Cytosolic retinoic acid binding protein in the human pancreas.

Cytosolic retinoic acid receptor in carcinoma, chronic pancreatitis, and normal pancreatic tissue were examined using sucrose density gradient centrifugation, isoelectric focussing on agarose gel and saturation analysis. Thirteen patients were studied. Cytosolic retinoic acid binding protein (cRABP) was detected in all the samples with chronic pancreatitis and pancreatic carcinoma, but not in the normal tissue. Using sucrose gradient centrifugation, the highest concentrations of cRABP were found in pancreatic carcinoma tissues, ranging from 5.5-23.9 pmol/mg protein. These concentrations were markedly different than in chronic pancreatitis tissue (0.7-2.7 pmol/mg protein). Saturation analysis of cRABP showed a mean dissociation constant of 21.5 nM and maximum binding sites of 5.2 pmol/mg protein. Cytosolic retinoic acid binding protein was separated at an isoelectric point of 4.5 on agarose gel. The presence of cRABP suggest that retinoic acid may have a role to play in the function of the pancreas.