Loading…
Tetraethylammonium Facilitates the Stimulation-Evoked Loss of the Enkephalins from the Myenteric Plexus of Guinea-Pig Ileum
The effects of electrical field stimulation on the contents of[Met]enkephalin and [Leu]enkephalin were determined in myenteric plexus-longitudinal muscle preparations of the guinea-pig small intestine. Cycloheximide (0.1 mM) was present in all experiments to prevent de nouveau biosynthesis. The two...
Saved in:
Published in: | Proceedings of the Royal Society of London. Series B, Biological sciences Biological sciences, 1981-10, Vol.213 (1191), p.171-182 |
---|---|
Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | The effects of electrical field stimulation on the contents of[Met]enkephalin and [Leu]enkephalin were determined in myenteric plexus-longitudinal muscle preparations of the guinea-pig small intestine. Cycloheximide (0.1 mM) was present in all experiments to prevent de nouveau biosynthesis. The two enkephalins were separated by high-performance liquid chromatography and assayed on the mouse vas deferens. Stimulation with submaximal pulses (50 mA, 0.5 ms) at a frequency of 10 Hz caused maximal losses of about 35% of [Met]enkephalin and [Leu]enkephalin after 3 h (108000 pulses). The plot of log (enkephalin content) against number of pulses was steeper during the first 30 min than during the later periods. Tetraethylammonium bromide (TEA, 10 mM) increased the [Met]enkephalin and [Leu]enkephalin contents of the non-stimulated preparations by about 50%. When the preparations were stimulated in the presence of TEA at 50mA and 1 Hz, the plots of loss of enkephalins against number of pulses were linear until the maximum of about 50% was reached. Compared with stimulation in the absence of TEA, the rate constant was 8 times greater for [Leu]enkephalin and 20 times greater for [Met]enkephalin. The absolute losses per pulse were about 13 times greater for [Leu]enkephalin and 27 times greater for [Met]enkephalin than in the absence of TEA. In the presence of bacitracin and a mixture of dipeptides, the enzymatic degradation of the enkephalins was sufficiently suppressed to cause an overflow of 30–60% of the enkephalins lost from their stores into the perifusing Krebs solution. Until it is possible to determine the preformed precursors, which are present in large quantities, the kinetic relationship between these precursors and the enkephalins cannot be investigated. A similar dilemma exists for the relationship between ‘released’ enkephalins and the losses from their stores. |
---|---|
ISSN: | 0962-8452 0080-4649 0950-1193 1471-2954 2053-9193 |
DOI: | 10.1098/rspb.1981.0060 |