CERTAIN pharmacological effects of serotonin might be related to its action on the permeability of cell membranes to various ions. It has been shown that serotonin inhibits the pigment effusion, sodium uptake and potassium efflux from slices of red beetroots in vitro1. The loss of potassium from erythrocytes in cold storage is reduced by serotonin2. An increase of the efflux of sodium and potassium from the isolated skin of a frog was also shown in the presence of serotonin3. This latter effect was not considered to be the result of non-specific damage of the cell membranes, because the permeability to Evans blue or sucrose was not affected by serotonin3. It is, however, well known that serotonin exerts a marked effect on the capillary permeability in rats4-6. Following a different approach, Woolley has proposed that there is an interaction between serotonin and calcium in isolated organs on the basis that serotonin no longer stimulates the uterus in the presence of a calcium-chelating agent7. This finding was interpreted as an effect of serotonin in facilitating the penetration of calcium into the cells8. On the other hand, calcium seems to be an important factor for serotonin release during the antigen-antibody reaction9,10.
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