Caveolin-1 is a protein component (of relative molecular mass 22,000) of th
e striated coat that decorates the cytoplasmic surface of caveolae membrane
s. Previous biochemical and molecular tests have indicated that caveolin-1
is an integral membrane protein that is cc-translationally inserted into en
doplasmic-reticulum membranes of fibroblast and epithelial cells such that
its carboxy- and amino-terminal ends are in the cytoplasm. Here we identify
caveolin-1 in the secretory pathway of exocrine cells. Secretion of caveol
in-1 from pancreatic acinar cells and a transfected exocrine cell line, but
not from Chinese hamster ovary cells, is stimulated by the secretagogues s
ecretin, cholecystokinin and dexamethasone. The secreted caveolin-1 co-frac
tionates with apolipoproteins, indicating that it may be secreted in a comp
lex with lipids.