Co-release of enkephalins and precursors with catecholamines from the perfused cat adrenal gland in situ

• Published in: The Journal of physiology Vol. 353; no. 1; pp. 157 - 169
• Main Authors: Chaminade, M, Foutz, A S, Rossier, J
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01-08-1984; Blackwell
• Subjects: Acetylcholine - pharmacology; Adrenal Glands - drug effects; Adrenal Glands - metabolism; Adrenals. Interrenals; Adrenomedullary hormones. Regulation; Animals; Biological and medical sciences; Catecholamines - metabolism; Cats; Chromatography, Gel; Chromatography, High Pressure Liquid; Electric Stimulation; Enkephalin, Methionine - metabolism; Enkephalins - metabolism; Female; Fundamental and applied biological sciences. Psychology; Male; Perfusion; Potassium Chloride - pharmacology; Protein Precursors - metabolism; Splanchnic Nerves - physiology; Vertebrates: endocrinology; Fissipedia; Carnivora; Adrenal glands; Enkephalin; Aminoacid derivative hormone; Peptide hormone; Catecholamine; In vitro; Neuropeptide; Opioid peptide; Prohormone; Vertebrata; Mammalia; Cat; Release
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1984.sp015329

We have compared the nature of the enkephalin-like material derived from proenkephalin present in the intact cat adrenal gland
with the material co-released with catecholamines from the perfused adrenal in response to splanchnic nerve stimulation and
to perfusions with solutions containing acetylcholine (ACh) or high potassium chloride (KCl). In cat adrenals most of the
enkephalin-like material was in the form of large enkephalin-containing peptides. Free (met)enkephalin immunoreactivity represented
only 25% of the total (met)enkephalin immunoreactivity as determined by enzymatic digestion of large enkephalin-containing
fragments. Electrical stimulation (15 Hz) of the splanchnic nerve or perfusion of the gland with ACh (0.1 mM) or KCl (50 mM),
applied for 10 min, induced an immediate release of free (met)enkephalin immunoreactivity, (met)enkephalyl-arg-phe immunoreactivity,
and of large (met)enkephalin-containing peptides. The release by all three modes of stimulation followed a pattern that paralleled
the output of catecholamines. A rapid fatigue of all secretory processes developed during the stimulation periods, similar
to that observed for catecholamines. During splanchnic nerve stimulation, each nanomole of catecholamine output was accompanied
by the output of 0.4 pmol free (met)enkephalin immunoreactivity, of 1.1 pmol total (met)enkephalin immunoreactivity and of
0.1 pmol (met)enkephalyl-arg-phe immunoreactivity. Analysis of the perfusate by high-pressure liquid chromatography revealed
that (met)enkephalin, (met)enkephalyl-arg-phe and (met)enkephalyl-arg-gly-leu were released in molar ratios of 4 to 1 to 1
which is similar to the ratio found in the precursor, proenkephalin. The ratio of total (met)enkephalin immunoreactivity to
free (met)enkephalin immunoreactivity in the perfusate was the same (approximately 2.7) during two successive periods of splanchnic
nerve stimulation separated by 10 min. When release was evoked by increasing the K+ concentration to 50 mM-KCl, this ratio
was increased more than twofold compared with that obtained by electrical stimulation of the splanchnic nerve. Analysis of
the perfusate by gel filtration showed that, during splanchnic nerve stimulation, 47% of the total (met)enkephalin immunoreactivity
eluted in fractions containing fragments of low molecular weight. When KCl was used as stimulus only 12% of total (met)enkephalin
immunoreactivity eluted in these fractions. The results indicate that the nature of the released peptides depends on the type
of stimulus used to evoke release.