Taenia Cecum Research Articles

Effects of cytochalasin D on relaxation process of skinned taenia cecum and carotid artery from guinea pig

Actin linked regulatory mechanisms are known to contribute contraction/relaxation in smooth muscle. In order to clarify whether modulation of polymerization/depolymerization of actin filaments affects relaxation process, we examined the effects of cytochalasin D on relaxation process by Ca2+ removal after Ca2+-induced contraction of β-escin skinned (cell membrane permeabilized) taenia cecum and carotid artery preparations from guinea pigs. Cytochalasin D, an inhibitor of actin polymerization, significantly suppressed the force during relaxation both in skinned taenia cecum and carotid artery. The data fitting analysis of the relaxation processes indicates that cytochalasin D accelerates slow (latch-like) bridge dissociation. Cytochalasin D seems to directly disrupts actin filament organization or its length, resulting in modulation of actin filament structure that prevents myosin binding.

Accelerating effects of blebbistatin on relaxation process of cell membrane permeabilized trachea and taenia cecum from guinea pig.

Blebbistatin, a potent inhibitor of myosin II, is known to suppress smooth muscle contraction without affecting myosin light chain phosphorylation level. In order to clarify the regulatory mechanisms of blebbistatin on phasic and tonic smooth muscles in detail, we examined the effects of blebbistatin on relaxation process by Ca2+ removal after Ca2+-induced contraction of β-escin skinned (cell membrane permeabilized) trachea and taenia cecum preparations from guinea pigs. Blebbistatin significantly suppressed the force during relaxation both in skinned trachea and taenia cecum. The data fitting analysis of the relaxation processes indicates that blebbistatin accelerates slow (latch-like) bridge dissociation.

Blebbistatin, a myosin II inhibitor, suppresses Ca<sup>2+</sup>-induced and “sensitized”-contraction of skinned tracheal muscles from guinea pig

Blebbistatin, a potent inhibitor of myosin II, has inhibiting effects on Ca2+-induced contraction and contractile filament organization without affecting the Ca2+-sensitivity to the force and phosphorylation level of myosin regulatory light chain (MLC20) in skinned (cell membrane permeabilized) taenia cecum from the guinea pig (Watanabe et al., Am J Physiol Cell Physiol. 2010; 298: C1118–26). In the present study, we investigated blebbistatin effects on the contractile force of skinned tracheal muscle, in which myosin filaments organization is more labile than that in the taenia cecum. Blebbistatin at 10 μM or higher suppressed Ca2+-induced tension development at any given Ca2+ concentration, but had little effects on the Ca2+- induced myosin light chain phosphorylation. Also blebbistatin at 10 μM and higher significantly suppressed GTP-γS-induced "sensitized" force development. Since the force inhibiting effects of blebbistatin on the skinned trachea were much stronger than those in skinned taenia cecum, blebbistatin might directly affect myosin filaments organization.

Blebbistatin, a myosin II inhibitor, suppresses contraction and disrupts contractile filaments organization of skinned taenia cecum from guinea pig

To explore the precise mechanisms of the inhibitory effects of blebbistatin, a potent inhibitor of myosin II, on smooth muscle contraction, we studied the blebbistatin effects on the mechanical properties and the structure of contractile filaments of skinned (cell membrane permeabilized) preparations from guinea pig taenia cecum. Blebbistatin at 10 microM or higher suppressed Ca(2+)-induced tension development at any given Ca(2+) concentration but had little effects on the Ca(2+)-induced myosin light chain phosphorylation. Blebbistatin also suppressed the 10 and 2.75 mM Mg(2+)-induced, "myosin light chain phosphorylation-independent" tension development at more than 10 microM. Furthermore, blebbistatin induced conformational change of smooth muscle myosin (SMM) and disrupted arrangement of SMM and thin filaments, resulting in inhibition of actin-SMM interaction irrespective of activation with Ca(2+). In addition, blebbistatin partially inhibited Mg(2+)-ATPase activity of native actomyosin from guinea pig taenia cecum at around 10 microM. These results suggested that blebbistatin suppressed skinned smooth muscle contraction through disruption of structure of SMM by the agent.

Differential effects of an expected actin-tropomyosin binding region of heat shock protein 20 on the relaxation in skinned carotid artery and taenia cecum from guinea pig

To explore the possible role of heat shock protein 20 (HSP20) -linked regulation of actin-myosin interaction in living vascular smooth muscle contraction, we studied the effects of HSP20p and TnIp, synthetic peptides originating from an actin tropomyosin binding region of human heat shock protein 20 [residues 110-121; GFVAREFHRRYR] and that of rabbit cardiac troponin I [residues 136-147; GKFKRPTLRRVR], respectively, on the active stress and phosphorylation level of myosin regulatory light chain (MLC(20)) during relaxation of skinned (cell membrane permeabilized) preparations from "tonic" carotid artery and "phasic" taenia cecum from guinea pig. Active stress of the skinned preparations, resulting from actin-myosin interaction, biphasically decayed following Ca(2+) removal (relaxation). Decay of MLC(20) phosphorylation level by Ca(2+) removal was much faster than active stress in an exponential manner. In skinned carotid artery, HSP20p did neither affect relaxation time course nor MLC(20) dephosphorylation, whereas, in skinned taenia cecum, the peptide slowed relaxation time course through inhibition of MLC(20) dephosphorylation and slowing "latch"-bridge dissociation. On the other hand, TnIp accelerated relaxation time course without affecting MLC(20) dephosphorylation in both skinned carotid artery and skinned taenia cecum. Our present results suggest that, HSP20p slows the relaxation processes through intracellular regulatory mechanisms such as Rho A/Rho-kinase mediated pathways, which are known to be dominant in "phasic" smooth muscles but to be recessive in "tonic" smooth muscles.

Mechanisms of the inhibitory effects of a phenoxazine compound, 2-amino-4,4.ALPHA.-dihydro-4 .ALPHA.-7-dimethyl-3H-phenoxazine-3-one, on the contraction of the smooth muscle of the guinea pig taenia cecum

To elucidate the mechanisms involved in the relaxing effect of 2-amino-4, 4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one (Phx-1) on smooth muscle, we investigated its effects on the contraction of both intact and skinned (cell membrane permeabilized) preparations from the guinea pig taenia cecum. In intact preparations, Phx-1 concentration-dependently suppressed the contraction induced by either acetylcholine (ACh) or high-K(+) with an IC(50) value estimated at around 100 muM. Similar inhibitory actions of Phx-1 on force were observed in intracellular Ca store depleted preparations. In cell membrane depolarized preparations in the absence of extracellular Ca, however, Phx-1 had little effect on either caffeine- or ACh-induced contractions. In skinned preparations, Phx-1 suppressed Ca(2+)-induced contractions at concentrations higher than 100 muM. These results suggest that inhibition of smooth muscle contraction by Phx-1 is due mainly to inhibition of Ca(2+)-influx, although Phx-1 also seems to have direct inhibitory effects on the activities of the contractile apparatus.

Mechanisms of the Force Inhibitory effects of a Phenoxazine Compound, 2-Amino-4,4α -dihydro-4 α-7-dimethyl-3H-phenoxazine-3-one on the Contraction of Smooth Muscles in Guinea Pig Taenia Cecum

Mechanisms of the Force Inhibitory effects of a Phenoxazine Compound, 2-Amino-4,4α -dihydro-4 α-7-dimethyl-3H-phenoxazine-3-one on the Contraction of Smooth Muscles in Guinea Pig Taenia Cecum

Carteolol is a weak partial agonist on β3-adrenergic receptors in brown adipocytes

The ability of the Beta1/Beta2 partial agonist carteolol to act as an agonist on Beta3-adrenergic receptors was investigated by studying its ability to stimulatethermogenesis (oxygen consumption) in brown fat cells isolated from hamsters. Carteolol wasable to induce thermogenesis, with an EC50 of 5 µM, but it was only a partial(40%) agonist. D,L-Propranolol had a pKB of 5.1 as anantagonist against carteolol in this system, indicating that the carteolol effect was probablymediated via Beta3-receptors. Also in mouse and rat cells, carteolol was a partial agonist withEC50 values around 1 µM. Being a partial agonist, carteolol acted as an antagonistagainst norepinephrine-, BRL-37344-, or CGP-12177-stimulated thermogenesis with apKB of approximately5. The partial agonist effects of carteolol are discussed in relation to the absence of agonisteffect of this compound on guinea-pig taenia cecum Beta3-receptors and in relation to the possible plurality of Beta3-receptors.Key words: carteolol, Beta3-adrenergic receptor, brown fat cells, nonshivering thermogenesis.

Effects of trimebutine on cytosolic Ca 2+ and force transitions in intestinal smooth muscle

The effects of trimebutine maleate on cytosolic free Ca 2+ and force transitions in the guinea-pig taenia cecum were studied by fura-2 fluorometry and tension recording. The addition of 80 mM K + induced a transient increase in cytosolic free Ca 2+ concentration ([Ca 2+] i) and tension, followed by a sustained increase. Trimebutine (10 μM) suppressed both [Ca 2+] i elevation and tension development. The tonic responses were more potently inhibited than the phasic responses. Phasic components gradually increased as the added K + increased (10–40 mM). The relationship between the peak increases in [Ca +] i and tension was not affected by trimebutine (10 μM). This means that trimebutine dose not affect the Ca 2+ sensitivity of contractile elements. In a high K + and Ca 2+-free medium, carbachol (10 μM) or caffeine (30 mM) caused transient [Ca 2+] i elevation and tension development in the smooth muscle. Trimebutine (10 μM) decreased the amplitude of both responses. Trimebutine (10 μM) inhibited the spontaneous fluctuations in [Ca 2+] i and motility of taenia cecum in the presence of tetrodotoxin (TTX; 0.3 μM). These results suggest that trimebutine has two types of inhibitory actions on intestinal smooth muscle; one, the inhibition of Ca 2+ influx through voltage-dependent calcium channels, and the other, the inhibition of Ca 2+ release from intracellular storage sites.

Allosteric interaction of trimebutine maleate with dihydropyridine binding sites

The effects of trimebutine maleate on [ 3H]nitrendipine binding to guinea-pig ileal smooth muscle membranes and Ca 2+-induced contraction of the taenia cecam were studied. Specific binding of [ 3H]nitrendipine to smooth muscle membranes was saturable, with a K D value and maximum number of binding sites (B max) of 0.16 nM and 1070 fmol/mg protein, respectively. Trimebutine inhibited [ 3H]nitrendipine binding in a concentration-dependent manner with a K i value of 9.3 μM. In the presence of trimebutine (10 μM). Scatchard analysis indicated a competitive-like inhibition with a decrease in the binding affinity (0.31 nM) without a chane in B max(1059 fmol/mg protein). However, a dissociation experiment using trimebutine (10 or 100 μM) showed that the decreased affinity was due to an increase of the dissociation rate constant of [ 3H]nitrendipine binding to the membrane. In mechanical experiments using the taenia cecum, trimebutine (3–30 μM) caused a parallel rightward shift of the dose-response curve for the contractile response to a higher concentration range of Ca 2+ under high-K + conditions in a noncompetitive manner. These results suggest that trimebutine has negative allosteric interactions with 1,4-dihydropyridine binding sites on voltage-dependent Ca 2+ channels and antagonizes Ca 2+ influx, consequently inhibiting contractions of intestinal smooth muscle.

Synthesis and calcium ion antagonistic activity of 2-[2-[(aminoalkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H-1,4-benzothiazines

As an extension of the previous investigation (J. Med. Chem. 1988, 31, 919), we synthesized a series of 2-[2-[(aminoalkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H- 1,4-benzothiazines (3) and evaluated their Ca2+ antagonistic activities. Ca2+ antagonistic activity was measured with isolated depolarized guinea pig taenia cecum. On the basis of their potent Ca2+ antagonistic activity, six benzothiazines were selected and further evaluated for their vasocardioselectivity. Among these six compounds, the key compound 15 [3,4-dihydro-2-[5-methoxy-2-[3-[N-methyl-N-[2-[3,4- (methylenedioxy)phenoxy]ethyl]amino]propoxy]phenyl]-4-methyl-3-oxo- 2H-1,4-benzothiazine hydrogen fumarate] was recognized as having the lowest cardioselectivity. Following optical resolution, the absolute configuration of the compound's optically active enantiomer was determined by means of X-ray crystallography of a synthetic precursor (+)-4a. The Ca2+ antagonistic activity of 15 was found to reside primarily in (+)-15 (which was about 7 times more potent than (-)-15). The in vitro study showed that (+)-15 had a low cardioselectivity compared to verapamil and diltiazem. This result suggests that (+)-15 would exhibit less adverse effects due to cardiac inhibition than diltiazem and verapamil in therapeutic use.

Synthesis and calcium antagonistic activity of (+)-(R)- and (-)-(S)-3-acetyl-2-(5-methoxy-2-(4-(N-methyl-N-(3,4,5-trimethoxyphenethyl)amino)butoxy)phenyl)benzothiazoline hydrochloride.

SA2572 ((+)-1), 3-acetyl-2-[5-methoxy-2-[4-[N-methyl-N-(3,4,5-trimethoxyphenethyl) amino] butoxy]phenyl]-benzothiazoline hydrochloride is a newly synthesized Ca2+ antagonist having a inhibitory effect on the fast Na+ inward channel. In order to clarify the absolute configurations and the pharmacological properties of both enantiomers, compounds ((+)-1 and (-)-1) were synthesized. The configurations of these compounds were assigned on the basis of an X-ray crystallographic analysis of synthetic precursor (5). The in vitro Ca2+ channel blocking activities of (+)-1 and (-)-1 were evaluated in terms of the inhibitory activities on depolarization-induced contraction of guinea pig taenia cecum and rabbit aorta. The in vivo efficacy of the enantiomers was evaluated with their hypotensive effects in spontaneously hypertensive rats. Compound (-)-1 showed more potent Ca2+ antagonistic activities on guinea pig taenia cecum and rabbit aorta and the hypotensive effect than those activities of (+)-1. In the electrophysiological study of Langendorff perfused rabbit hearts, compound (+)-1 showed more potent inhibitory effect on the fast Na+ inward channel than that of compound (-)-1, and an approximately equal potent inhibitory effect on the slow Ca2+ inward channel as compared with compound (-)-1. Stereoselectivity of the pharmacological activity was found.

Mechanical and electrical activities of cold-stored taenia cecum with rewarming.

ARTICLESMechanical and electrical activities of cold-stored taenia cecum with rewarmingH Fukuda, and S ShibataH Fukuda, and S ShibataPublished Online:01 May 1974https://doi.org/10.1152/ajplegacy.1974.226.5.1060MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByEffect of prolonged cold storage on the mechanical activity of rabbit atriaGeneral Pharmacology: The Vascular System, Vol. 14, No. 4RESPONSIVENESS AND HIGH-ENERGY PHOSPHATEMETABOLISM OF ISOLATED DOG CORONARY ARTERIESJapanese Journal of Pharmacology, Vol. 29, No. 4Adrenergic mechanism in cold stored taenia caecum after rewarmingEuropean Journal of Pharmacology, Vol. 43, No. 1 More from this issue > Volume 226Issue 5May 1974Pages 1060-1065 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.226.5.1060PubMed4824857History Published online 1 May 1974 Published in print 1 May 1974 Metrics