Subcellular Distribution of Opioid Peptides in Rat Hypothalamus and Pituitary |
| |
Authors: | C J Molineaux J G Rosenberger B M Cox |
| |
Institution: | Department of Pharmacology, Uniformed Service, University of the Health Sciences, Bethesda, Maryland, U.S.A. |
| |
Abstract: | Homogenates of rat anterior lobe (AL) and neurointermediate lobe (NIL) pituitary and rat hypothalamus were subjected to subcellular fractionation and density gradient centrifugation. The subcellular distribution of immunoreactive dynorophin A (ir-Dyn A) in NIL was found to be similar to that of ir-arginine vasopressin (ir-AVP). ir-Dyn A migrated as a discrete band on sucrose density gradients, which corresponded in sedimentation rate to that of ir-AVP, suggesting that these two peptides are stored within organelles of similar size and density. Two other products of prodynorphin, ir-alpha-neoendorphin (ir-alpha-nEND) and ir-Dyn A-(1-8) also comigrated with ir-AVP. ir-Leu5]-enkephalin (ir-LE), which may be a product of prodynorphin or proenkephalin, was also found to migrate in this region of the gradient. When a homogenate of rat hypothalamus was prepared using a method that has been developed for synaptosome isolation, ir-Dyn A was found to comigrate with Na+/K+-activated adenosine triphosphatase (Na/K-ATPase), a synaptosomal marker enzyme. Using a more concentrated homogenate ir-Dyn A was found to migrate to a less dense region where peptide-containing synaptic vesicles have previously been localized. When a synaptosomal preparation was lysed in hypotonic solution a shift was seen in the migration rate of ir-Dyn A to this region of the gradient (containing putative synaptic vesicles). Thus the bulk of hypothalamic dynorphin appears to be present within synaptosome-like structures which, upon lysis, release a less dense, smaller subcellular organelle corresponding in sedimentation characteristics to other types of peptide-containing synaptic vesicles.(ABSTRACT TRUNCATED AT 250 WORDS) |
| |
Keywords: | Dynorphin Leucine enkephalin [Met5]-enkephalin-Arg6-Phe7 Sucrose density gradients Synaptosomes Synaptic vesicles |
|
|