Raised levels of an endogenous nonadrenergic substance in the serum of pregnancy-induced hypertension patients.

A clonidine-displacing substance (CDS) was isolated from bovine brain and shown to mimic clonidine in peripheral tissues. CDS acts--contrary to clonidine--by increasing the mean arterial pressure in the CNS. Methanolic extract from sera of patients with pregnancy-induced hypertension (PIH) showed a significant increase in CDS levels as compared with sera of either normal or chronic hypertensive pregnancy. Although small amounts of CDS were found in the placenta, no positive correlation between placental levels of CDS and serum CDS levels was observed. The pharmacological properties of CDS and its higher levels in sera of PIH patients suggest that CDS is a sympathetic agent involved in the pathophysiology of PIH.