Renal handling of lead in dogs: clearance studies
Vander, A.J.; Taylor, D.L.; Kalitis, K.; Mouw, D.R.; Victery, W.
American Journal of Physiology 233(6): F532-F538
1977
ISSN/ISBN: 0002-9513 PMID: 596452 Document Number: 112515
Whether acutely administered Pb undergoes glomerular filtration, tubular reabsorption or tubular secretion was studied. Renal clearance studies of the handling of acutely administered 203Pb (with and without carrier Pb) were performed on pentobarbital-anesthetized dogs. The concentration of ultrafilterable plasma Pb (PbUlt) was estimated with Amicon filter cones having a MW cutoff of 50,000; no anticoagulants were used. To protect against possible artifacts secondary to the injection schedule, 203Pb was administered in 2 ways: either as a single injection (protocol I) or as a constant infusion (protocol II); both protocols produced qualitatively similar results. PbUlt was 22-25% of total plasma Pb when only carrier-free 203Pb was given, but it was 11-12% when additional cold Pb was administered. In only 1 of 42 clearance periods in 14 dogs was the PbUlt clearance (CUlt-Pb) greater than creatinine clearance [CCr]. For all carrier-free experiments, the ratio CUlt-Pb/CCr was 0.69 .+-. 0.16 in protocol I and 0.29 .+-. 0.05 in protocol II. The addition of cold Pb resulted in lower clearance ratios, going as low as 0.06 and 0.11. Neither furosemide for mannitol altered Pb excretion. Following acute administration of Pb, a significant fraction of plasma Pb is ultrafilterable, and a large fraction of the filtered Pb undergoes tubular reabsorption. The results provide no direct evidence for tubular secretion of Pb. The relevance of this filtration-reabsorption mechanism for the renal handling of chronically assimilated Pb is discussed.