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Mechanisms of the Ba2+-induced contraction in smooth muscle cells of the rabbit mesenteric artery.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Satoh, Shigeki Kubota, Yuko Itoh, Takehiko Kuriyama, Hirosi |
| Copyright Year | 1987 |
| Abstract | The mechanism of the Ba2+-induced contraction was investigated using intact and saponin-treated skinned smooth muscle (skinned muscle) strips of the rabbit mesenteric artery. After depletion of Ca2+ stored in the caffeine-sensitive site, greater than 0.65 mM Ba2+ evoked contraction in muscle strips depolarized with 128 mM K+ in Ca2+-free solution in a dose-dependent fashion, and the ED50 values for Ca2+ and Ba2+ were 0.5 mM and 1.2 mM in intact muscle strips, respectively. Nisoldipine (10 nM) blocked the contraction evoked by high K+ or 10 microM norepinephrine (NE) in the presence of 2.6 mM Ba2+, but did not block the contraction evoked in the presence of 2.6 mM Ca2+. These results may indicate that Ba2+ permeates the voltage-dependent Ca2+ channel. In skinned muscle strips, the ED50 values for Ca2+ and Ba2+ were 0.34 and 90 microM, respectively, as estimated from the pCa- and pBa-tension relationships. Calmodulin enhanced and trifluoperazine inhibited the Ba2+- and Ca2+-induced contractions. After the application of Ba2+ or Ca2+ with ATP gamma S in rigor solution, myosin light chain (MLC) was irreversibly thiophosphorylated, as estimated from the Ba2+- or Ca2+-independent contraction. Furthermore, both divalent cations phosphorylated MLC, as measured using two-dimensional gel electrophoresis, to the extent expected from the amplitudes of the contraction evoked by these cations. Thus, Ba2+ is capable of activating the contractile proteins as Ca2+ does. The amount of Ca2+ or Ba2+ stored in cells was estimated from the caffeine response evoked in Ca2+-free solution in intact and skinned muscle strips. After the application of 0.3 microM Ca2+ or 0.1 mM Ba2+ for 60 s to skinned muscle strips after the depletion of Ca2+ stored in cells, caffeine produced a contraction only upon pretreatment with Ca2+ but not with Ba2+. When Ba2+ was applied successively just after the application of Ca2+, the subsequently evoked caffeine-induced contraction was much smaller than that evoked by pretreatment with Ca2+ alone. The above results indicate that Ba2+ permeates the voltage-dependent Ca2+ channel but may not permeate the receptor-operated Ca2+ channel, it releases Ca2+ from store sites but is not accumulated into the store site, and it directly activates the contractile proteins via formation of a Ba2+-calmodulin complex. |
| Starting Page | 340 |
| Ending Page | 344 |
| Page Count | 5 |
| File Format | PDF HTM / HTML |
| PubMed reference number | 3559513v1 |
| Volume Number | 89 |
| Issue Number | 2 |
| Journal | The Journal of general physiology |
| Alternate Webpage(s) | http://jgp.rupress.org/content/jgp/89/2/215.full.pdf |
| Alternate Webpage(s) | http://ftp.ncbi.nlm.nih.gov/pub/pmc/b1/a8/jg892215.PMC2215898.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Adenosine Triphosphate Brodmann area 2 Caffeine Calcium ion Cations Cations, Divalent Contractile Proteins Electrophoresis, Gel, Two-Dimensional Gel Electrophoresis (lab technique) Mesenteric Arteries Mesentery Muscle Cells Muscle Rigidity Myocytes, Smooth Muscle Myosin Light Chains Nisoldipine Norepinephrine Potassium Proteiniborus sp. BA2-13 Saponin Skin Small Smooth muscle (tissue) Tension Trifluoperazine strip medical device |
| Content Type | Text |
| Resource Type | Article |
