Escherichia coli cells contain and secrete into the growth medium a heat-stable tryptic enzyme, which degrades the radiolabeled dynorphin tracer peptide during radioimmunoassay, simulating the presence of "immunoreactive dynorphin". The validity of an immunoassay procedure, in each new application, must remain in doubt until tracer integrity has been proved.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Reduction in opiate receptor reserve in morphine tolerant guinea pig ilea.

Spare opiate receptors in the guinea pig ileum have been detected by the use of the opiate receptor alkylating agent beta-chlornaltrexamine (CNA). Treatment of the guinea pig ileum longitudinal muscle in vitro with low concentrations (less than 10nM) of CNA resulted in an irreversible parallel shift to the right of the normorphine log concentration response curve. With increasing concentration of the reagent, the agonist EC50 becomes progressively greater. Finally a point is reached at which the maximal agonist effect decreases, so that parallelism is no longer seen. The maximal parallel shift provides a measure from which one can estimate the spare receptor fraction that is present in untreated tissue. In ilea from normal guinea pigs, roughly 80-90% of the opiate receptors for normorphine were found to be spare. Even after the largest parallel shifts that could be achieved, the naloxone Ke value for antagonism was unchanged, indicating that normorphine acts through spare mu receptors. Ilea from guinea pigs made tolerant by chronic morphine pellet implantation were found to be more sensitive to the effects of CNA treatment; there was a reduction in the number of spare receptors for normorphine. It is suggested that the opiate spare receptor fraction is physiologically modulated to control neuronal sensitivity to opioid effect.

Animals↗

PubMedDate not supplied

Two "big" dynorphins from porcine pituitary.

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Amino Acid Sequence↗

PubMedDate not supplied

Opioid peptide identity and localization in hippocampus.

The hippocampus contains three times as much dynorphin-17 immunoreactivity (ir) as enkephalin-ir. Hippocampal mossy fibers exhibit weak enkephalin and strong dynorphin immunostaining. Intrahippocampal colchicine injections, which selectively destroy dentate granule cells, reduce enkephalin-ir and dynorphin-ir in mossy fibers. Intraventricular kainic acid, which causes degeneration of CA3-4 pyramidal cells, results in increased enkephalin immunostaining in mossy fibers. The enkephalin-ir cells and fibers of the entorhinal cortex which innervate the hippocampus and dentate gyrus do not contain dynorphin-ir.

Animals↗

PubMedDate not supplied

Selectivity of dynorphin for kappa opioid receptors.

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Animals↗

PubMedDate not supplied

Dynorphin immunocytochemistry in the rat central nervous system.

The distribution of dynorphin in the central nervous system was investigated in rats pretreated with relatively high doses (300-400 micrograms) of colchicine administered intracerebroventricularly. To circumvent the problems of antibody cross-reactivity, antisera were generated against different portions as well as the full dynorphin molecule (i.e., residues 1-13, 7-17, or 1-17). For comparison, antisera to [Leu]enkephalin (residues 1-5) were also utilized. Dynorphin was found to be widely distributed throughout the neuraxis. Immunoreactive neuronal perikarya exist in hypothalamic magnocellular nuclei, periaqueductal gray, scattered reticular formation sites, and other brain stem nuclei, as well as in spinal cord. Additionally, dynorphin-positive fibers or terminals occur in the cerebral cortex, olfactory bulb, nucleus accumbens, caudate-putamen, globus pallidus, hypothalamus, substantia nigra, periaqueductal gray, many brain stem sites, and the spinal cord. In many areas studied, dynorphin and enkephalin appeared to form parallel but probably separate anatomical systems. The results suggest that dynorphin occurs in neuronal systems that are immunocytochemically distinct from those containing other opioid peptides.

Animals↗

PubMedDate not supplied

Opioid and other peptides as inhibitors of leumorphin (dynorphin B-29) converting activity.

A thiolprotease from rat brain membranes was shown to convert synthetic dynorphin B-29 (Dyn B-29, "leumorphin") to the tridecapeptide dynorphin B (Dyn B, "rimorphin"). This represents a "single-arginine cleavage" between threonine-13 and arginine-14 of the substrate. The dynorphin converting activity displayed typical Michaelis-Menten kinetics with an apparent Km for the substrate of 0.58 microM. Surprisingly, a synthetic peptide, Dyn B-29-(9-22), which contains the cleavage site, did not inhibit the activity. Dyn A inhibited the activity competitively with an apparent Ki of 3.7 microM. The converting activity was also inhibited by Dyn A-(6-17) but not by Dyn A-(8-17), suggesting a role of Arg6-Arg7 in the inhibition of converting activity. Bovine adrenal medulla Peptide E inhibited the converting activity substantially whereas metorphamide did not, suggesting the importance of COOH-terminal residues in recognition. Beta-Endorphin was an effective inhibitor of converting activity, and [alpha-N-acetyl]beta-endorphin was not, indicating a crucial role of the free NH2-terminus in recognition by the enzyme. ACTH inhibited the activity competitively with an apparent Ki of 39 nM. The converting activity was also inhibited substantially by ACTH-(1-13) but not by alpha-MSH, again indicating a requirement of the free NH2-terminus for recognition. The above results suggest that the converting enzyme recognizes peptides of the three known opioid gene families.

Adrenocorticotropic Hormone↗