Summary
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1.
The serotonin (5-HT)-releasing action of active components partially purified from Toh's alkali kidney extract was studied by incubation with rabbit blood platelets.
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2.
The 5-HT release caused by the active components was shown to be practically un-affected by the pH (6.5–8.0) of the incubation media and was independent of the presence of Ca2+. The 5-HT release was negligible at lower temperatures (less than 30° C), an obvious release being observed only at 37° C. In the presence of glucose in the incubation medium, 5-HT liberation was depressed even with a glucose concentration as low as 1 μM. There was a stoichiometric relation between the platelet count and the dose of the extract; as long as the ratio of these two terms was fixed, the extent of 5-HT release could be kept nearly constant. The inhibitory effect of glucose was competitive.
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The active components seemed to suppress the amine influx into platelets incubated at 37° C, with14C-5-HT for 60 min but scarcely affected the influx at 20° C or 0° C. Glucose antogonised this inhibitory action of the extract. The findings suggest that the passive 5-HT exchange was not altered by the extract, but active amine uptake was affected.
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The author is grateful to Prof. A. Inouye and to Dr. K. Kataoka for their constant encouragement and kind help in preparing the manuscript. The present study was partly aided by a grant from the Ministry of Education of Japan.
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Shio, H. Mode of action on the platelet 5-HT of the active principles in Toh's alkaline tissue extract. Naunyn-Schmiedebergs Arch. Pharmak. 267, 123–134 (1970). https://doi.org/10.1007/BF00999395
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DOI: https://doi.org/10.1007/BF00999395