1. The concentration of potassium in platelets freshly isolated from nine persons was 74 +/- 4.8 mumole/10(11) platelets (mean +/- S.E.M.).2. The influx of potassium into platelets from citrated plasma at 37 degrees C, estimated with the use of (42)K, was 18.3 +/- 1.6 n-mole/sec. 10(11) platelets.3. When plasma contained 5-hydroxytryptamine (5-HT) at a concentration of about 5 mug/ml., the influx of potassium into platelets was increased for as long as they took up 5-HT. This effect was absent when the concentration of 5-HT was either lower (2 mug/ml.) or much higher (50 mug/ml.).4. The concentration of 5-HT in the platelets did not affect their potassium flux.

Blood Platelets↗

PubMed1967

Histamine in the plasma and gastric juice of cats during infusions of [14C] histamine.

1. In anaesthetized cats with gastric fistulae, the relation was investigated between the rate of gastric secretion and the histamine contents of the plasma and the gastric juice during intravenous infusions of [(14)C]histamine for 3 hr.2. In the first hour only, some endogenous histamine appeared in the gastric juice.3. There was no quantitative relation between the histamine that was infused and that which appeared in the gastric juice.4. There was no correlation between the rate of gastric secretion and the concentration of histamine in either plasma or gastric juice.5. It was concluded that the secretion of histamine into the gastric juice was not essential to gastric secretion.

Animals↗

PubMed1967

The uptake of amines by human erythrocytes in vitro.

1. Human erythrocytes incubated at 37 degrees C in Krebs bicarbonate solution at pH 7.5 took up 5-hydroxytryptamine, histamine and (-)-noradrenaline at slow rates which were proportional to the concentration of the amines in the medium at least up to 16 mug/ml., in accordance with a simple diffusion process.2. The initial velocity of uptake was greatest for 5-hydroxytryptamine, about 4 times less for histamine and about 20 times less for (-)-noradrenaline; (+)-noradrenaline was not taken up.3. Comparison of uptake measurements by bio-assay and by radioactivity indicated that, after 1 hr, about 10% of each amine taken up had been inactivated.4. At 2 degrees C the uptake of all three amines was greatly diminished. The presence of the antagonists cocaine, chlorpromazine, lysergic acid diethylamide, mepyramine and pronethalol (at 10(-6) or 10(-5) g/ml.) did not affect uptake of the amines.5. In the steady state the ratios of concentration of the amines between cells and medium were greater than could be accounted for by a Donnan distribution.6. Cells which had taken up amines lost most but not all of them into amine-free medium, at rates which were slower than the corresponding rates of uptake. It was concluded that the amines are partially bound in the cells, noradrenaline most and histamine least.7. The slow diffusion of amines into, and the small amounts retained by, erythrocytes indicate that they do not contribute significantly to the rapid termination of the pharmacological actions of these amines in vivo.

Carbon Isotopes↗

PubMed1967