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Inhibition of sulfate transport in ehrlich ascites tumor cells by 4‐acetamido‐4′‐isothiocyano‐stilbene‐2,2′‐disulfonic acid (SITS)
Author(s) -
Villereal Mitchel L.,
Levinson Charles
Publication year - 1976
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040890213
Subject(s) - chemistry , sulfate , kinetics , reagent , chloride , membrane , biophysics , membrane transport , biochemistry , phosphate , inorganic chemistry , organic chemistry , biology , physics , quantum mechanics
The effects of the nonpenetrating amino reactive reagent 4‐acetamido‐4′‐isothiocyano‐stilbene‐2‐2′‐dilsulfonic acid (SITS) on anion transport (sulfate, chloride, and inorganic phosphate) were investigated in Ehrlich ascites tumor cells. Short time exposure to SITS produces a reversible inhibition (92%) of sulfate transport. The kinetics of interaction suggest that reversibly bound SITS competitively inhibits sulfate transport, Ki = 3 × 10 −6 M. Incubation of tumor cells with SITS (1 × 10 −4 M) for longer periods of time results in a time dependent irreversible inhibition of sulfate transport which obeys first order kinetics. The rate coefficient for the inactivation process is 0.040 min −1 . The kinetics of irreversible inhibition is best explained by the irreversible binding of SITS to the sulfate transport site, and therefore makes SITS a potentially useful probe for the quantitation of these sites in the tumor cell. The lack of effect of irreversibly bound SITS on either chloride or inorganic phosphate transport points to a specificity in the interaction of SITS with the tumor cell membrane, as well as indicating that an alternate pathway exists for the movement of these anions across the membrane.