MICROVASCULAR RESEARCH 35, 363-367 (1988) BRIEF COMMUNICATIONS Presence of Phenolsulfotransferase Activity in Microvascular Endothelial Cells: Formation of 5-HT-O-Sulfate in Intact Cells AUDREY ROBINSON-WHITE, **I JONATHAN L. COSTA,? JEAN-MARIE LAUNAY,$ AND DENISE D. FAY~ *Laboratory of Chemical Pharmacology, NHLBI, NIH, Bethesda, Maryland 20892, fClinica1 Neuropharmacology Branch, NIMH, NIH, Bethesda, Maryland 20892, SHGpital ST-Louis, 2 place de Dr. Fournier, 7S475 Paris, Cedex 10, France INTRODUCTION The development of techniques for isolating relatively pure, metabolically viable microvascular endothelial (MVE) cells, (Robinson-White and Beaven, 1982) has allowed us to investigate biochemical mechanisms within these cells. Endothelial cells accumulate 5hydroxytryptamine (5HT) by an active transport process of high affinity, and thus may regulate circulating 5-HT levels (Robinson- White e? al., 1981; Junod, 1972; Shepro and D’Amore, 1980). The disposition of S-HT inside endothelial cells, however, remains unclear. Although 5-HT is degraded by monoamine oxidase (MAO) (Junod, 1972), most (80-90%) of the 5-HT taken up by MVE cells remains unchanged (Robinson-White er al., un- published data). Nevertheless, no membrane bound storage sites for 5-HT have been described in MVE cells, and the action of other 5-HT metabolizing enzymes, such as phenolsulfotransferase (PST) (EC 2.8.2.1), on this 5-HT pool has not been previously investigated. PST is found in a variety of tissues in at least two forms, designated the M- and P-type (Rein et al., 1982). The M-type O-sulfates neurotransmitters, whereas the P-type acts predominately on phenolic compounds. The synthetic 5-HT de- rivative, difluoro-5-HT (diF-SHT) is a substrate for both types of enzyme activity (Costa et al., 1983). In human platelets, M-type PST is involved in the formation and maintenance of extravesicular amine stores. Pentachlorophenol is an effective inhibitor of P-type PST in some systems (Rein et al., 1982). We report that PST activity exists in MVE cells from rat and guinea pig, and that MVE cells may have the ability to O-sulfate 5-HT. ’ Audrey Robinson-White is the recepient of a National Research Service Award and is a Pharmacology Research Associate of the National Institute of General Medical Sciences. To whom reprints requests should be addressed at current address: Department of Anesthesiology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814. 363 0026-2862188 $3.00 Coovrieht Q 1988 bv Academic Press. Inc. All righi; oflreproduction in any form reserved. Printed in U.S.A.