PEPTIDEYY AND INSULIN COEXIST IN BETA-GRANULES IN B-CELLS OF THE MADAGASCAN LIZARD, ZONOSAURUS-LATICAUDATUS

PYY, a 36-amino-acid peptide belonging to the PP family, is often colo calized with glucagon in A cells in the gastroenteropancreatic system of vertebrates. However, both immunocytochemical and immunohistochemic al methods reveal this peptide in insulin-containing beta-granules in the lizard Zonosaurus laticaudatus. Absorption tests of PYY antiserum with insulin did not abolish the immunostaining of beta-granules with PYY antiserum, ruling out a cross-reaction between the PYY antiserum a nd insulin. This feature may be a reflection of the persistence of an ontogenetic character or a result of an adaptative mechanism that sele ctively activates the PP family of genes in the cellular line of B rat her than of A cells. (C) 1996 Academic Press, Inc.