Pressure-dependent contribution of Rho kinase-mediated calcium sensitization in serotonin-evoked vasoconstriction of rat cerebral arteries

Abstract

Our understanding of the cellular signalling mechanisms contributing to agonist-induced constriction is almost exclusively based on the study of conduit arteries. Resistance arteries/arterioles have received less attention as standard biochemical approaches lack the necessary sensitivity to permit quantification of phosphoprotein levels in these small vessels. Here, we have employed a novel, highly sensitive Western blotting method to assess:

Cytoskeletal Reorganization Evoked by Rho-associated kinase- and Protein Kinase C-catalyzed Phosphorylation of Cofilin and Heat Shock Protein 27, Respectively, Contributes to Myogenic Constriction of Rat Cerebral Arteries

“…An identical maximal level of LC 20 phosphorylation of ϳ50% was previously detected in RMCAs exposed to 1, 3, or 10 M 5-HT at 10 mm Hg (52). Based on these data, we quantified the changes in LC 20 , calponin, and caldesmon phosphoprotein and G-actin content caused by pressurization from 10 to 80 mm Hg in the presence of 5-HT (1 M), or in the reverse situation, during exposure to 5-HT (1 M) after stable development of myogenic tone at 80 mm Hg.…”

The Role of Actin Filament Dynamics in the Myogenic Response of Cerebral Resistance Arteries

“…Once again, no phosphorylation of CPI-17 was detected under any conditions. 9 These data imply that the cellular mechanism(s) used by extrinsic vasoconstrictor factors to evoke contraction are influenced by the presence of myogenic activation. In the example cited above, serotonin-evoked contraction was due exclusively to MLCK activation in the absence of intraluminal pressurization.…”

“…It is also of potentially great importance that PKCd and, less effectively, PKCa, have been shown to phosphorylate the same sites in HSP27 as MK2, 144 given that PKC has been implicated in the myogenic response. 8,9,14,54,73,74 Direct evidence of PKC-mediated actin polymerization during the myogenic response has come from measurements of G-actin content in rat gracilis arteries. The myogenic response was inhibited by pretreatment with the PKC inhibitor GF109203X, without an effect on CPI-17 phosphorylation, and increased intraluminal pressure decreased G-actin content in a GF109203X-dependent manner (Moreno-Dominguez et al, submitted).…”

“…5,6 The intrinsic development of myogenic tone permits flow autoregulation by reducing flow with pressure elevation, and permitting dilatation and increased flow with pressure reduction. Each resistance vessel has a different operating range of pressure, 2,7 e.g., rat middle cerebral arteries exhibit myogenic constriction between B60 and 130 mm Hg, 6,8,9 but penetrating arterioles are active between B20 and 140 mm Hg. 10 Outside the autoregulatory range, diameter ( concentrations.…”

“…Since resistance arteries of o200 mm internal diameter are primarily responsible for blood flow regulation, 18 it is essential that the molecular mechanisms that regulate contraction and relaxation of such vessels will be studied directly. Recent advances, particularly improvements in the sensitivity of detection and quantification of protein phosphorylation levels, 8,9,19 have enabled direct analysis of signal transduction pathways involved in the control of contraction and relaxation of smaller vessels, including the myogenic response of cerebral and other resistance arteries.…”