Inhibition of sulfate transport in ehrlich ascites tumor cells by 4-acetamido-4′-isothiocyano-stilbene-2,2′-disulfonic acid (SITS)

✍ Scribed by Mitchel L. Villereal; Charles Levinson

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 667 KB
• Volume: 89
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040890213

✦ Synopsis

Abstract

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.