摘要Objecitve To explore whether phosphoinositide-specific phospholipase C (PLC) activation via G protein in vascular smooth muscle cells (VSMCs) is altered in spontaneously hypertensive rats (SHR).Methods The VSMCs derived from aortae of SHR and Wistar-Kyoto (WKY) rats were loaded for 48 hours with myo-［3H］ inositol. Inositol phosphate release was initiated by the addition of 10-5 mol/L norepinephrine in intact cells or by guanosine 5'-0-(3-thio-trisphosphate) (GTP gamma S) in permeabilized cells. In the meantime, growth arrested VSMCs were stimulated by 10% calf serum for 0, 30, 45, or 60 min, then gene expressions of Gq alpha subunit (G alpha q) were observed.Results There were no significant differences in inositol-1,4,5-triphosphate (IP3) level and expression of G alpha q mRNA between quiescent VSMCs from SHR and that from WKY. When stimulated by norepinephrine, IP3 production increased transiently with a peak level at 10 s in VSMCs from WKY, and a rapid biphasic IP3 response, which was significantly higher than that of WKY, in VSMCs from SHR had been observed. G proteins activated by GTP gamma S significantly raised IP3 production in VSMCs from SHR compared to WKY (SHR vs WKY: 234.8%±29.2% vs 142.4%±12.0% of basal IP3, P<0.05). In addition, the serum effect showed an significant increase in expression of G alpha q mRNA in VSMCs from SHR.Conclusions The hereditary factors are not the only variable regulating IP3 metabolism and G alpha q gene expression. Influences of multi-environmental factors such as vasoactive compounds, together with genetic predisposition, palys an important role in the highly sensitive response of IP3 production and G alpha q gene over-expression in SHR.