AJP - Gastrointestinal and Liver Physiology, Vol 244, Issue 6 630-G636, Copyright © 1983 by American Physiological Society
Uptake of iopanoic acid by isolated rat hepatocytes in primary culture
J. L. Barnhart, B. L. Witt, W. G. Hardison and R. N. Berk
Uptake of iopanoic acid (IOP) was studied in 3-day primary cultures of rat
hepatocytes isolated by the collagenase perfusion method. 125I activity of
cells after incubation with 125I-IOP (1.0-100 microM) was used as a measure
of uptake. At each IOP concentration uptake was linear for the first 45 s.
The initial uptake velocity was directly proportional to IOP concentration
and was nonsaturable up to 100 microM. The calculated uptake rate constant
was 0.67 nmol . mg prot-1 . min-1 . microM-1. Uptake was only slightly
reduced when the incubation was performed at 4 degrees C and was
independent of sodium concentration. Albumin in the medium reduced IOP
uptake. Uptake, however, was always greater than that predicted from the
unbound IOP concentration alone. The data indicate that the hepatocyte
uptake of IOP occurs by both a passive process and a saturable process. The
saturable uptake component depends on an albumin-IOP-hepatocyte
interaction. The influence of albumin on uptake occurs possibly by an
undefined specific cell surface phenomenon of albumin that promotes uptake
of IOP or by enhancement of the diffusibility of IOP across the unstirred
layer.
