Tetsuo Ohashi

Potent inhibition of spontaneous rhythmic contraction by a novel β2-adrenoceptor agonist, HSR-81, in pregnant rat uterus

We examined the effect of HSR-81 ((-)-(R)-alpha-[(tert-butylamino)methyl]-2-chloro-4-hydroxybenzyl alcohol L-tartrate), a newly developed, potent and selective beta 2-adrenoceptor agonist, as well as ritodrine and isoproterenol, on the spontaneous rhythmic contraction in uteri isolated from late pregnant, middle pregnant and non-pregnant (dioestrous and oestrous) rats. The three agonists inhibited the spontaneous rhythmic contraction at all the stages in a concentration-dependent manner. The pD2 value for HSR-81 was greater in late pregnancy than in dioestrus and oestrus. In the uterine preparations of late pregnancy and dioestrus, ICI-118,551 (1-(7-methylindan-4-yloxy)-3-isopropyl-aminobutan-2-ol , a selective beta 2-adrenoceptor antagonist) and atenolol (a selective beta 1-adrenoceptor antagonist) produced a parallel rightward shift of the concentration-response curves for HSR-81. The pKB values for ICI-118,551 and atenolol suggest that the inhibitory effect of HSR-81 was mediated through beta 2-adrenoceptors in the two stages. In the membranes prepared from rat uteri in late pregnancy and dioestrus, the equilibrium dissociation constant for [125I]iodocyanopindolol binding was not significantly different between the two stages. The three beta-adrenoceptor agonists and the two antagonists competed for the specific [125I]iodocyanopindolol binding and the pKi values were not significantly different between the two stages. However, the maximum number of binding sites was significantly greater in late pregnancy than in dioestrus. The configuration of the competition curves and the pKi values for the two antagonists confirmed the fact that these membranes contain predominantly beta 2-adrenoceptor subtype. These results indicate that the potent inhibition of the spontaneous rhythmic contraction by HSR-81 in the pregnant uterus may be due to the increased number of beta 2-adrenoceptors.

Effects of RS-601, a Novel Leukotriene D4/Thromboxane A2 Dual Receptor Antagonist, on Asthmatic Responses in Guinea Pigs

The effects of 4-[4-[5,5,6,6,6-pentafluoro-1-(4-fluorobenzene-sulfonamido)hexyl]phenyl]butyric acid (RS-601), a novel leukotriene D4 (LTD4)/thromboxane A2 (TxA2) dual receptor antagonist, on bronchial asthmatic responses in guinea pigs were examined. The effects were compared with those of pranlukast (LTD4 receptor antagonist) and S-1452 (TxA2 receptor antagonist). RS-601 inhibited the increase in airway resistance caused by LTD4 and TxA2 mimetic compound, U-46619, but not by histamine. RS-601 and pranlukast but not S-1452 inhibited an antigen-induced late asthmatic response. In addition, RS-601 inhibited an antigen-induced airway hyperresponsiveness (AHR), whereas pranlukast and S-1452 had no effect on the AHR. The antigen-induced increase in inflammatory cells in airway was not affected by all examined agents. Furthermore, bacterial lipopolysaccharide-induced AHR in guinea pigs was clearly suppressed by RS-601 but not by pranlukast and S-1452. The increase in airway inflammatory cells caused by lipopolysaccharide was not affected by all three drugs. These findings indicate that RS-601 has a potent antiasthmatic efficacy, especially on AHR, but does not affect accumulation of eosinophils in the airways.

医薬品の両性イオン化(第3報)1,2,3,4,10,14b-Hexahydrodibenzo-[c, f]pyrazino[1,2-α]azepine及び2,3,4,9-Tetrahydro-1H-dibenzo[3,4 : 6,7]cyclohepta[1,2-c]pyridineのN-Alkylcarboxylic Acid誘導体の合成とその薬理作用

The N-alkylcarboxylic acids of 1,2,3,4,10,14b-hexahydrodibenzo[c,f]pyrazino[1,2-alpha]az epi ne (6a) and 2,3,4,9-tetrahydro-1H-dibenzo[3,4: 6,7]cyclohepta[1,2- c]pyridine (6b) were synthesized and examined for pharmacological activities in vitro: an inhibitory effect on the monoamine [noradrenaline (NA) and 5-hydroxytryptamine (5-HT)] uptake into the rat crude synaptosome, an inhibitory effect on the 5-HT- and NA-induced contraction in the isolated rabbit aorta and on the histamine- and acetylcholine-induced contraction in the isolated guinea-pig ileum, and binding affinity for alpha 2-adrenoceptor and D2-receptor. The in vitro tests indicated that zwitter-ionization was capable of maintaining antihistaminic activity while greatly reducing other pharmacological activities such as effects on central nervous system. 3-[2,3,4,9-Tetrahydro-1H-dibenzo[3,4: 6,7]cyclohepta[1,2- c]pyridin-2-yl]propionic acid (6b-2), selected as a candidate antiallergic agent having equally potent activities in rats and guinea-pigs, exhibited strong inhibitory effects on 48 h homologous passive cutaneous anaphylaxis (PCA) in rats (ED50 = 0.012 mg/kg, p.o.) and on histamine-induced bronchoconstriction in anesthetized guinea-pigs (ED50 = 0.0088 mg/kg, p.o.).