AJP - Gastrointestinal and Liver Physiology, Vol 248, Issue 6 663-G669, Copyright © 1985 by American Physiological Society
Preferential binding of vasoactive intestinal peptide to hepatic nonparenchymal cells
D. F. Gardner, M. S. Kilberg, M. M. Wolfe, J. E. McGuigan and R. I. Misbin
The binding of 125I-vasoactive intestinal peptide (125I-VIP) and
125I-insulin has been examined in highly enriched populations of rat
hepatocytes and hepatic nonparenchymal cells. 125I-VIP bound to
high-affinity sites (Ka = 1.7 X 10(9) M-1) in nonparenchymal cells.
Specific binding in these cells was nearly fivefold greater than in
hepatocytes (15.0 +/- 0.6% vs. 3.6 +/- 0.7% radioactivity bound per 4 X
10(5) cells). In contrast, 125I-insulin binding was similar in both cell
populations (18.2 +/- 2.4% per 4 X 10(5) cells in hepatocytes vs. 17.1 +/-
1.0% in nonparenchymal cells). Glucagon and insulin had no effect on
125I-VIP binding in nonparenchymal cells. Secretin inhibited 125I-VIP
binding but was only about 1% as potent as unlabeled VIP. VIP had no
apparent effect on cAMP levels in either cell population, whereas glucagon
increased cAMP levels in both cell types. Our findings suggest that VIP
binds preferentially to hepatic nonparenchymal cells and that these cells
are primarily responsible for the clearance of VIP from the portal
circulation.
