Opioid and opioid-like receptors are activated by a variety of endogenous peptides including [Met]enkephalin (met), [Leu]enkephalin (leu), β-endorphin (β-end), α-neodynorphin, dynorphin A (dynA), B (dynB), big (Big dyn), nociceptin/orphanin FQ (N/OFQ); endomorphin-1 endomorphin-2 also potential peptides. The Greek letter nomenclature for the opioid receptors, μ, δ κ, is well established, NC-IUP...

The effect of the opioid receptor agonist methionine enkephalin (Met-enkephalin) and the opioid receptor antagonist naloxone on colonic carcinogenesis induced by azoxymethane was investigated in Wistar rats. Rats received ten weekly injections of 7.4 mg/kg of body weight of azoxymethane and injections of Met-enkephalin (50 micrograms/kg of body weight), naloxone (2 mg/kg of body weight), or Met...

Rats given high doses of colchicine (300-400 ug, i.c.v.) were used to investigate the comparative distribution of Leu-enkephalin and bovine adrenal medullary enkephalinprecursor fragment (BAM-22P) in the brain. Leu-enkephalin immunoreactive neurons have a widespread distribution throughout the neuraxis. In most areas adjacent section analysis showed BAM-22P and Leu-enkephalin immunoreactive per...

Selective immunocytochemical procedures, applied at the light and electron microscopical level, have resulted in the identification of three types of enkephalin-immunoreactive nerves in the feline gastrointestinal tract, including neurons containing either Met- or Leu-enkephalin immunoreactivity or those simultaneously storing both Met- and Leu-enkephalin immunoreactants. The three different ty...

Two enkephalin-containing polypeptides of 3600 and 4900 daltons have been isolated from extracts of bovine adrenal medulla, purified to homogeneity, and analyzed by a combination of automated Edman degradation and enzymatic time course hydrolysis. The 4900-dalton polypeptide contains two copies of enkephalin, one an internal [Met]enkephalin sequence, the other a [Leu]enkephalin sequence at the ...

Adrenal medullary chromaffin cells maintained in a chemically defined, serum-free medium retain high levels of both catecholamines and opiate-like peptides. At least 25% of the opioid activity as measured by radioreceptor assay is present as [Met]- and [Leu]enkephalin. Incubation of chromaffin cells with [3H]tyrosine and [35S]methionine for 3 days results in incorporation of 3H and 35S into [Me...

Exposure of bovine chromaffin cells in primary culture to 5 microM reserpine or 25 microM forskolin results in an increase in enkephalin peptide levels within 24-48 hr; 25 microM forskolin (or cholera toxin at 50 micrograms/ml) causes a 1.5- to 2-fold increase in enkephalin peptide levels, which is maximal after 48 hr of exposure and is totally blocked by addition of cycloheximide (0.5 microgra...

Adrenal chromaffin granules contain at least 10 peptides, ranging in size from 3 to 5 kilodaltons, that yield, upon digestion with trypsin, peptides that show specific binding to opiate receptors. All are distinctly different from beta-endorphin. Two of these peptides have been purified to homogeneity and subjected to chemical analysis. One is apparently a [Met]enkephalin precursor containing t...

Endogenous opioids participate in growth regulation. Liver regeneration relates to growth. Thus, we explored the expression of methionine enkephalin and of the delta opioid receptor 1 immunoreactivities with a polyclonal rabbit antibody in deparaffinized liver of patients with chronic liver disease. Fifteen of a total of fifty-eight samples expressed both opioid receptor and methionine enkephal...

Specific binding properties of the tritium-labeled delta opiate receptor agonist [3H][2-D-penicillamine, 5-D-penicillamine]enkephalin [( 3H][D-Pen2, D-Pen5]enkephalin) were characterized in the rat brain and in a mouse neuroblastoma-rat glioma hybrid cell line (NG 108-15). Saturation isotherms of [3H][D-Pen2, D-Pen5]enkephalin binding to rat brain and NG 108-15 membranes gave apparent Kd values...