Reflex vasoconstriction in aged human skin increasingly relies on Rho kinase-dependent mechanisms during whole body cooling

Lang JA, Jennings JD, Holowatz LA, Kenney WL. Reflex vasoconstriction in aged human skin increasingly relies on Rho kinase-dependent mechanisms during whole body cooling. Am J Physiol Heart Circ Physiol 297: H1792-H1797, 2009. First published August 28, 2009; doi:10.1152/ajpheart.00509.2009.-Primary human aging may be associated with augmented Rho kinase (ROCK)-mediated contraction of vascular smooth muscle and ROCK-mediated inhibition of nitric oxide synthase (NOS). We hypothesized that the contribution of ROCK to reflex vasoconstriction (VC) is greater in aged skin. Cutaneous VC was elicited by 1) whole body cooling [mean skin temperature (T-sk) = 30.5 degrees C] and 2) local norepinephrine (NE) infusion (1 X 10(-6) M). Four microdialysis fibers were placed in the forearm skin of eight young (Y) and eight older (O) subjects for infusion of 1) Ringer solution (control), 2) 3 mM fasudil (ROCK inhibition), 3) 20 mM N-G-nitro-L-arginine methyl ester (NOS inhibition), and 4) both ROCK + NOS inhibitors. Red cell flux was measured by laser-Doppler flowmetry over each site. Cutaneous vascular conductance (CVC) was calculated as flux/mean arterial pressure and normalized to baseline CVC (%Delta CVCbaseline). VC was reduced at the control site in O during cooling (Y, -34 +/- 3; and O, -18 +/- 3%Delta CVCbaseline; P < 0.001) and NE infusion (Y, -53 +/- 4, and O, -41 +/- 9%Delta CVCbaseline; P = 0.006). Fasudil attenuated VC in both age groups during mild cooling; however, this reduction remained only in O but not in Y skin during moderate cooling (Y, -30 +/- 5; and O, -7 +/- 1%Delta CVCbaseline; P = 0.016) and was not altered by NOS inhibition. Fasudil blunted NE-mediated VC in both age groups (Y, -23 +/- 4; and O, -7 +/- 3%Delta CVCbaseline; P < 0.01). Cumulatively, these data indicate that reflex VC is more reliant on ROCK in aged skin such that approximately half of the total VC response to whole body cooling is ROCK dependent.