Evidence for the coexistence and co-release of [Met]enkephalin and noradrenaline from sympathetic nerves of the bovine vas deferens.
The localization and neurosecretion of methionine-enkephalin was studied in sympathetic nerves of the bovine vas deferens. Immunostaining showed methionine-enkephalin-like immunoreactivity in a network of varicose nerve fibres in the smooth muscle layers of the vas deferens. When vas deferens homogenates were subjected to differential and sucrose density gradient centrifugation, methionine-enkephalin was found to parallel the distribution of noradrenaline in the more dense region of the gradient, where "heavy" or large dense-cored vesicles are present. Electron microscopic immunochemistry confirmed this finding and showed methionine-enkephalin-like immunoreactivity in large dense-cored vesicles. The release of methionine-enkephalin upon electrical stimulation was studied in superfusion experiments. The methionine-enkephalin secretion was shown to be Ca2+-dependent and was inhibited by adding the adrenergic neuron blocking drug guanethidine to the superfusion medium. We conclude that in the bovine vas deferens methionine-enkephalin is only present in large dense-cored vesicles of adrenergic neurons and that the peptide is released from these vesicles together with noradrenaline by a Ca2+-dependent mechanism.
De Potter
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De Potter
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D000320:Adrenergic Fibers / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D002851:Chromatography, High Pressure Liquid; D004744:Enkephalin, Methionine / Q000378:metabolism*; D006651:Histocytochemistry; D007158:Immunologic Techniques; D008297:Male; D008854:Microscopy, Electron; D009638:Norepinephrine / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013572:Synaptic Vesicles / Q000032:analysis; D014649:Vas Deferens / Q000294:innervation* / Q000502:physiology / Q000648:ultrastructure
D004744:Enkephalin, Methionine; D009638:Norepinephrine