Reduced expressions of inducible nitric oxide synthase and cyclooxygenase-2 in vascular smooth muscle cells of stroke-prone spontaneously hypertensive rats.

Inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 are expressed in vascular smooth muscle cells stimulated with interleukin-1beta (IL-1beta), resulting in the production of nitric oxide (NO) and prostaglandins (PGs) such as PGI2. The iNOS and COX-2 proteins and their mRNA expressions in cultured vascular smooth muscle cells isolated from 6-7 week-old stroke-prone spontaneously hypertensive rats (SHRSP) were compared with those in the cells isolated from age-matched normotensive Wistar Kyoto rats (WKY). The IL-1beta-induced NO production and iNOS expression in vascular smooth muscle cells of SHRSP were significantly lower than those in cells of WKY. Similarly, PGI2 production and COX-2 expression were significantly lower in vascular smooth muscle cells of SHRSP than WKY, whereas there was no difference in the COX-1 expression. There were no significant differences in iNOS and COX-2 mRNA expressions between the two strains, suggesting that these protein expression may be reduced at the post-transcriptional level in cells of SHRSP. These results further suggest that the reduction of iNOS and COX-2 expressions in vascular smooth muscle cells may have relevance to the pathophysiology in SHRSP.