The platelet phenolsulfotransferase is not indispensable for the sulfoconjugation of plasma catecholamines.

To investigate the role of platelets, a proposed primary site of catecholamine sulfoconjugation, we determined plasma free and sulfoconjugated catecholamines and platelet phenolsulfotransferase activity in severe platelet defficiency states. We found that even in the presence of very low platelet counts, the plasma concentrations of sulfoconjugated catecholamines were within normal limits. Although the platelet phenolsulfotransferase activity expressed per number of platelets was normal there was a considerable decrease of the total platelet phenolsulfotransferase activity. This suggests that the platelet phenolsulfotransferase is not indispensable for the sulfoconjugation of catecholamines and this process can occur elsewhere. A preliminary finding of lower platelet phenolsulfotransferase activity in platelet deficiency states with reduced platelet generation (because of reduced megakaryocytes) than in those states with a decreased platelet survival, suggests that the phenolsulfotransferase is synthesised in the megakaryocytes and the platelets are only carriers of this enzyme.