Separate ultrastructural distributions of neurophysin and C-terminal glycopeptide within dense core vesicles in rat neural lobe.

The distribution of the neurohypophysial prohormone products neurophysin and C-terminal glycopeptide within dense core vesicles were investigated at the ultrastructural level using quantitative immunogold labeling of rapidly frozen rat neural lobes. In vasopressin vesicles, gold particles after labeling for the glycopeptide were found significantly closer to membrane (chi = 16 nm) than were particles after labeling for neurophysin (chi = 32 nm). This distribution supports a previous histochemical localization of glycopeptide to the rim of vasopressin vesicles and suggests there is morphological segregation of prohormone products within the vesicle.