Cellular Mechanisms Underlying Arteriolar Myogenic Tone

The aim of the studies was to investigate the role of protein tyrosine phosphorylation in myogenic responsiveness of rat skeletal muscle arterioles. Skeletal muscle arterioles with myogenic tone dilated in response to the broad spectrum tyrosine kinase inhibitors genistein and tyrphostin A47 and constricted to the tyrosine phosphatase inhibitor pervanadate. Tyrosine kinase activity was found to alter vessel diameter and modulate barteriolar tone. However, the results indicate that acute arteriolar myogenic constriction does not itself require tyrosine phosphorylation. Tyrosine phosphorylation of p44/42 MAPK was found to be dissociated from the myogenic contractile response. Phosphotyrosine was found to be elevated with increasing intraluminal pressure and when the arterioles were rendered passive by superfusion with Ca2+ deplete Krebs bicarbonate buffer. This finding suggests that the increased phosphotyrosine may be related to increased wall tension caused by the increased intraluminal pressure. It appears that the elevated phosphotyrosine signal may be related to signalling pathways related to growth and proliferation of smooth muscle following a sustained rise in arteriole transmural pressure.