- Characteristics of Potassium Channel in the Isolated Rat Detrusor Muscle.
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Myeong Soo Jang, Eun Mee Choi, Jeoung Hee Ha, Kang Youn Lee, Won Joon Kim
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Yeungnam Univ J Med. 1994;11(2):363-374. Published online December 31, 1994
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DOI: https://doi.org/10.12701/yujm.1994.11.2.363
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 Abstract
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- The purpose of this study was to investigate the characteristics or the potassium channels existing in the rat urinary bladders. Smooth muscle strips of rat detrusor urinae were examined by isometric myography. Relaxation responses of detrusor muscle strips to the three potassium channel openers pinacidil, a cyanoguanidine derivative, BRL 38227, a benzopyran derivative and RP 52891, a tertrahydrothiopyran derivative were examined. The potassium channel openers reduced the basal tone, and the rank order of potency was RP 52891>pincidil>BRL 38227. Procaine, an inhibitor of the voltage-sensitive potassium channel tended to increase the basal tone, but it did not affect the relaxant effects of the calcium-activated potassium channel opener did not antagonize the relaxant effects, but it reduced the Emax of RP 52891 and BRL 38227. Glibenclamide, an inhibitor of the ATP-sensitive potassium channel, antagonized the relaxant effects of pinacidil, RP 52891 and BRL 38227 reducing the Emax of RP 52891 and BRl 38227. Galanin which inhibits secretion of insulin through opening the ATP-sensitive potassium channels in pancreatic β-cells rather increased the basal tone of the isolated detrusor strips. These results suggest that the urinary bladder of the rat has mainly the ATP-sensitive, glibenclamide sensitive potassium channel, which is a different type from that in the pancreatic β-islet cells.
- Effect of GABA on the Contractility of Canine Trachealis Muscle.
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Cheol Hoe Koo, Oh Chul Kwon, Eun Mee Choi, Kang Youn Lee, Won Joon Kim
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Yeungnam Univ J Med. 1994;11(2):314-322. Published online December 31, 1994
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DOI: https://doi.org/10.12701/yujm.1994.11.2.314
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- This study aimed to investigate the existence of GABA receptor and the mechanisms of action of GABA and diazepam of the trachealis muscle isolated from dog. Horizontal muscle strips of 2mm×15mm were prepared from canine trachea, and isometric myography in isolated muscle chamber bubbled with 95/5%-O₂/CO₂ at 36℃, at the pH of 7.4 was performed. Muscle strips contracted responding to the electrical field stimulation (ESP) by 2~20 Hz, 20 msec, monophasic square wave of 60 VDC. GABA and diazepam suppressed the EFS-induced contractions to the similar extent, significantly. (p<0.05). Bicuculline, a GABA(A) receptor antagonist blocked both GABA- and diazepam-inhibitions; but DAVA, a GABA(B) receptor antagoinst did not affect either of them. These results suggest than in the canine trachealis muscle, there may be only GABA(A) receptor, and GABA and diazepam inhibit the contractility via GABA(A) receptor.
- Effect of Imipramine on the Contractility of Single Cells Isolated for Canine Detrusor.
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Chan Wook Huh, Kang Youn Lee, Won Joon Kim
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Yeungnam Univ J Med. 1994;11(2):293-302. Published online December 31, 1994
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DOI: https://doi.org/10.12701/yujm.1994.11.2.293
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Abstract
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- The objective of this study was to establish a good methodology to isolate single smooth muscle cells that are alive and respond properly to pharmacological agents. Canine urinary bladders were employed as the source of single cells, and acetylcholine, atropine and imipramine were used as indicators of pharmacological responsiveness. Imipramine, an antidepressant drug exhibited the anticholinergic and calcium antagonizing properties on rat detrusor muscle. To establish a control value for a further experiment to elucidate the mechanism of action of imipramine on detrusor muscle, we measured the concentration-response of single cells to acetylcholine in the presesnce of imipramine by length of the cells and compared the result with the response in the presence of atropine. Tiny chops of smooth muscle taken from anesthetized canine urinary bladder were incubated in collagenase solution at 36℃ for 17-20 minutes. The collagenase solution included collagenase 1.2 mg/ml, soybean tryspin inhibitory 0.08 mg/ml, bovine serum albumin 2% in 10 ml Krebs-Henseleit buffer solution aerated with a consistent breeze of 95/5% O2/CO2 to maintain the pH at 7.4. After washing with plain K-H solution on 450 mesh, cells were dissociated from the digested tissue for 12-15 minutes. Cell suspension was transfered in 5 ml test tubes and acetylcholine was added for the final concentration to be 10⁻¹⁴~10⁻⁹M. To find the optimal time to fix the cells to determine the contractile responses, 1% acrolein was added 5, 10, 20, 30, 60 and 120 seconds after the administration of ACh. The length of cells fixed by acrolein were measured by microscaler vis CCTV camers on phaes-contrast microscope. The average length of 50 cells from a slide glass was taken as the value of a sample at the very concentration point. Single cells were isolated from canine detrusor. The length of untreated cells varied from 82 µm to 94 µm. The maximal response to actylcholine 10E-9M was accomplished within 5 seconds of exposure, and the shortening was 19±3%. Atropine reduced the contraction of the cells concentration-dependently. Lmipramine which exerts a cholinergic blocking action on some smooth muscles also reduced the contraction concentration-dependently and by a similar pattern as atropine. These findings document that imipramine may exerts a cholinergic blocking activity in the single smooth muscle cells isolated from canine urinary bladder.
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Yeungnam University College of Medicine
