino-hippurate extraction (EPAH) was studied in thirty-nine mongrel new-born dogs aged 2-29 days. EPAH was also measured in five adult dogs for comparison.2. There was no apparent change of PAH extraction during the first month of life but EPAH was lower in the puppy than in the adult. Under mannitol diuresis EPAH averaged 0·49 for the puppies and 0·83 for the adult dogs (P < 0·001). EPAH averaged 0·48 for the puppies under nondiuretic conditions, a value not significantly different from that observed during mannitol diuresis. There was no correlation of EPAH with mean arterial blood pressure.3. Inulin extraction (EIn) remained constant during the first month of life and was the same in the new-born and adult dog suggesting that preglomerular shunting of plasma away from functioning nephrons was the same for both the puppy and adult dog.4. EPAH did not change in the puppy when plasma concentrations varied from trace (using [³H]PAH) to 0·25 mM indicating that excessive PAH load is not a factor in the low EPAH of the puppy.5. Diffusion of PAH from the red blood cell was excluded as an explanation for the low EPAH since diffusion was the same for both the adult and new-born dog.