THE ROLE OF CHONDROITIN SULFATE CHAINS OF URINARY TRYPSIN-INHIBITOR IN INHIBITION OF LPS-INDUCED INCREASE OF CYTOSOLIC-FREE CA2+ IN HL60 CELLS AND HUVEC CELLS

Preincubation of HL60 cells and HUVEC cells with urinary trypsin inhib itor (UTI) inhibited increase of cytosolic free Ca2+ induced by LPS. I n contrast, an increase of cytosolic free Ca2+ induced by LPS was not inhibited by deglycosylated UTI, UTI treated with monoclonal antibody of chondroitin sulfate, Ca-45(2+) binding showed that UTI binds Ca-45( 2+) dose-dependently, Scatchard plot analysis showed that UTI has two binding sites for Ca2+, a high affinity binding site (Kd=15 mu M) and a low affinity site (Rd=150 mu M), and that UTI has more than 70 Ca2binding sites per molecule, The Ca2+ binding capacity of deglycosylate d UTI and UTI treated with monoclonal antibody of chondroitin sulfate was markedly depressed, Furthermore, UTI forms multi-polymers in the p resence of Ca2+ as demonstrated by gel filtration and agarose gel elec trophoresis, These results suggest that UTI is a physiological Ca2+ ch elator on the cells and that the action is due to chondroitin sulfate chains of UTI. (C) 1997 Academic Press.