Conversion of neuropeptide K to neurokinin A and vesicular colocalization of neurokinin A and substance P in neurons of the guinea pig small intestine

• Published in: Journal of neurochemistry Vol. 48; no. 1; p. 141
• Main Authors: Deacon, C F, Agoston, D V, Nau, R, Conlon, J M
• Format: Journal Article
• Language: English
• Published: England 01-01-1987
• Subjects: Animals; Chromatography, Gel; Chromatography, High Pressure Liquid; Guinea Pigs; Intestine, Small - innervation; Male; Myenteric Plexus - metabolism; Neurokinin A; Neurons - metabolism; Neuropeptides - metabolism; Substance P - metabolism; Synaptic Vesicles - metabolism; Tachykinins; Tissue Distribution
• ISSN: 0022-3042
• DOI: 10.1111/j.1471-4159.1987.tb13138.x

The highest concentration of neurokinin A-like immunoreactivity and substance P-like immunoreactivity in the guinea pig small intestine was associated with the myenteric plexus-containing longitudinal muscle layer. Chromatographic analysis of extracts of this tissue demonstrated the presence of neurokinin A and neuropeptide K but the probable absence of neurokinin B. A fraction of synaptic vesicles of density 1.133 +/- 0.003 g/ml was prepared from the myenteric plexus-containing tissue by density gradient centrifugation in a zonal rotor and was enriched 29 +/- 12-fold in the concentration of neurokinin A-like immunoreactivity and 43 +/- 13-fold in the concentration of substance P-like immunoreactivity. This fraction was separated from the fraction of vasoactive intestinal peptide-containing vesicles (density, 1.154 +/- 0.009 g/ml). Chromatographic analysis of lysates of the vesicles indicated the presence of neurokinin A but not neuropeptide K. It is postulated that beta-pre-protachykinin is processed to substance P, neurokinin A, and neuropeptide K in the cell bodies of myenteric plexus neurons but that conversion of neuropeptide K to neurokinin A takes place during packaging into storage vesicles for axonal transport. The data are consistent with the proposal that neurokinin A and substance P are stored in the same synaptic vesicle, but the possibility of cosedimentation of different vesicles of very similar density cannot be excluded.