The endocrine pancreas of glucagon-and somatostatin-immunized rabbits. I. Light microscopy and immunohistochemistry.

Peptide antibodies raised in rabbits are widely used in biology and medicine. During immunization of the animals, the respective antibodies may affect the endocrine cells physiologically responsible for the synthesis of peptides used as antigens. Since corresponding morphological data are still sparse, the rabbit endocrine pancreas was systematically investigated by light microscopy and immunocytochemistry after long-term immunization against glucagon and somatostatin. Both immunizations led to an increase in the number of islets (nesidioblastosis), to the development of giant islets (macronesia), and to changes in the relative proportions of the major types of endocrine cells or their hormonal content. The latter changes differed after either immunization: glucagon immunization resulted in hypertrophy and hyperplasia of glucagon cells and a decrease in their hormonal content; somatostatin immunization led to an increased proportion of somatostatin cells and a lowered hormonal content of insulin cells. The various alterations were expressed differently according to islet type; islets of the rabbit pancreas differ in size or angioarchitecture, and in the proportion and distribution of endocrine cells. The present findings point to autocrine or paracrine effects of the respective peptides. These effects, however, are obviously of differing significance in morphologically heterogeneous islets.