The AR42J acinar cell line was characterized as a potential cellular m
odel to assess the functional aspects of an exocrine pancreatic angiot
ensin system. Binding studies revealed that the AR42J cells express hi
gh affinity angiotensin II binding sites (K-d = 0.73 +/- 0.06 nM; B-ma
x = 292 +/- 15 fmol/mg protein, n = 3). Competition studies establishe
d that these cells, similar to the intact pancreas, express predominan
tly the AT(2) receptor subtype. The AT(2)-selective antagonists CGP 42
112A, PD 123177, and PD 123319 competed for the majority of angiotensi
n II binding. However, 10-15% of the angiotensin II binding sites were
competed for by the AT(1)-selective antagonist DuP 753 (Losartan). Af
finity labeling of these binding sites with [I-125]angiotensin II foll
owed by SDS gel electrophoresis under reducing conditions revealed a s
ingle band comprising a molecular mass of 108,000 Da. Competition with
unlabeled angiotensin II or the AT(2) antagonist, but not the AT(1) a
ntagonist, abolished the 108,000-Da band. In intact cells, angiotensin
II caused a rapid increase in intracellular calcium (Ca2+) using Fura
-2 as a Ca2+ indicator. Pretreatment of the cells with the AT(1) antag
onist DuP 753 completely inhibited the angiotensin II-induced rise in
Ca2+; however, the AT(2) antagonists CGP 42112A and PD 123177 were ine
ffective in blocking the Ca2+ increase. These results demonstrate that
this pancreatic acinar cell line expresses both AT(2) and AT(1) angio
tensin II receptor subtypes. The AT(1) receptor is coupled to the mobi
lization of Ca2+-a characteristic shared by AT(?)1 receptors in other
tissues.