BOVINE POSTERIOR PITUITARY - PRESENCE OF P65 (SYNAPTOTAGMIN), PC1,PC2AND SECRETONEURIN IN LARGE DENSE CORE VESICLES

The subcellular distribution of p65 (synaptotagmin), of the endoprotea ses PC1 and PC2 and of secretoneurin was studied in bovine posterior p ituitary by differential and density gradient centrifugation. Ah these peptides were found to be present in the neurosecretory granules (lar ge dense core vesicles). p65 can therefore participate not only in exo cytosis from small synaptic vesicles but also from large dense core ve sicles. Secretoneurin is a peptide derived from secretogranin II. Proc essing of the propeptide apparently occurs during axonal transport of the large dense core vesicles and is complete in the posterior pituita ry. Thus, stimulation of the hypothalamic magnocellular neurons can le ad to the release of this newly characterized, functional neuropeptide .