AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 2 195-G200, Copyright © 1987 by American Physiological Society
Alterations in protein transport events in rat liver after estrogen treatment
M. A. Goldsmith, A. L. Jones, B. J. Underdown and J. M. Schiff
The effects of 17 alpha-ethynylestradiol (EE) treatment on the hepatic
processing of rat polymeric immunoglobulin A (IgA) and human
asialoorosomucoid (ASOr) were studied. After 5 days of treatment with EE (5
mg/kg) or solvent alone, male rats were anesthetized and injected with
tracer doses of the test proteins. Bile flow rates had been reduced by
greater than 60% in the EE-treated animals. A previously reported
radiolabeling strategy was used to monitor both the transport of intact
protein to bile and the degradation of protein in lysosomes. Transport of
intact IgA to bile was reduced by 43%, with transport peaking 27 min later
in EE-treated animals compared with controls. There was a corresponding
impairment of uptake of labeled IgA from blood. EE induced no kinetic
change in the uptake or processing of ASOr. However, there was an increase
in the proportion of ASOr reaching bile intact from 3% to 15-23% of the
injected dose. The data indicate that EE disables the transport pathway for
IgA and causes a partial change in the routing of ASOr after endocytosis in
favor of direct transport to the bile canaliculus. These findings may have
implications for the importance of membrane composition in protein
transport events.
