The effect of 5‐hydroxytryptamine on the potassium exchange of human platelets

Abstract

The concentration of potassium in platelets freshly isolated from nine persons was 74 [plus or minus] 4.8 [mu]mole/1 OH platelets (mean [plus or minus] S.E.M.). The influx of potassium into platelets from citrated plasma at 37[degree]C, estimated with the use of 42r, was 18.3 [plus or minus] 1.6 n-mole/sec. lO*1 platelets. When plasma contained 5-hydroxytryptamine (5-HT) at a concentration of about 5 /[mu]g/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 /[mu]g/ml.) or much higher (50 [mu]g/ml.). The concentration of 5-HT in the platelets did not affect their potassium flux.