PAF and hematopoiesis. II. Elevated levels of plasma paf acetylhydrolase after rapid infusion of 5-fluorouracil in cancer patients.

Blood platelet-activating factor (PAF) levels are regulated by a plasma PAF acetylhydrolase. We investigated its levels in cancer patients during the course of a 5-day 5-fluorouracil (5-FU) treatment. PAF acetylhydrolase increased in nine patients with daily bolus infusion of 0.4 g 5-FU per m2 of body surface (81.7 +/- 8.7 nmol PAF/min/ml vs. 66.6 +/- 7.0; P < 0.001 for day 5 as compared to day 1). By contrast PAF acetylhydrolase did not change in seven patients with continuous infusion of 5-FU. The meaning of these results is discussed in respect of the immunoregulatory role of PAF.