Time course and vectorial nature of albumin metabolism in isolated perfused rabbit PCT
The time course and vectorial nature of renal metabolism of albumin (Alb) were studied. The tubular absorption, accumulation, and hydrolysis of Alb and the release of the hydrolysis products were determined in the isolated rabbit proximal convoluted tubule (PCT) perfused with tritiated Alb ((/sup 3/H3C)Alb) at 36.4 micrograms/ml. The Alb absorption across the apical membrane was constant (99.9 +/- 4.9 x 10(-3) ng.min-1.mm-1). In contrast, the accumulation and hydrolysis of Alb in the cells increased nonlinearly with time. The bulk of the tritium that accumulated in the cells was associated with intact (/sup 3/H3C)Alb. Only the final hydrolysis products were released from the cells and these first appeared in the peritubular bath 6-7 min after the start of perfusion of the tubule with (/sup 3/H3C)Alb. The hydrolysis product was not detectable in the tubule lumen. The proteolytic activity correlated linearly with the protein load to the cells, characteristic of first-order kinetics and a high-capacity system. The results suggest that the renal tubular handling of proteins proceeds from the apical to the basolateral aspect of the cell. The transcellular processing of Alb is rapid and can occur in 6-7 min. The accumulation of intact protein in the cell and the first-order kinetics of hydrolysis of the absorbed protein suggest that the rate-limiting step in proximal tubular handling of proteins may include the initial hydrolysis of protein or reside in steps that precede the hydrolysis.
- Research Organization:
- Univ. of Florida College of Medicine, Gainesville (USA)
- OSTI ID:
- 6735958
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 255
- Country of Publication:
- United States
- Language:
- English
Similar Records
Transport of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine, a metabolite of trichloroethylene, by mouse multidrug resistance associated protein 2 (Mrp2)
Luminal and basolateral uptake of insulin in isolated perfused, proximal tubules
Related Subjects
ALBUMINS
METABOLISM
CELL MEMBRANES
IN VITRO
PERFUSED TISSUES
RABBITS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TUBULES
ANIMAL TISSUES
ANIMALS
BODY
CELL CONSTITUENTS
ISOTOPE APPLICATIONS
KIDNEYS
LABELLED COMPOUNDS
MAMMALS
MEMBRANES
ORGANIC COMPOUNDS
ORGANS
PROTEINS
TISSUES
VERTEBRATES
550501* - Metabolism- Tracer Techniques