Peanut lectin binding sites in human foetal and neonatal pancreas

The histochemical binding sites of peanut agglutinin (PNA) to normal foetal and neonatal pancreas and to pancreatic tissue from two cases with persistent neonatal hyperinsulinaemic hypoglycaemia were studied. For the demonstration of masked PNA binding sites, neuraminidase digestion was utilized. In addition, pancreatic endocrine cells were identified by immunocytochemistry for insulin, glucagon and somatostatin. Likewise, double immunohistochemical staining for simultaneous visualization of PNA binding sites and insulin reactive cells was employed. In pancreatic exocrine tissue, PNA binding occurred in all cases without neuraminidase treatment. Insular endocrine cells expressed PNA binding both in normal neonatal cases and in those with hyperinsulinaemic hypoglycaemia, but only after neuraminidase treatment. In foetal pancreas, no PNA binding was found on endocrine cells even after neuraminidase treatment, and it was also absent from B-cells in areas of the normal neonatal pancreas that showed the characteristic picture of nesidioblastosis. The possible mechanisms involved in determining the different pattern of PNA reactivity in foetal and neonatal endocrine pancreas are considered.