Binding sites on human lymphocytes for prostaglandins were examined by incubating cells with [3H]prostaglandin (PG) A1, E1, E2, F1α, and F2α. Specific reversible binding for [3H]PGE1 and E2 was found with a Kd of ~2 × 10-9M and a B max of ~200 binding sites per cell, assuming uniform distribution. We detected no specific binding of [3H]PGA1, F1α, or F2α to lymphocytes. Also, the addition of 10- to 1000-fold greater amounts of unlabeled PGA, F1α, or F2α did not inhibit the binding of [3H]PGE. The time course of [3H]PGE binding appeared to be bimodal with one component complete within 5 min at 37 °C and another component of binding increasing over a 40-min incubation. We feel that the rapid component of binding may represent cell surface receptors for PGE while the slower component may represent a specific uptake mechanism for PGE into the cell. Glass adherent cells had fewer binding sites than nonadherent cells. Preincubation of the cells overnight resulted in a loss of binding sites.
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