PT  - JOURNAL ARTICLE
AU  - M. DA PRADA
AU  - R. A. O'BRIEN
AU  - J. P. TRANZER
AU  - A. PLETSCHER
TI  - THE EFFECT OF 5,6-DIHYDROXYTRYPTAMINE ON UPTAKE, STORAGE AND METABOLISM OF 5-HYDROXYTRYPTAMINE BY BLOOD PLATELETS
DP  - 1973 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 213--219
VI  - 186
IP  - 2
4099  - http://jpet.aspetjournals.org/content/186/2/213.short
4100  - http://jpet.aspetjournals.org/content/186/2/213.full
SO  - J Pharmacol Exp Ther1973 Aug 01; 186
AB  - Incubation of isolated blood platelets of rabbits or guinea pigs with 5,6-dihydroxytryptamine (5,6-DHT) caused a decrease of the 5-hydroxytryptamine (5-HT) content in whole platelets as well as in isolated 5-HT storage organelles. Histamine and adenosine 5'-triphosphate remained unchanged. On electron microscopy, the number and size of the dense osmiophilic cores of the 5-HT storage organelles was increased. These alterations were especially striking in platelets of guinea pigs which normally contain very few osmiophilic organelles. Intraperitoneal injection of 5,6-DHT to guinea pigs caused similar electron microscopic changes as those seen in the incubation experiments. No ultrastructural damage due to 5,6-DHT was detected in platelets of rabbits and guinea pigs. Paper chromatography of lysates of isolated 5-HT storage organelles from rabbit platelets incubated with 5,6-DHT revealed the presence of substantial amounts of this compound. The uptake of 14C-5-HT by isolated platelets from normal and reserpine-treated guinea pigs was competitively inhibited by 5,6-DHT. In homogenates of rabbit platelets 5,6-DHT also competitively inhibited the oxidative deamination of 14C-tyramine. It is concluded that in blood platelets 5,6-DHT acts at three different sites, i.e., the 5-HT storage organelles, the cytoplasmic membrane and the mitochondria. © 1973 by The Williams & Wilkins Co.