Detection of a receptor for angiotensinogen on placental cells.
BACKGROUND
Current evidence indicates that there may be a tissue-specific renin-angiotensin system (RAS) in the human placenta. To better define the placental RAS, this study sought to determine whether placental derived cells possessed a receptor for angiotensinogen (AGT), a rate limiting component of the RAS.


METHODS
A human placenta-derived cell line, CRL-7548, a highly purified AGT and iodine-125-labeled angiotensinogen ((125)I-AGT) were used in this study. The cells were seeded in 35-mm diameter plastic wells, cultured for 2 days in fetal bovine serum-Dulbecco's modified Eagle's medium to reach about 80% to 90% confluence, 2 x 10(4) cells/well and passed in Dulbecco's modified Eagle's medium free of fetal bovine serum before experimentation. A quantity of 3 microg of (125)I-AGT was added to each well at zero time.


RESULTS
The cells rapidly bound (125)I-AGT in a time dependent manner with saturation being achieved in 2 to 4 h. This binding was competitively inhibited by unlabeled AGT. Prior addition of a 100-fold excess of unlabeled AGT resulted in a 54% decrease in maximal binding. Bound AGT was also competitively displaced by AGT. Addition of a 200-fold excess of unlabeled AGT displaced 70% of the bound (125)I-AGT. Thus, approximately 30% of the total binding can be attributed to nonspecific binding. An acid wash (0.2 mol/L acetic acid, 0.5 mol/L NaCl, pH 2.5) at 4 degrees C removed 46% of the bound (125)I-AGT. An acid wash is known to dissociate cell surface ligand-receptor complexes, but does not remove internalized ligand.


CONCLUSIONS
The results of this study provide evidence for the existence of an AGT receptor on placenta-derived cells. This is the first report of an AGT receptor.
Tewksbury
Duane A
DA
Marshfield Medical Research and Education Foundation, Marshfield, Wisconsin 54449, USA. tewksbud@tznet.com
Pan
Nan
N
Kaiser
Steven J
SJ
D000808:Angiotensinogen / Q000378:metabolism* / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D006801:Humans; D007457:Iodine Radioisotopes; D010920:Placenta / Q000166:cytology / Q000378:metabolism*; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012084:Renin-Angiotensin System / Q000502:physiology*
D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D000808:Angiotensinogen