Differential release of enkephalin and enkephalin-containing peptides from perfused cat adrenal glands.
We have compared the enkephalin-like material derived from proenkephalin released from perfused cat adrenal glands stimulated with pilocarpine (5 X 10(-4)M) and nicotine (5 X 10(-6) M). In addition, two doses of acetylcholine (10(-5) and 10(-4) M) and 50 mM K+ were tested. Free Met-enkephalin immunoreactivity and total Met-enkephalin immunoreactivity, as determined by enzymatic digestion of large enkephalin-containing fragments, were coreleased with catecholamines. Free Met-enkephalin immunoreactivity represented 13% of total immunoreactivity for nicotinic stimulation, 46% for pilocarpine, 33% for 10(-5) M acetylcholine, 22% for 10(-4) M acetylcholine, and 16% for 50 mM K+. Analysis of the perfusate by gel filtration showed that 80% of the total Met-enkephalin immunoreactivity whose release was induced by pilocarpine was eluted in fractions corresponding to fragments of low molecular weight, whereas these fractions accounted only for 10% of the total Met-enkephalin immunoreactivity whose release was induced by nicotine. HPLC analysis of low-molecular-weight peptide fractions revealed that Met-enkephalin, Met-enkephalin-Arg-Gly-Leu, and Met-enkephalin-Arg-Phe represented 69% of total Met-enkephalin immunoreactivity whose release was induced by pilocarpine. These results indicate that selective activation of muscarinic receptors is followed by release of low-molecular-weight material, whereas nicotine application also yielded high-molecular-weight peptides. Furthermore, increasing the acetylcholine concentration from 10(-5) to 10(-4) M and using 50 mM K+ increased proportionally the high-molecular-weight peptide secretion. Results are discussed in relation to the existence of a heterogeneous population of granules either in the same cell or in different cells, containing proenkephalin-derived peptides. (ABSTRACT TRUNCATED AT 250 WORDS)
Vindrola
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Sección Sustancias Vasoactivas, Instituto de Investigaciones Médicas, Buenos Aires, Argentina.
Ase
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Finkielman
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Nahmod
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D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002415:Cats; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004744:Enkephalin, Methionine / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D005260:Female; D008297:Male; D008970:Molecular Weight; D009538:Nicotine / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology
D004745:Enkephalins; D011976:Receptors, Muscarinic; D010862:Pilocarpine; D004744:Enkephalin, Methionine; D009538:Nicotine; D000109:Acetylcholine; D011188:Potassium