Differences in response between SHRSP and WKY vascular smooth muscle cells to inhibition of cell proliferation by sodium nitroprusside. 
The effects of sodium nitroprusside on the proliferation of cultured vascular smooth muscle cells (SMC) from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) were examined.  Sodium-nitroprusside (SNP, 1mM) inhibited DNA synthesis by SMC from SHRSP and WKY by 90% and 95%, respectively.  SNP also decreased cell proliferation.  However, SNP was inactive when SMC were pretreated 6 and 12 hrs before growth stimulation by FCS.  On the other hand, the inhibitory action of SNP decreased with time (posttreatment) in SHRSP SMC (42% inhibition at 12 hr post addition).  However, in WKY SMC, the decrease of inhibitory action was very slight and SNP still inhibited 73% of DNA synthesis at 12 hr post treatment.  SNP inhibited RNA synthesis for 3-6 hr and 6-9 hr after FCS stimulation, however no difference was noted between SHRSP and WKY.  Protein synthesis was inhibited more strongly by SNP (9-12 hr after FCS stimulation) in WKY SMC than SHRSP SMC.  It is probable that the specific protein(S) whose synthesis is inhibited by SNP is/are responsible for the differences in cell proliferation rate between SHRSP and WKY SMC.