RHO KINASE PROMOTES ENHANCED TONE IN CONTRACTILE LYMPHATICS.
Document Type
Presentation
Start Date
22-10-2010 3:00 PM
End Date
22-10-2010 4:30 PM
Description
To perform their functions in fluid and solute homeostasis, lipid absorption, and immunity, lymphatic vessels must transport lymph through the lymphatic network, nodes, and back to the great veins of the central circulation. The contractile nature of collecting lymphatics is a central feature that determines the rate of lymph flow. In contrast to blood vessels, lymphatic vessels propel lymph using both tonic and phasic contractions. The influence of pressure and flow on lymphatic contractility has been characterized, but the cellular and molecular mechanisms that underlie lymphatic contractile patterns are poorly understood. We hypothesized that like in vascular smooth muscle, Rho kinase (ROCK) signaling enhances tonic constriction of lymphatic smooth muscle. To test our hypothesis, we inhibited ROCK activity in isolated rat collecting lymphatics using two structurally distinct pharmacologic blockers, Y-27632 (0.5-5 μM) and ROCK Inhibitor V (0.01-10 μM). The spontaneous contractile activity the lymphatics was observed in a 37 °C albumin physiological salt solution (APSS) bath, at a luminal pressure of 2 cm H20. We used a tracking video caliper to record end diastolic diameter (EDD), end systolic diameter (ESD), and contraction frequency (CF). At the end of each experiment, the bath solution was changed to a calcium-free APSS to determine the passive maximal diameter (MaxD). We also calculated the phasic contraction amplitude (AMP= EDD-ESD) and tone [(MaxD-EDD)/MaxD)*100%]. Y-27632 and ROCK Inhibitor V both significantly increased EDD and ESD in a dose-dependent manner. These changes were associated with significantly decreased lymphatic tone at 5 μM Y-27632 (13.5 ± 6.3 % vs. control: 22.5 ± 4.1 %, P<0.05) and both 1 μM and 10 μM Rho Kinase Inhibitor V (1 μM: 10.4 ± 2.1 and 10 μM: 7.2 ± 2.5 vs. control: 23.1 ± 3.1, both P<0.05), but no changes in mean AMP. Y-27632 (5 μM) also significantly decreased CF, but the decrease in CF with ROCK Inhibitor V was not significant (P=0.11 ). Our data suggest that ROCK signaling promotes tonic contractile activity of lymphatics, and although ROCK may have some impact on phasic contractions, these appear to be indirect effects on phasic contractile activity. Supported by NIH 5P20RR018766 and a grant from the American Heart Association. 55
Recommended Citation
Kurtz, Kristine; Souza-Smith, F. M.; and Breslin, J. W., "RHO KINASE PROMOTES ENHANCED TONE IN CONTRACTILE LYMPHATICS." (2010). Dr. Joseph M. Moerschbaecher, III Graduate Research Day. 11.
https://digitalscholar.lsuhsc.edu/grad_rs/2010/poster2/11
RHO KINASE PROMOTES ENHANCED TONE IN CONTRACTILE LYMPHATICS.
To perform their functions in fluid and solute homeostasis, lipid absorption, and immunity, lymphatic vessels must transport lymph through the lymphatic network, nodes, and back to the great veins of the central circulation. The contractile nature of collecting lymphatics is a central feature that determines the rate of lymph flow. In contrast to blood vessels, lymphatic vessels propel lymph using both tonic and phasic contractions. The influence of pressure and flow on lymphatic contractility has been characterized, but the cellular and molecular mechanisms that underlie lymphatic contractile patterns are poorly understood. We hypothesized that like in vascular smooth muscle, Rho kinase (ROCK) signaling enhances tonic constriction of lymphatic smooth muscle. To test our hypothesis, we inhibited ROCK activity in isolated rat collecting lymphatics using two structurally distinct pharmacologic blockers, Y-27632 (0.5-5 μM) and ROCK Inhibitor V (0.01-10 μM). The spontaneous contractile activity the lymphatics was observed in a 37 °C albumin physiological salt solution (APSS) bath, at a luminal pressure of 2 cm H20. We used a tracking video caliper to record end diastolic diameter (EDD), end systolic diameter (ESD), and contraction frequency (CF). At the end of each experiment, the bath solution was changed to a calcium-free APSS to determine the passive maximal diameter (MaxD). We also calculated the phasic contraction amplitude (AMP= EDD-ESD) and tone [(MaxD-EDD)/MaxD)*100%]. Y-27632 and ROCK Inhibitor V both significantly increased EDD and ESD in a dose-dependent manner. These changes were associated with significantly decreased lymphatic tone at 5 μM Y-27632 (13.5 ± 6.3 % vs. control: 22.5 ± 4.1 %, P<0.05) and both 1 μM and 10 μM Rho Kinase Inhibitor V (1 μM: 10.4 ± 2.1 and 10 μM: 7.2 ± 2.5 vs. control: 23.1 ± 3.1, both P<0.05), but no changes in mean AMP. Y-27632 (5 μM) also significantly decreased CF, but the decrease in CF with ROCK Inhibitor V was not significant (P=0.11 ). Our data suggest that ROCK signaling promotes tonic contractile activity of lymphatics, and although ROCK may have some impact on phasic contractions, these appear to be indirect effects on phasic contractile activity. Supported by NIH 5P20RR018766 and a grant from the American Heart Association. 55
Comments
See abstract book page 55