Baskakov Mb

NKCC1 and hypertension: Role in the regulation of vascular smooth muscle contractions and myogenic tone

High-ceiling diuretics (HCD), known potent inhibitors of housekeeping Na+,K+,2Cl cotransporter (NKCC1) and renal-specific NKCC2, decrease [Cl−]i, hyperpolarize vascular smooth muscle cells (VSMC), and suppress contractions evoked by modest depolarization, phenylephrine, angiotensin II, and UTP. These actions are absent in nkcc1 / knock-out mice, indicating that HCD interact with NKCC1 rather than with other potential targets. These findings also suggest that VSMC-specific inhibitors of NKCC1 may be considered potential pharmacological therapeutic tools in treatment of hypertension. It should be underlined that side by side with attenuation of peripheral resistance and systemic blood pressure, HCD blocked myogenic tone (MT) in renal afferent arterioles. Keeping this in mind, attenuation of MT might be a mechanism underlying the prevalence of end-stage renal disease documented in hypertensive African-Americans with decreased NKCC1 activity and in hypertensive patients subjected to chronic HCD treatment. The role of NKCC1-mediated MT in protection of the brain, heart, and other encapsulated organs deserves further investigation.

Vascular Smooth Muscle Contraction Evoked by Cell Volume Modulation: Role of the Cytoskeleton Network

Previously, we reported that hyposmotic swelling evoked transient vascular smooth muscle cell (SMC) contraction that was completely abolished by L-type Ca2+ channel blockers. In contrast, sustained contraction revealed in hyper- and isoosmotically-shrunken SMCs was insensitive to L-type channel blockers and was diminished in Ca2+-free medium by only 30-50%. Several research groups reported cell volume-dependent cytoskeleton network rearrangements. This study examines the role of cytoskeleton proteins in cell volume-dependent contraction of endothelium-denuded vascular smooth muscle rings (VSMR) from the rat thoracic aorta. Hyperosmotic shrinkage and hyposmotic swelling were triggered by modulation of medium osmolality; isosmotic shrinkage was induced by VSMR transfer from hypo- to isosmotic medium. The relative content of globular (G) and fibrillar (F) actin was estimated by fluorescence microscopy. Hyperosmotic shrinkage and hyposmotic swelling led to elevation of the F-actin/G-actin ratio by 2.5- and 1.8-fold respectively. Contraction of shrunken and swollen VSMR was insensitive to modulators of microtubules such as vinblastine, colchicine and docetaxel. Microfilament disassembly by cytochalasin B resulted in dramatic attenuation of the maximal amplitude of contraction of hyperosmotically-shrunken and hyposmotically-swollen VSMR, and almost completely abolished the contraction triggered by isosmotic shrinkage. These data suggest that both L-type Ca2+ channel-mediated contraction of swollen vascular SMC and Ca2+o-insensitive contractions of shrunken cells are triggered by reorganization of the microfilament network caused by elevation of the F-actin/G-actin ratio.

REGULATION OF CONTRACTILE ACTIVITY OF SMOOTH MUSCLE CELLS BY REACTIVE OXYGEN SPECIES: EVIDENCE FOR CYTOSKELETON-MEDIATED SIGNALING: PP.21.344

Objective: Recent studies showed that the cytoskeleton is the primary target of reactive oxygen species (ROS). This study examines the role of cytoskeleton network in regulation of vascular smooth muscle cell contractions by ROS. Design and Methods: Contractile responses of rat aorta strips triggered by depolarization and activation of α1-adrenergic receptors with high K+-medium and phenylephrine, respectively, were measured as increments of isometric tension. Cytoskeleton elements were modified with colchicines (10 μM), cytochalasin D (0,5 μM) and nocodazole (10 μM). Production of ROS was evoked by hydrogen peroxide (500 μM). Results: Hydrogen peroxide increased contractions triggered by high-K+ -medium by 25,2 ± 2,9% (p < 0,05) and reduced the amplitude of phenylephrine-induced contractile responses by 51,7 ± 2,9% (p < 0,05). Colchicine and cytochalasin D, but not nocodazole increased the relaxing effect of hydrogen peroxide in the reduction of phenylephrine-induced contractions by 83,5 ± 4,1% (p < 0,05) and 89,4 ± 2,9% (p < 0,05), respectively, but did not affect modulation by ROS of contractions triggered by depolarization. Conclusion: Our data demonstrate the involvement of cytoskeleton-mediated signaling in regulation by ROS of vascular smooth muscle cell contractions caused by activation of - α1-adrenergic receptors.

EFFECT OF REACTIVE OXYGEN ON MECHANISMS COUPLING EXCITATION OF SMOOTH MUSCLE CELLS GUINEA PIG URETER: PP.21.345

Objective: Reactive oxygen species claim to the role of signaling molecules, especially towards the realization of oxidative stress. However, the methods and extent of their interaction with key intracellular signaling and effector systems of regulation of excitation-coupling in smooth muscle cells continue to actively explored. This study examines the effect of reactive oxygen species in the mechanisms of regulation by cyclic nucleotides and calcium signaling system of electrical and contractile activity of smooth muscle cells. Design and Methods: The method of double sucrose bridge to study the effect of hydrogen peroxide and nitric oxide on electrical and contractile properties of smooth muscle cells of guinea pig ureter, caused by electric stimulus. To investigate the role of C-kinase branch of the calcium and nitric oxide in the development of the action potential and contractile responses of smooth muscle using phenylephrine and sodium nitroprusside, respectively. Results: Found opposite effect of hydrogen peroxide and cyclic nucleotides on C-kinase branch of the regulation of excitation-coupling in smooth muscle cells. With additional activation protenkinase with phenylephrine changing effects of hydrogen peroxide and sodium nitroprusside: electrical and contractile activity are inhibited. Similar effects have evolved against the background of inhibitors of enzymes break down hydrogen peroxide and cyclic nucleotides. Thus, the C-kinase branch of the calcium signaling system is one of the major intracellular targets, the effect on reactive oxygen species that leads to the inhibition of electrical and contractile activity of smooth muscle cells of guinea pig ureter.

Age-related characteristics of epithelial-muscular interactions in the rat trachea

The interactions between epithelial and muscular cells of tracheal wall were studied by a mechanographic technique in rats of different ages. The state of the epithelium was assessed using hematoxylin-eosin stained sections. The epithelium-dependent relaxation was found to be most promounced in 10–12-week-old rats. It was not observed in younger rats probably due to the low sensitivity of guanylate cyclase to activating stimuli. Destructive changes in the respiratory epithelium after 24 weeks of life reduced the amplitude of epithelium-dependent relaxation in old rats.