Immunohistochemical evidence for mast cells containing 5-hydroxytryptamine in rat portal vein.

Serotonin was localized to mast cells in the adventitia of the rat portal vein by indirect immunohistochemistry. The mastocytes where preferentially localized to a region delimited by the pyloric and splenic veins. Since neither 48/80 nor reaginic antibody induced a significant change in the intrinsic spontaneous activity of the portal vein it would appear that the mast cells are not involved in a direct vasomotor function. It is suggested that amines released from the mastocytes could regulate blood flow in the vasa vasorum and/or have a role associated with the sensory functions displayed by this vein.