Uptake of 5-hydroxytryptamine in blood platelets and its inhibition by drugs: role of plasma membrane and granular storage

Abstract

The initial uptake of 3H‐5‐hydroxytryptamine (3H‐5‐HT) showed linearity for short time intervals in normal and reserpinized blood platelets of guinea‐pigs, but was lower in reserpinized platelets. The Km values for the 3H‐5‐HT uptake were virtually identical in normal and reserpinized platelets, whereas Vmax was lower in the latter. Imipramine and chlorpromazine caused the same percentage inhibition of 3H‐5‐HT uptake in normal and reserpinized platelets; the reserpine‐like compound Ro 4–1284 inhibited the uptake of 3H‐5‐HT in the normal, but not markedly in the reserpinized platelets. Haloperidol, prenylamine and Ro 4–9040 were more potent inhibitors in normal than in reserpinized platelets. It is concluded that (a) the Km of the initial uptake of 5‐HT by platelets is probably determined by the mechanism at the plasma membrane, whereas Vmax may be codetermined by the intracellular storage capacity, (b) platelets are models for differentiating the site of action (plasma membrane or storage organelles) of drugs interfering with 5‐HT uptake, and (c) neuroleptics‐ and reserpine‐like compounds may either act selectively on the plasma membrane or on the intracellular storage organelles, or affect both of these subcellular sites.

Tryptophan-induced lowering of blood pressure and changes of serotonin uptake by platelets in patients with essential hypertension

“…3). As the K M of the initial uptake of 5-HT by platelets is probably determined by mechanisms at the plasma membrane [12], it may be suggested that alterations at the membrane could be responsible for the different uptake kinetics in patients with high blood pressure.…”

Serotonin uptake, storage, and synthesis in an immortalized committed cell line derived from mouse teratocarcinoma.

“…(i) The high 5-HT concentration of the culture medium (0.1-1 AM) might downregulate both the rate of 5-HT uptake and the activity of tryptophan hydroxylase. Such an explanation has been put forward for platelets (50) and MTC cells (24). (ii) Based upon the homogeneity of the induced cell population, each 1C11* cell may contain a low number of functional carrier molecules compared to adult serotoninergic cells.…”

Liberation of Catecholamines From Blood Platelets

“…In platelets incubated with imipramine (10-7 M), which completely blocks the uptake of 5-HT (Laubscher & Pletscher, 1979a) (Table 1).…”