Abstract
Tritium-labeled 5-hydroxytryptamine (3H-5-HT) is selectively taken up by elements of the myenteric plexus distinguishable from adrenergic axons. This uptake has been analyzed in vitro in a dissected preparation of longitudinal muscle and myenteric plexus. 3H-5-HT could be taken up by the preparations against a concentration gradient. A portion of that taken up resisted subsequent washout and, on radioautographic examination, was confined to the myenteric plexus. The rate of uptake into this compartment at 37°176} C was saturable. The Km was 7.4 ± 1.5 S.E. x 10-7 M, and the Vmax was 0.22 ± 0.03 nmol/ g/ min. Uptake was highly temperature dependent. The Q10 (27-37°C) was 3.6. Uptake was reduced by inhibitors of glycolysis, such as F-, iodoacetate, 2-deoxy-D-glucose or glucose deprivation, but not by inhibitors of aerobic metabolism such as 2,4-dinitrophenol, CN-or by oxygen deprivation. Uptake was also inhibited by ouabain and appeared Na+-dependent. Uptake of 5-HT was not reduced by norepinephrine, even at 10 times the 5-HT concentration. The uptake of 5-HT by the myenteric plexus, therefore, appears to be a Na+-dependent, carrier-mediated, energy-requiring process that involves transport adenosine triphosphatase and can distinguish between 5-HT and norepinephrine.
Footnotes
- Received April 5, 1971.
- Accepted June 18, 1971.
- © 1971 by The Williams & Wilkins Company
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