Elevated levels of pancreatic polypeptide in obese-hyperglycemic mice.

The concentration and distribution of pancreatic polypeptide (PP) was studied in hyperglycemic obese (ob/ob) mice and homozygous (+/+) controls. By radioimmunoassay, the concentration of PP in the pancreas of ob/ob mice was greater both in the duodenal lobe (70.7%) and in the body and tail (66.3%) when compared to identical areas of control pancreases. Analysis of immunostained pancreatic tissue indicated that the number of PP cells per islet cross-section was significantly increased (58%) in the ob/ob tissue. The calculated total number of PP cells per average islet was elevated three times in the ob/ob islet. However, the proportion PP cell volume relative to the islet volume in ob/ob was one-half that of control islets. These results clearly demonstrate an elevation in both the number of PP cells per islet and the concentration of PP in the diabetic ob/ob murine pancreas.