Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Recently, several studies have suggested that intracellular second messenger systems, such as activation of phospholipase C (PLC), which generates inositol 1,4,5-triphosphate (IP₃) and diacyglycerol (DAG), are involved in cerebral arterial contraction.⁷⁾⁸⁾ We have previously reported that hemolysate-induced Ca²⁺ mobilization may be mediated through G protein-coupled P_2u purinoceptors that activate phospholipase C.¹³⁾ Protein tyrosine kinases have been suggested as another signal transduction mechanism to play an important role in the regulation of vascular smooth muscle tone.¹⁴⁾¹⁵⁾ Receptor activation by agonists such as 5-HT, norepinephrine, angiotensin II, vasopressin and endothelin, not only activate PLC to generate IP₃ and DAG, which activates protein kinase C (PKC), but also phosphorylates intermediate protein tyrosine kinases which regulate intracellular Ca²⁺ and smooth muscle contractility.¹⁴⁾¹⁵⁾ We have shown previously that protein tyrosine kinase phosphorylation is triggered by hemolysate in cultured bovine endothelial cells as a cell signal to promote Ca²⁺ entry.¹⁶⁾

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