Leukotriene D4 binding and signal transduction in rat glomerular mesangial cells

We examined the characteristics of [³H]leukotriene D₄ (LTD₄) binding to mesangial cells in culture. Binding of stereoselective, specific, saturable, and rapidly reversible. Two binding sites are recognized with dissociation constants and binding site densities at equilibrium of 2.2 and 16.8 nM and 1.1 x 10⁴ and 3 x 10⁴ binding sites per cell. LTD₄, LTE₄ (5R,6S)LTD₄, LTB₄, and the LTD₄-receptor antagonist. SKF 104353, competitively inhibit radioligand binding in the following rank order of potency: LTD₄ > LTE₄= SKF 104353 > (5R,6S)LTD₄ > LTB₄. LTD₄ also induces time- and concentration-dependent phosphoinositide hydrolysis in mesangial cells. Formation of inositol 1,4,5-trisphosphate (IP₃) is maximal at 5 s, followed by a time-dependent increase in inositol monophosphate generation, and inhibited by 100-fold excess concentration of SKF 104353. Addition of LTD₄ to mesangial cells is associated with an increase in intracellular pH and dose-dependent stimulation of [³H]thymidine incorporation and mitogenesis. Thus rat mesangial cells possess specific binding sites for LTD₄, the activation of which stimulates IP₃ formation and induces cellular alkalinization and mitogenic responses. These studies provide insight into the cellular basis for LTD₄-mesangial cell interactions, which are of potential pathophysiological relevance during acute glomerular inflammatory injury.