Inorganic mercury transport in the proximal tubule of the rabbit.

Abstract

Inorganic mercury transport was studied in the S1, S2, and S3 segments of the isolated perfused proximal tubule of the rabbit. The concentration of mercury in the perfusate was 18.4 microM. At this concentration all three segments of the proximal tubule underwent degenerative changes that proceeded to cellular necrosis at the end of the tubule which was attached to the perfusion pipet. This pathological process progressed along the tubule for approximately 200 microns. The remainder of the tubule, to the collection pipette, remained intact and free of any pathological changes. In examining the transport of mercury under these condition, it was found that, on average, the S1, S2, and S3 segments all removed inorganic mercury from the luminal fluid at approximately 140 fmol min-1 mm-1. The transport of mercury, as measured by the appearance of 203Hg in the bathing solution, was 80% lower than the removal of 203Hg from the luminal fluid. The mercury appearing in the bath could be accounted for by passive leakage through the necrotic portion of the tubule in the S1 and S2 segments, but not in the S3 segment. Leakage could account for only 16.2% of the transepithelial movement of inorganic mercury in the S3 segment. Inorganic mercury taken up by the tubule (92%) was primarily associated with the structural proteins of the tubular epithelial cells, while very little (8%) was found in the tubular extract. The toxicity of inorganic mercury was determined by titration. Perfusion with 1 microM inorganic mercury produced necrosis. The pathological features appeared to be the same as those resulting with 18.5 microM inorganic mercury.(ABSTRACT TRUNCATED AT 250 WORDS)