Ontogenetic expression of chromogranin A and its derived peptides, WE-14 and pancreastatin, in the rat neuroendocrine system.

The ontogenetic expression of chromogranin A (CgA) and its derived peptides, WE-14 and pancreastatin (PST), was studied in the rat neuroendocrine system employing immunohistochemical analysis of fetal and neonatal specimens from 12.5-day embryos (E12.5), to 42-day postnatal (P42) rats. CgA immunostaining was first detected in endocrine cells of the pancreas, stomach, intestine, adrenal gland and thyroid at E13.5, E14.5, E15.5, E15.5 and E18.5, respectively. PST-like immunoreactivity was detected in endocrine cells of the pancreas at E13.5, stomach, intestine at E15.5, adrenal gland at E17.5 and thyroid at E18.5. WE-14 immunoreactivity was first observed in the immature pancreas at E15.5, mucosal cells of the stomach at E15.5, scattered chromaffin cells in the immature adrenal gland and mucosal cells of the intestine at E17.5 and thyroid parafollicular cells at E18.5. These data confirm that the translation of the CgA gene is regulated differentially in various neuroendocrine tissues and, moreover, suggests that the post-translational processing of the molecule is developmentally controlled.