Antibodies From Preeclamptic Patients Stimulate Increased Intracellular Ca Mobilization Through Angiotensin Receptor Activation

signaling pathways. Sera of 30 pregnant patients, 16 diagnosed with severe preeclampsia and 14 normotensive, were examined for the presence of IgG capable of stimulating intracellular Ca mobilization. IgG from all preeclamptic patients activated AT1 receptors and increased intracellular free calcium. In contrast, none of the normotensive individuals had IgG capable of activating AT1 receptors. The specific mobilization of intracellular Ca 2 by AT1-AAs was blocked by losartan, an AT1 receptor antagonist, and by a 7-amino-acid peptide that corresponds to a portion of the second extracellular loop of the AT1 receptor. In addition, we have shown that AT1-AA–stimulated mobilization of intracellular Ca results in the activation of the transcription factor, nuclear factor of activated T cells. Conclusions—These results suggest that maternal antibodies capable of activating AT1 receptors are likely to account for increased intracellular free Ca concentrations and changes in gene expression associated with preeclampsia.