Determination of plasma serotonins level in patients with pregnancy induced hypertension.
Serotonin (5-hydroxytryptamine, 5-HT) is an important central nervous system neurotransmitter and neuromodulator, and nearly all central nervous system neurons receive afferents from serotonergic neurons that have cell bodies in the raphe nuclei of the brain stem (1, 2).
Recent reports of new and important roles for serotonin in the periphery have served to increase interest in circulating serotonin (6).
In an attempt to determine the best estimate of true PPP serotonin concentrations in humans, we have carried out a systematic literature search of previous reports of PPP serotonin to characterize the available data.
Information extracted from identified publications included details of the method used to prepare PPP and to determine serotonin concentrations, and the values (mean, median, range) reported for free plasma or PPP serotonin along with associated SD or SE.
A total of 101 reports that included concentrations of PPP serotonin in healthy controls were found, and the data from these reports were included in the summary statistical analyses (12-112) (see Table 1).
A systematic literature search revealed 101 reports of PPP serotonin concentrations in healthy humans.
The preanalytical and analytical factors that potentially affected the reported concentrations of PPP serotonin included (a) the venipuncture procedure, including site, needle gauge, syringe, and anticoagulant; (b) the centrifugation process, including tube type, force, time, temperature, and specific plasma portion removed; (c) the recovery of serotonin during all phases of sample handling; (d) the sample preparation procedure including any prepurification; (e) the separation or chromatographic method; and f) the specificity and sensitivity of the detection method.
As expected given the relatively nonselective nature of the extraction procedures used, early spectrofluorometric methods gave the highest PPP serotonin values.
It should be noted that the assumption is true only if appropriate recovery studies have been performed; recovery studies are especially important when measuring serotonin because of its demonstrated lability with respect to oxidative and enzymatic degradation.
The potential for erroneously high values is substantially increased when PPP serotonin is assayed, owing to the difficulty of preparing PPP without causing release of platelet serotonin and without platelet contamination.
The group of 5 reports (60, 66, 67, 101, 109) with concentrations around 1 nmol/L appear to us to likely offer the best estimate of human PPP serotonin concentration.