Functional angiotensin II receptors on macrophages from isolated liver granulomas of murine Schistosoma mansoni.

Isolated liver granulomas from mice infected with Schistosoma mansoni contain components of the renin-angiotensin system. Angiotensin II is a major biologically active component of this system. It was therefore determined whether inflammatory cells within the granuloma possessed receptors for this hormone. Specific binding of angiotensin II to isolated granuloma macrophages was demonstrated by both fluorescence and radioligand assays. The binding of 125I-angiotensin II was saturable, dependent on radioligand concentration, and reversible. Scatchard analysis of binding data suggested a Kd of 0.25 nM with 526 binding sites per cell. The natural analogs of angiotensin II, angiotensin I and III, only weakly competed for angiotensin II binding sites. Exposure of macrophages to appropriate binding concentrations of angiotensin II resulted in a rapid dose-dependent increase in intracellular cAMP. It is therefore concluded that granuloma macrophages possess functional receptors for angiotensin II.