ABSTRACT
BACKGROUND: An increase of the extracellular K+concentrations up to about 8 mM in the isolated vessels causes relaxation in pre-contracted state. In order to elucidate the mechanisms of K+induced relaxation and compare with that of 2-kidney, 1 clip (2K1C) renal hypertensive rats, we recorded aortic vascular tension using an organ bath study. METHOD: 2K1C hypertension was made by clipping the left renal artery and age-matched control rats received a sham treatment. Thoracic aortic rings were mounted in tissue baths for measurement of isometric contractile force. RESULTS: Exposure to K+(from 2 to 8 mM) relaxed a phenylephrine (2 x 10-6 M)-induced contraction in K+free Krebs-Ringer solution, dose-dependently. Ouabain (10-5 M) enhanced the K+induced relaxation in above 2 mM K+ The K+induced relaxation was still induced in endothelium-denuded condition. Incubation with the K+channel blockers such as tetraethylammonium (TEA, 1 mM), glibenclamide (10-5 M), 4-aminopyridine (3 mM), barium (5 mM) and cesium (2 mM) did not affect on the K+induced relaxation. In renal hypertensive rats, the K+induced relaxation was markedly suppressed and ouabain enhanced it. CONCLUSIONS: These results suggest that the K+induced relaxation in aorta be mediated by Na-pump independent mechanisms, and the decrease of the K+induced relaxation in the renal hypertensive rats may be a possible mechanism of hypertension.
Subject(s)
Animals , Rats , 4-Aminopyridine , Aorta , Barium , Baths , Cesium , Glyburide , Hypertension , Muscle, Smooth , Ouabain , Phenylephrine , Placebos , Relaxation , Renal Artery , Tetraethylammonium , VasodilationABSTRACT
BACKGROUND: An increase of the extracellular K+concentrations up to about 8 mM in the isolated vessels causes relaxation in pre-contracted state. In order to elucidate the mechanisms of K+induced relaxation and compare with that of 2-kidney, 1 clip (2K1C) renal hypertensive rats, we recorded aortic vascular tension using an organ bath study. METHOD: 2K1C hypertension was made by clipping the left renal artery and age-matched control rats received a sham treatment. Thoracic aortic rings were mounted in tissue baths for measurement of isometric contractile force. RESULTS: Exposure to K+(from 2 to 8 mM) relaxed a phenylephrine (2 x 10-6 M)-induced contraction in K+free Krebs-Ringer solution, dose-dependently. Ouabain (10-5 M) enhanced the K+induced relaxation in above 2 mM K+ The K+induced relaxation was still induced in endothelium-denuded condition. Incubation with the K+channel blockers such as tetraethylammonium (TEA, 1 mM), glibenclamide (10-5 M), 4-aminopyridine (3 mM), barium (5 mM) and cesium (2 mM) did not affect on the K+induced relaxation. In renal hypertensive rats, the K+induced relaxation was markedly suppressed and ouabain enhanced it. CONCLUSIONS: These results suggest that the K+induced relaxation in aorta be mediated by Na-pump independent mechanisms, and the decrease of the K+induced relaxation in the renal hypertensive rats may be a possible mechanism of hypertension.
Subject(s)
Animals , Rats , 4-Aminopyridine , Aorta , Barium , Baths , Cesium , Glyburide , Hypertension , Muscle, Smooth , Ouabain , Phenylephrine , Placebos , Relaxation , Renal Artery , Tetraethylammonium , VasodilationABSTRACT
OBJECTIVES: Visualization of the left atrial appendage(LAA) by the transesophageal echocardiography(TEE) is excellent, but it is difficult to visualize the LAA by the modified parasternal short-axis view(MPSA) in transthoracic echocardiography(TTE). We studied to determine the usefulness of the apical horizontal view(AHV) abtained by the apical rotation method of the transducer for the detection of the LAA. METHODS: We studied the MPSA and AHV in 602 patients, The LAA was observed during diastole of the LAA. We obtained an apical horizontal view by 45 degree clockwise rotation of the transducer from the apical 2 chamber view and compared with the visualization of the LAA in AHV and MPSA. RESULTS: Among 602 patients, LAA could not be visualized in 88(14.6%) because of a poor echo-window. LAA was more clearly visualized in 222 patients by the AHV than the MPSA and 56 patients by the MPSA than the AHV. LAA was same degree visualization in patients by the AHV and MPSA. In male and female, more than 55 ages and less than 55 ages, visualization of inner margin of the LAA by the AHV was more clear than by the MPSA. CONCLUSION: The AHV was a useful, noninvasive and reproducible method for the visualization of the LAA.