Serotonin is a vasoactive amine which has been suggested to be a media
tor in a wide number of vascular pathologies. Alterations in periphera
l serotonin have been related to a major risk in suffering vascular di
seases in the diabetic population. Intraperitoneal administration of s
treptozotocin (STZ) to rats lead to a symptomatology similar to the di
abetic syndrome type I in humans, making this model suitable for study
ing changes in peripheral 5-HT in diabetes mellitus type I. Changes in
the levels and metabolism of serotonin in several peripheral tissues,
gastrointestinal tract, liver, lung, kidney, plasma and platelets, is
discussed in STZ-diabetic rats. An emphasis is made on serotonin tran
sport mechanism in platelets. As a whole, in the diabetes mellitus typ
e I, the data point to an alteration in the uptake/release of 5-HT in
platelets as well as to changes in 5-HT release from intestine, while
no major changes are apparent in hepatic, renal and lung metabolism.