Alteration of the Soluble Guanylate Cyclase System in the Vascular Wall of Lead-Induced Hypertension in Rats

Low-level lead exposure is a known cause of hyper- tension that has been associated with increased reactive oxygen species activity and endothelial-dependent vasorelaxation im- pairment. The effect of lead exposure on the vascular nitric oxide (NO)/cyclic guanocine monophosphate (cGMP) system was analyzed. Wistar rats were exposed to 5 ppm lead acetate in the drinking water during 30 d. Mean arterial BP increased significantly in the lead-treated rats. Relaxation to both acetyl- choline and sodium nitroprusside (SNP) was reduced in lead- treated rats; however, the vascular wall of lead-administered rats showed an increased expression of endothelial NO syn- thase. The expression of both subunits (1 and 1) of soluble guanylate cyclase (sGC) and the cGMP accumulated in the vascular wall were decreased in lead-treated rats. Cotreatment of lead with vitamin C (3 mmol/L) prevented the increase on mean arterial BP, improved the relaxation to both acetylcholine and sodium nitroprusside, and restored the normal expression of endothelial NO synthase and sGC proteins in the vascular wall. In conclusion, lead exposure altered both the endotheli- um-dependent and -independent relaxing response and induced a reduced expression of sGC in the vascular wall. These effects were abrogated with the antioxidant vitamin C, which suggests the involvement of reactive oxygen species in the regulation of the NO/cGMP relaxing system in the vascular wall of lead- treated rats.