Biomedical subjects

T Kitazawa

Publications and source records attributed to T Kitazawa.

At least 55 records · Page 3Linked to original sources

PubMed1997

Functional characterization of neural and smooth muscle motilin receptors in the chicken proventriculus and ileum.

To characterize the motilin receptors present in the chicken, the effects of chicken motilin (Phe-Val-Pro-Phe-Phe-Thr-Gln-Ser-Asp-Ile-Gln-Lys-Met-Gln-Glu-Lys-Glu-Arg -Asn-Lys-Gly-Gln), Leu13 porcine motilin, canine motilin and three erythromycin derivatives (EMA, EM523, GM611) on the contractility of the chicken gastrointestinal (GI) smooth muscles were investigated in vitro and compared with those in the rabbit duodenum. In the proventriculus longitudinal and circular muscle layers, chicken motilin (3 nM-1 microM) caused an atropine- and a tetrodotoxin-sensitive contraction (EC50 = 39-49 nM), and potentiated the EFS-induced contraction without affecting the responsiveness of acetylcholine. EM523 and GM611 (3-100 microM) contracted the proventriculus longitudinal muscle, and the maximum amplitudes of contraction were about 60% of that induced by chicken motilin. Chicken motilin (0.1 nM-100 nM) also caused contraction of the ileum (EC50 = 7 nM) through direct action on the smooth muscle cells. On the other hand, erythromycin derivatives showed only a weak contractile efficacy (about 20% of the maximum response of chicken motilin) even at high concentrations (10-100 microM). The rank order of potency in the ileum was chicken motilin > canine motilin > or = Leu13 porcine motilin > > GM611 > or = EM523 > or = EMA. GM109 slightly inhibited the ideal contractions induced by Leu13 porcine motilin at 100 microM (pA2 = 3.86). In the rabbit duodenum, chicken motilin was a full agonist with the same intrinsic activity as Leu13 porcine motilin, canine motilin and the erythromycin derivatives. However, the rank order of potency (Leu13 porcine motilin > or = canine motilin > chicken motilin > GM611 > or = EM523 > EMA) was different from that in the chicken ileum. In conclusion, chicken motilin causes an excitatory response in the chicken GI tract through activation of neural (proventriculus) and smooth muscle motilin receptors (ileum). The motilin receptor present in the ileum is different from that demonstrated in the rabbit intestine, because of a different rank order of motilin peptides in producing the contraction, low contracting activity of erythromycin derivatives and low antagonistic efficacy of GM109. Different pharmacological characteristics of the mechanical response induced by motilin peptides and erythromycin derivatives between the proventriculus and the ileum are discussed.

Animals↗

PubMed1997

Non-genomic mechanism of 17 beta-oestradiol-induced inhibition of contraction in mammalian vascular smooth muscle.

17 beta-Oestradiol (E2) at 0.1-10 microM directly inhibited various tonic and phasic smooth muscle contractions. The mechanism(s) of oestrogen-induced inhibition of contraction was studied using intact and permeabilized strips and isolated single cells of smooth muscle. 2. In endothelium-denuded vascular smooth muscle, E2 attenuated high K(+)-induced force development and myosin light chain phosphorylation, and produced rapid and reversible relaxation. There were no significant differences in these inhibitory effects between tissue types (femoral artery vs. portal vein), species (rat vs. rabbit) or sexes. 3. The inhibitory potencies of several steroidal and non-steroidal oestrogen analogues were examined and their effects were for the most part stereo-specific. However, two steroids with negligible affinities for the nuclear oestrogen receptor also strongly inhibited high K(+)-induced contraction. 4. Genomic modulators including a protein synthesis inhibitor, an RNA synthesis inhibitor, and oestrogen receptor antagonists did not affect the inhibitory actions of E2. Inhibitors of cyclic nucleotide-dependent protein kinases did not reduce the E2 effect. 5. Ca2+ release from intracellular stores by agonists and by inositol 1,4,5-trisphosphate (IP3) does not appear to be modulated by E2. Neither pretreatment with ryanodine nor with thapsigargin affected the E2-induced inhibition of high K(+)-induced contraction. 6. E2 had no effect on either normal or GTP gamma S-increased Ca2+ sensitivity of the regulatory and contractile apparatus. 7. E2 and its analogues rapidly inhibited voltage-dependent L-type Ca2+ channel currents in isolated smooth muscle cells. Repetitive stimulation was not required for E2-induced inhibition of the currents. 8. This study strongly suggests that at pharmacological concentrations oestrogen primarily reduces Ca2+ influx through inhibition of L-type Ca2+ channels in a non-genomic manner and decreases myosin light chain phosphorylation and contraction of smooth muscle.

Animals↗

PubMed1997

Cyclic GMP causes Ca2+ desensitization in vascular smooth muscle by activating the myosin light chain phosphatase.

Using permeabilized, arterial smooth muscle strips where membrane-associated pathways remain intact but intracellular Ca2+ stores are depleted, we investigated mechanism(s) for the Ca2+ desensitization of contractile force by cGMP. The nonhydrolyzable analog 8-bromo-cGMP, when applied to these strips with submaximal Ca2+ levels clamped, dramatically and reversibly reduced the steady state levels of phosphorylation at 20-kDa myosin light chain and contractile force, with a nanomolar concentration required to obtain 50% reduction. Supramaximal concentrations of 8-bromo-cGMP (10 microM), however, did not change the steady state relationship between phosphorylation and force. When light chain phosphatase activity was blocked at pCa 6.7, 10 microM 8-bromo-cGMP did not affect the rates of rise of light chain phosphorylation and contractile force. When light chain kinase activity was blocked, 10 microM 8-bromo-cGMP significantly accelerated light chain dephosphorylation and force relaxation from the maximal contraction steady state. The light chain phosphorylation time course of a pCa 6. 0-induced contraction in the presence of 8-bromo-cGMP exhibited kinetics that are predictable from a mathematical model in which only light chain phosphatase activity is increased. The results of this study strongly suggest that cGMP indirectly activates light chain phosphatase, the first proposed mechanism for cGMP-induced Ca2+ desensitization in vasodilatation.

Animals↗

PubMed1997

Melanotic cerebral astrocytoma: case report and literature review.

We describe the case of 47-year-old man with a cystic, melanotic temporal lobe astrocytoma who had a history of complex partial seizures. The tumor mass was made up of two histologically different regions: one consisted of spindle-shaped and pleomorphic cells often with foamy or vacuolated cytoplasm, while the other consisted of fairly uniform spindle-shaped cells, many of which contained dark-brown intracytoplasmic pigment. Desmoplasia was also noted in the latter region of the tumor. No features suggestive of malignancy, such as mitotic figures, necrotic foci or endothelial vascular proliferation, were observed throughout the tumor. Immunohistochemically, the tumor cells in both regions were positive for glial fibrillary acidic protein. Ultrastructural examination of the pigmented region showed the presence of melanosomal melanin in the tumor cells. Apart from the partial pigmentation, the entire histological picture resembled a pleomorphic xanthoastrocytoma. To our knowledge, only two cases of similar melanotic astrocytic tumors have been described previously. Interestingly, the astrocytic tumors in both of these patients were also clinically associated with epilepsy, were located in the temporal lobe, and were histologically benign.

Astrocytoma↗

PubMed1997

Histamine mediates the muscle layer-specific responses in the isolated swine myometrium.

To clarify the role of histamine in uterine contractility, the effect of this biogenic amine on the myometrium of cyclic mature gilts was investigated by an isometric tension recording study in vitro. In addition, using crude membrane preparations isolated from the longitudinal (LM) and circular muscle (CM), the distribution of H1 histamine receptors was characterized by 3H-pyrilamine binding assay. Histamine caused a tetrodotoxin-resistant contractile response of LM and CM in Krebs solution, but LM (-logEC50 = 6.34) was more sensitive than CM (-logEC50 = 5.4). Pyrilamine decreased the excitatory response of histamine in both muscle layers. In pyrilamine-treated LM, a high concentration of histamine (1-30 microM) caused a slight inhibition of spontaneous contraction, and this inhibition was abolished by ranitidine. On the other hand, histamine did not cause any inhibition in the pyrilamine-treated CM preparations. Dimaprit (10-300 microM) concentration-dependently inhibited the spontaneous contraction of LM but not of CM. In the presence of pyrilamine and ranitidine, N alpha-methylhistamine, even at 10 microM, did not affect the spontaneous and electrical field stimulation (5Hz)-induced contraction of LM and CM layers. Specific 3H-pyrilamine binding sites were distributed heterogeneously in the swine myometrium. The maximum number of binding sites in LM (132.5 +/- 9.9 fmol/mg protein, n = 10) was 2.5 times higher than that in CM (52.2 +/- 3.2 fmol/mg protein, n = 6). These results indicate that there is a muscle layer-dependent difference of histamine-induced response in the swine myometrium. In the LM layer, histamine acts on both H1 and H2 histamine receptors, and causes contraction (via H1 receptors at a low concentration) or relaxation (via H2 receptors at a high concentration in the presence of pyrilamine). However, histamine causes only a contraction in the CM layer, likely the result of the absence of H2 histamine receptors. Histamine-induced contraction is conspicuous in the LM layer, because of the heterogeneous distribution of H1-receptors between LM and CM.

Animals↗

PubMed1996

Does motilin stimulate the gastrointestinal motility of the pig? In vitro study using smooth muscle strips and dispersed muscle cells.

To clarify the physiological role of motilin in the pig gastrointestinal (GI) tract, effect of Leu13-porcine motilin (LMT) on the contractility of GI smooth muscle was investigated in studies using isolated muscle strips and dispersed muscle cells. LMT produced no contraction in either longitudinal muscle (LM) or circular muscle (CM) of the stomach (fundus, corpus, antrum), duodenum, ileum and colon even at 1 microM. Pretreatment with LMT (1 nM-1 microM) did not potentiate the contractile response to acetylcholine (ACh) in each muscle strip. Dispersed cells from the duodenum responded to ACh in a concentration-dependent manner (EC50 = 10 pM), but not to LMT even at a high concentration (10 microM). Electrical field stimulation (EFS) caused a frequency-dependent (0.2-10 Hz) contraction of the duodenal LM that was almost completely inhibited by atropine or tetrodotoxin. EFS caused the relaxation of duodenal CM in a frequency-dependent manner (0.1-10 Hz). This relaxation was not inhibited by atropine, propranolol, phentolamine or guanethidine, indicating the involvement of noncholinergic, nonadrenergic (NCNA) nerves. NG-nitro L-arginine methylester (L-NAME, 100 microM) attenuated the EFS-induced relaxation and the inhibition at low frequency was larger than that at high frequency. L-Arginine prevented the inhibition by L-NAME but D-arginine did not. LMT (1 nM-1 microM) had no influence on EFS-induced cholinergic contraction of LM and EFS-induced NCNA relaxation of CM layer. The present in vitro studies indicate that motilin is ineffective in producing contraction and in modulating the autonomic neuroeffector transmission of the pig GI smooth muscle, and suggest that pig GI smooth muscle lacks functional motilin receptors.

Acetylcholine↗

PubMed1996

Effects of age on endometrial carcinogenesis induced by concurrent oral administration of ethylenethiourea and sodium nitrite in mice.

Aging effects on the susceptibility to chemical endometrial carcinogenesis were investigated in ICR female mice. The animals were divided into 3 groups of different ages: 1 month (young), 6 months (middle), and 12 months (old) at initiation of treatment. They received weekly oral administration of mixture of ETU (100 mg/kg body weight) and sodium nitrite (70 mg/kg body weight) for 6 months followed by a withdrawal period of 3 months. All animals were subjected to histopathology. The incidence of endometrial adenocarcinomas was highest in the middle age group (8/20), secondary in the old age group (4/20), and lowest in the young group (1/20). The incidence of atypical glandular hyperplasia, a precursor lesion of the tumor, was also higher in the middle age group. The endometrial adenocarcinomas showed morphological similarities among all age groups and the nuclei of tumor cells lost almost all staining reactivity to estrogen receptors. The labeling indices with bromodeoxyuridine (BrdU) were notably higher in the old age group than in the young and middle age groups. A further investigation on the aging process of female genital organs in control mice revealed that their senility seemed to be preceded by the formation of ovarian cysts which first appeared at 6 months of age with a concomitant elevation of plasma 17 beta-estradiol level. These results indicate that the susceptibility of the mouse endometrium to the carcinogenic effects of N-nitroso ETU could be closely linked with the stage of aging process of the genital organs and it appears to be most susceptible when initiated at around 6 months of age. However, the mitotic activity of neoplastic endometrial glandular cells seems to be higher in older mice than younger ones.

Administration, Oral↗

PubMed1996

How to harvest a septal chondromucosal graft.

A simple technique to facilitate easier harvesting of a septal chondromucosal graft is presented. Turning over the ala (like a swinging door) using a perialar incision greatly helps easy harvesting of the graft under extremely good direct vision.

Adult↗

PubMed1995

17beta-Estradiol inhibits the voltage-dependent L-type Ca2+ currents in aortic smooth muscle cells.

To elucidate the mechanisms of estrogens-induced relaxation effects on vascular smooth muscle cells, the effects of estrogens and the related hormones were examined in cultured rat thoracic aortic smooth muscle cell lines (A7r5), using the whole-cell voltage clamp technique. The patch pipette was filled with 140 mM CsCl- or KCl-containing internal solution. With CsCl-internal solution, 17beta-estradiol and synthetic estrogens, ethynylestradiol and diethylstilbestrol (0.1-30 mu M) inhibited the Ba2+ inward current (IBa) through the voltage-dependent L-type Ca2+ channel in a concentration-dependent and reversible manner. The potency of the inhibitory effects on IBa was 17beta-estradiol < ethynylestradiol < diethylstilbestrol. 17beta-Estradiol (10 mu M) appeared to reduce the maximal conductance of IBa with only a slight shift of voltage-dependency of inactivation and to affect IBa in a use-independent fashion. On the other hand, testosterone and progesterone (30 mu M) failed to affect IBa. At a holding potential of -40 mV, both vasopressin and endothelin-1 (100 nM) activated a long-lasting inward current. After endothelin-1 (100 nM) activated the current, the additional application of vasopressin (100 nM) could not induce it furthermore, suggesting that each agonist activates the same population of the channels. The reversal potential of the current was about 0 mV and was not significantly altered by replacement of [Cl-]i or [Cl-]0 and the inward current was also observed even when extracellular cations are Ca2+, proposing that it was a Ca2+-permeable non-selective cation channel (IN.S.). La3+ or Cd2+ (1 nM) completely abolished IN.S., however, nifedipine (10 mu M) failed to inhibit it at all. Diethylstilbestrol (1-30 mu M) suppressed the IN.S. evoked by both endothelin-1 and vasopressin in a concentration-dependent manner, while 17beta-estradiol, ethynylestradiol, progesterone and testosterone (30 mu M) failed to inhibit it significantly. In addition, at a holding potential of +0 mV, 17beta-estradiol by itself did not affect the holding currents, and did not inhibit K+ currents evoked by endothelin-1 or vasopressin, possibly due to the Ca2+ release from the storage sites. These results suggest that 17beta-estradiol may play a role in regulating vascular tone, selectively by inhibiting the voltage-dependent L-type Ca2+ current in vascular smooth muscle cells.

Animals↗

PubMed1995

Excitatory action of [Leu13]motilin on the gastrointestinal smooth muscle isolated from the chicken.

The effects of a porcine motilin analogue, [Leu13]motilin (LMT) on the smooth muscle preparations isolated from the chicken gastrointestinal (GI) tract were investigated in vitro. In the proventriculus, LMT (100 nM to 30 microM) caused an atropine-sensitive contraction and enhanced the electrical field stimulation (EFS)- or 1,1-dimethyl-4-phenyl-piperazinium (DMPP)-induced contraction without affecting the response to acetylcholine (ACh). LMT also caused a concentration-dependent contraction of the intestinal tract (duodenum, jejunum, ileum, and colon). The responsiveness to LMT was strongest in the jejunum and weakest in the colon. The responses to LMT in the intestinal segments were not affected by tetrodotoxin, atropine, hexamethonium, pyrilamine, spantide, and 5-hydroxyltryptamine-induced desensitzation, but significantly decreased by verapamil or removal of external Ca2+. LMT did not enhance the EFS- or DMPP-induced contraction in the ileum. Canine motilin also contracted the intestinal segments in a similar concentration range to LMT with an equal potency, but erythromycin A (EMA) and N-ethyl-N-demethyl-8,9-anhydroerythromycin A, 6-9-hemiketal (EM523) showed only a weak contractile activity even at high concentration (up to 100 microM), indicating that motilin receptors in the chicken intestine were somewhat different from those of mammals. In conclusion, LMT produces an excitatory response in the chicken GI tract with a different sensitivity from region to region. The mechanisms of the action were different between the proventriculus and small intestine; that is, LMT contracts the small intestine through the direct action on the smooth muscle cells, but this peptide acts on the enteric cholinergic neurones and stimulates ACh release, and thus regulates autonomic neuroeffector transmission in the proventriculus.

Acetylcholine↗

PubMed1995

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--III.

Recently, we reported that a ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. We have also found that introduction of substituents such as benzyl or 4-fluorobenzyl (i.e., giving 3 or 4) at the N-3 position of the moiety (A) significantly increased this activity. In this study, novel 2-imidazolidinylidene propanedinitrile derivatives possessing a thioether 5-15 were prepared and evaluated for in vitro assays; acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically induced contractions of guinea pig ileum. Compound 5, in which a nitrogen atom of compound 2 was replaced by a sulfur atom, was more potent than 2 in these tests. Also, in a series of thioether derivatives, introduction of substituents at the N-3 position of the 2-imidazolidinylidene propanedinitrile moiety markedly influenced both activities. In particular, compounds 12 and 13, which showed an excellent potency during in vitro study (AChE IC50 = 3.6 and 2.7 nM; ES. EC30 = 2.1 and 2.5 nM, respectively), were found to be more active in the enhancement of gastrointestinal motility in anesthetized rabbits than their corresponding parent compounds 3 and 4, respectively. In addition, compounds 12 and 13 showed lower affinity for the histamine H2-receptor than ranitidine. Therefore, these compounds may be potent and selective stimulators of gastrointestinal motility.

Acetylcholinesterase↗

PubMed1995

Recovery of gastrointestinal motility from post-operative ileus in dogs: effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha.

Cyclical motor activity of the gastrointestinal tract, normally occurring during the interdigestive period in several mammals, is disrupted in the post-operative ileus. We determined the recovery from the disappearance of cyclical motor activity, from the stomach to the colon, in dogs after laparotomy with the force transducers. Moreover, we examined the effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha (PGF2 alpha), administered in the early post-operative period, on the gastrointestinal motility. Following laparotomy, the cyclical motor activity reappeared firstly in the ileum and the colon, then in the jejunum and the duodenum, and finally in the stomach. The reappearance time of the phase III contractions in the stomach was 105.8 +/- 10.6 h (n = 4). In the early post-operative period, KW-5139 (0.5 microgram kg-1, i.v.) induced phase-III-like contractions, whereas PGF2 alpha (50 micrograms kg-1, i.v.) induced simultaneously occurring contractions over the whole gastrointestine. The treatment with KW-5139 (0.5 microgram kg-1, i.v.) four times (twice daily on the first and the second post-operative day) significantly (P < 0.05) shortened the time required to recover the phase III contractions in the stomach (64.2 +/- 2.2 h, n = 4), whereas that with PGF2 alpha (50 micrograms kg-1, i.v.) four times did not (111.3 +/- 17.2 h, n = 4). The present results indicate that, after laparotomy, the cyclical motor activity recovers faster in the distal intestine than in the proximal intestine and the stomach, and that KW-5139, but not PGF2 alpha, shortens the reappearance time of the phase III activity in the stomach.

Analysis of Variance↗

PubMed1995

Binding and functional characterization of alpha-2 adrenoceptors in isolated swine myometrium.

1. Alpha-adrenoceptors in the uterus of cyclic mature pigs were investigated for their binding characteristics as shown by a radioligand study employing [3H]-prazosin and [3H]-rauwolscine, and the alpha-adrenoceptors were studied for their functional roles on motility as shown mechanically in vitro. 2. Noradrenaline (10 nM-1 microM) caused a tetrodotoxin-resistant contraction in the cornual longitudinal muscle. The response was decreased by yohimbine (10 nM-1 microM) but not by prazosin (1 microM). 3. Clonidine, xylazine, phenylephrine and methoxamine also elicited a concentration-dependent contraction of the cornual longitudinal muscle. The ranking according to the potency was clonidine > xylazine >> phenylephrine > or = methoxamine. On the other hand, these alpha-adrenoceptor agonists did not elicit contraction of the cornual circular muscle even at 100 microM. 4. Noradrenergic contraction induced by transmural stimulation was significantly decreased by yohimbine (10-100 nM) but not by prazosin (1 microM). 5. The swine myometrium contained both alpha-1 (13%) and alpha-2 (87%) adrenoceptors. The distribution of alpha-adrenoceptors was muscle layer-specific, i.e. the number of both types of adrenoceptors in the longitudinal muscle was four times higher than that in the circular muscle. 6. These results show that although swine myometrium contains both alpha-1 and alpha-2 adrenoceptors, the alpha-2 type is predominant and largely responsible for mediating the excitatory response to both exogenous and endogenous noradrenaline in the cornual longitudinal muscle.

Adrenergic alpha-1 Receptor Agonists↗

PubMed1994

Correlation between high temperature dependence of smooth muscle myosin light chain phosphatase activity and muscle relaxation rate.

Q10 values of the protein phosphatases that can dephosphorylate the regulatory light chain of smooth muscle myosin were determined. Six phosphatases were examined, i.e. skeletal muscle protein phosphatase 1c; protein phosphatase 2Ac; smooth muscle phosphatases (SMP) I, II, and IV; and myosin-associated protein phosphatase (MAP phosphatase). Among them, SMP-IV and MAP phosphatase, which can dephosphorylate intact smooth muscle myosin, showed extremely high Q10 values (5.3 and 5.2, respectively). On the other hand, the Q10 values of other tested phosphatases were within the range of the normal enzyme reaction (Q10 = 2.0). The rate of dephosphorylation of the myosin light chain in alpha-toxin-skinned strips was measured at different temperatures. The results provided a Q10 of 5.1, which was quite similar to those values obtained for SMP-IV and MAP phosphatase. These results suggest that the physiological myosin light chain phosphatases are SMP-IV and/or MAP phosphatase, i.e. type 1 protein phosphatases. The temperature dependence of maximum force, the steady-state extent of myosin light chain phosphorylation, and the relaxation rate of alpha-toxin-permeabilized rabbit portal vein smooth muscle strips were measured. Both maximum force and the extent of myosin light chain phosphorylation were significantly higher at lower temperature (15 degrees C) than at higher temperature (25 degrees C) under all pCa conditions tested, i.e. > 8, 6.3, and 5. The temperature dependence of the relaxation rate was much steeper (decreased 4 times by lowering the temperature from 25 to 15 degrees C) than that of the initial rate of increase in force development (decreased 1.4 times by lowering the temperature from 25 to 15 degrees C). These results are consistent with the Q10 values of myosin light chain phosphatases (Q10 = 5) and myosin light chain kinase (Q10 = 1.7) and further show that the smooth muscle type 1 phosphatases are responsible for the dephosphorylation of smooth muscle myosin in situ.

Animals↗

PubMed1994

2-Hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine induction of recombinational mutations in mammalian cell lines as detected by DNA fingerprinting.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant mutagenic heterocyclic amine in cooked foods. Two mouse tumor cell lines, BMT11 and FM3A, were exposed to its proximate form, 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP). Fifty-six subclones of BMT11 and 39 subclones of FM3A were isolated and analyzed by DNA fingerprinting. Treatment with 10-20 microM N-OH-PhIP gave rise to extra bands or shifted bands, but treatment without N-OH-PhIP did not. This suggests that mutations resulting from recombination were induced. The mutation frequencies were 21-53% and 22-35% for BMT11 and FM3A, respectively. These findings suggest that PhIP induces recombinational mutations.

Animals↗

PubMed1994

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--II.

In a previous paper, we reported that a novel ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. In order to obtain more potent gastrointestinal motility enhancing agents than compound 2 and to examine the effects of various substituents both at a nitrogen atom (B) in the 2-imidazolidinylidene propanedinitrile moiety and a basic nitrogen atom (C), compounds 5-29 were synthesized and evaluated for acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically stimulated contractions of guinea pig ileum. Introduction of alkyl, benzyl, aryl or acyl groups to the nitrogen (B) or (C), remarkably influenced both activities. Among these, compounds 14 and 15 showed more potent AChE inhibitory activity (IC50 = 6.7, 6.8 nM, respectively) than compound 2 and were active in potentiating action on the ileal contraction (EC30 = 9.5, 11 nM, respectively) together with a negligible histamine H2-receptor blocking property. Furthermore, these compounds were found to be more effective in the enhancement of gastrointestinal motility in anesthetized rabbits than compound 2.

Animals↗

PubMed1994

A novel mechanism for the Ca(2+)-sensitizing effect of protein kinase C on vascular smooth muscle: inhibition of myosin light chain phosphatase.

Mechanisms of Ca2+ sensitization of both myosin light chain (MLC) phosphorylation and force development by protein kinase C (PKC) were studied in permeabilized tonic smooth muscle obtained from the rabbit femoral artery. For comparison, the Ca2+ sensitizing effect of guanosine 5'-O-(gamma-thiotriphosphate) (GTP gamma S) was examined, which had been previously shown to inhibit MLC phosphatase in phasic vascular smooth muscle. We now report that PKC activators (phorbol esters, short chain synthetic diacylglycerols and a diacylglycerol kinase inhibitor) and GTP gamma S significantly increase both MLC phosphorylation and force development at constant [Ca2+]. Major phosphorylation site occurring in the presence of phorbol-12,13-dibutyrate (PDBu) or GTP gamma S at constant [Ca2+] is the same serine residue (Ser-19) as that phosphorylated by MLC kinase in response to increased Ca2+ concentrations. In an ATP- and Ca(2+)-free solution containing 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), to avoid the kinase activity, both PDBu and GTP gamma S significantly decreased the rate of MLC dephosphorylation to half its control value. However, PDBu inhibited the relaxation rate more than did GTP gamma S. In the presence of microcystin-LR to inhibit the phosphatase activity, neither PDBu nor GTP gamma S affected MLC phosphorylation and force development. These results indicate that PKC, like activation of GTP binding protein, increases Ca2+ sensitivity of both MLC phosphorylation and force production through inhibition of MLC phosphatase.

Animals↗

PubMed1994

Muscle layer and regional differences in autonomic innervation and responsiveness to transmitter agents in swine myometrium.

1. To clarify possible regional and muscle layer differences in adrenergic innervation of swine myometrium, functional, biochemical and histochemical experiments were performed on longitudinal (LM) and circular (CM) muscle isolated from non-pregnant uteri of 84 gilts. 2. Transmural stimulation (TMS) in the presence of propranolol evoked tetrodotoxin-sensitive contractions in a frequency-dependent manner (2-20 Hz) in LM and CM. The cornual LM contractions were attenuated by phentolamine (1 microM) and by guanethidine (10 microM) though unaffected by atropine (1 microM). Contractions in cervical LM were diminished by atropine but not by phentolamine, and the corpus LM contractions were reduced incrementally by atropine and phentolamine when added sequentially. In CM, the TMS-induced contractions were abolished by tetrodotoxin and atropine in all three regions. 3. In response to noradrenaline (NA) and acetylcholine (ACh), LM contractile intensity was the most potent in cornua, slightly weaker in the corpus and weakest in the cervix. CM was insensitive to NA, and contractile responses elicited by ACh indicated no regional variation. 4. NA content, significantly greater in LM than in CM, was most highly concentrated in cornual LM. Nerves exhibiting glyoxylic acid-induced histofluorescence occurred in both LM and CM, though more abundantly in LM and with notable density in the cornual LM. Cholinesterase activity, distributed evenly throughout the three myometrial regions studied, was more intense in LM than in CM. 5. These results show that, in swine myometrium, innervation in cornual LM is predominantly noradrenergic, cervical LM is mostly cholinergic, and throughout the myometrium the CM layers are principally cholinergic.

Acetylcholine↗