Neonatal rat islets of Langerhans and fetal rat pancreas. Isolation, immunohistochemical, functional, and autoradiographic evaluation.

The aim of this study was to develop an optimal isolation technique for neonatal rat islets of Langerhans, to perform functional evaluation in vitro, to evaluate immunohistochemically isolated rat islets and fetal rat pancreata after a variable period of culture, and to study growth potentials by means of autoradiography. The islets were isolated using minor modifications of standard procedures including collagenase and DNase. Islets were separated on a discontinuous Percoll gradient. The maximum yield of islets amounted to 240 per pancreas. Fetal pancreata from rats were cultured under similar conditions as neonatal islets to compare their insulin secretory capacity after different periods of culture. The insulin secretion increased gradually, and isolated islets achieved a similar secretion potential to adult rat islets. The mitotic activity of both islets and fetal pancreata was confirmed using tritiated thymidine. The isolation procedure was found suitable for producing well-functioning islets, which could be kept in culture for a period of about 1 month without deterioration in their insulin secretory capacity. The gradual increase in insulin secretory capacity of islets and fetal pancreata was due, in part, to hyperplasia and not just hypertrophia. Autoradiographical evaluation revealed a high mitotic activity after culture, in particular of fetal pancreata. Fetal pancreata cultured for about 10 days showed a phenomenon of budding endocrine cells at the organ surface. A high mitotic activity was found in these buds.