Effects of peripheral stem cell or bone marrow reinfusion on peripheral serotonin metabolism

Reinfusion of autologous hematopoietic peripheral blood stem cells (PBSC) or bone marrow is often accompanied by flushing, dyspnea, abdominal cramping, nausea and diarrhea. These symptoms and the observation that they can be prevented by ondansetron, a selective 5-HT3 receptor antagonist, led to the assumption that these side-effects are due to infusion of free serotonin during the reinfusion of PBSC or bone marrow. Twenty-five patients with solid tumors received, after myeloblative chemotherapy, a total of 30 reinfusions of PBSC and/or bone marrow. In 17 patients, serotonin levels in the bags containing the PBSC were measured. In all patients, platelet serotonin levels were determined before and 1 h post-reinfusion. In addition, before and 24 h after reinfusion urine was collected for determination of 5-hydroxyindole acetic acid (5-HIAA) and serotonin concentrations. Mean (+/- s.d.) total serotonin concentration in the bags was 2404 +/- 1555 nmol/l. Mean total volume reinfused was 471 +/- 185 ml. After reinfusion, the mean (+/- s.d.) levels of serotonin in platelets in patients increased from 3.2 +/- 1.4 nm/10(9) at baseline to 3.8 +/- 2.0 nm/10(9) (P = 0.02). Neither 24 h urinary 5-HIAA nor serotonin levels were affected. These results indicate that reinfusion of PBSC or bone marrow is accompanied by substantial infusion of free serotonin, which might explain the observed side-effects and justify the use of 5-HT3 receptor antagonists as pre- medication for this procedure.