title: Density distribution of guinea pig myenteric plexus nerve endings containing immunoreactive substance P.
abstract: The present study was performed to investigate how myenteric plexus nerve endings containing substance P are distributed in sucrose density gradients in relation to nerve endings capable of taking up 3H-acetylcholine or 14C-noradrenaline. The peak of substance P-immunoreactivity (ISP) was found at a density of 1.157 +/- 0.001 g X ml-1, that of 3H-radioactivity at 1.160 +/- 0.002 and that of 14C-radioactivity at 1.162 +/- 0.002 g X ml-1 (mean +/- SEM, N = 6); there was considerable overlap. In a second set of experiments, the resuspended P2-pellet was layered upon a discontinuous density gradient consisting of 0.6, 1.0, 1.2 and 1.4 M sucrose. Nine fractions were recovered. There was a 2.5-3.4-fold increase in the relative specific activity of ISP in the 1.2 M fraction (density = 1.154 g X ml-1) and the adjoining interfaces. Conventional electron microscopy showed that synaptosomal elements were present in the transmitter-enriched fractions. It is concluded that the substance P-containing nerve endings of the guinea pig myenteric plexus co-distribute (and may be co-purified with) nerve endings utilizing noradrenaline or acetylcholine on sucrose density gradients.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient / Q000379:methods; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008854:Microscopy, Electron; D009197:Myenteric Plexus / Q000378:metabolism / Q000648:ultrastructure*; D009638:Norepinephrine / Q000378:metabolism; D013373:Substance P / Q000032:analysis*; D013574:Synaptosomes / Q000378:metabolism / Q000648:ultrastructure*; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D014316:Tritium; D013373:Substance P; D000109:Acetylcholine; D009638:Norepinephrine