The mechanism of the vasodilatory effect of 5-methyl-6-(4-pyridyl)-2H-1, 4-thiazin-3 (4H)-one (ZSY-27), a non-catecholamine and non-glycoside positive inotropic agent with a vasodilatory action, was investigated using helically-cut strips of the rabbit thoracic aorta. The contractile responses of the thoracic aorta to phenylephrine and prostaglandin F_2α were antagonized noncompetitively in a concentration-dependent manner by ZSY-27 (1×10^-4-1×10^-3M). Furthermore, precontractions induced by high K (34.5 mM K) and by phenylephrine (1×10^-6M) were relaxed in a concentrationdependent manner by ZSY-27 (1×10^-6-1×10^-3M). These relaxant effects were not affected by a decrease in extracellular Ca or by pretreatment with methylene blue, an inhibitor of guanylate cyclase, but were significantly potentiated by pretreatment with forskolin, a direct stimulator of adenylate cyclase. Moreover, the amount of Ca stored in smooth muscle cells was estimated from the amplitude of the phasic contractions induced by phenylephrine in Ca-deprived medium. The first phasic contraction induced by phenylephrine was inhibited by pretreatment with ZSY-27. After ZSY-27 was washed out with a Ca-deprived solution, the seconed phasic contraction induced by phenylephrine occurred manifestly, but not in preparations untreated with ZSY-27. It is concluded that ZSY-27 caused a nonspecific relaxation of arterial smooth muscle contractility mainly by acting on some processes distal to adenosine 3', 5'-monophosphate (cAMP) production by adenylate cyclase ; probably inhibition of cAMP-phosphodiesterases.

View full abstract

The aim of this investigation was to substantiate the hypothesis that the vasorelaxant effects of 5-methyl-6-(4-pyridyl)-2H-1, 4-thiazin-3 (4H)-one (ZSY-27) are mediated by accumulation of intracellular cyclic nucleotides as a consequence of inhibition of cyclic nucleotide phosphodiesterase activity. Both activities of adenosine 3', 5'-monophosphate-phosphodiesterase (cAMP-PDE) in the presence of ethylene glycol-bis (β-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) and guanosine 3', 5'-monophosphate-phosphodiesterase (cGMP-PDE) in the presence of calcium-calmodulin from rabbit thoracic aorta were inhibited in a concentration-dependent manner by ZSY-27 (10^-5-10^-3M). The IC₅₀ values for ZSY-27 on cAMP-and cGMP-PDE activity were 2.1×10^-4 and 8.8×10^-4M, respectively. Furthermore, ZSY-27 antagonized competitively cAMP-PDE (K_i=1.9×10^-4M). On the other hand, ZSY-27 exhibited a mixed-type inhibitory pattern, with reduction of both maximum velocity and affinity for the substrate of the cGMP-PDE, with a K_i value of 1.0×10^-3M. Spontaneous myogenic tone of rabbit thoracic aorta was significantly attenuated from 1 min after addition of ZSY-27 (3×10^-4M). Contents of cAMP and cGMP were significantly increased from 1 and 3 min after addition of ZSY-27, respectively. Temporally, relaxant effects of ZSY-27 were associated with increases of cAMP content, but not with that of cGMP content. Furthermore, the relaxant effect of ZSY-27 on the phenylephrine-induced contraction was not affected by the pretreatment with nitroprusside. These results support the hypothesis that elevation of cAMP level via inhibition of cAMPPDE activity is intimately involved in the mechanism of vasorelaxation produced by ZSY-27.

View full abstract

The effects of 5-methyl-6-(4-pyridyl)-2H-1, 4-thiazin-3 (4H)-one (ZSY-27), a positive inotropic agent with a vasodilatory action, on a concentration-response curve of CaCl₂ in the KCl-depolarized rabbit thoracic aorta and Ca-uptake by the microsomal fraction from the rabbit artery were tested. ZSY-27 (10^-5-10^-4M) inhibited noncompetitively a concentration-response curve of CaCl₂ in the KCl-depolarized preparation. Furthermore, ZSY-27 (10^-5M) stimulated significantly Ca-uptake by the microsomal fraction in the presence of oxalate, as an indicator for Ca-uptake by the internal membrane, in every incubation time. However, it inhibited significantly that in the absence of oxalate, as an indicator for Ca-uptake by the plasma membrance-derived vesicle, after 6 min of incubation time. These results suggest that ZSY-27 stimulates Ca-uptake by the internal membranes and inhibits Ca-uptake by the plasma membrane-derived vesicles. Therefore, these effects of ZSY-27 are considered to be related to relaxation of vascular smooth muscle.

View full abstract

We have developed a method to control the effective time period of (1→3)-β-D-glucan in vivo by using (1→3)-β-D-glucanase and found that grifolan LE (GRN), a (1→3)-β-D-glucan, administered intraperitoneally to the host required more than 2 d to exert antitumor activity. During these two days many immunological changes were induced, such as increasing the number of peritoneal exudated cells (PEC), augmentation of production of interleukin 1 (IL-1), acid phosphatase and phagocytic capacity of adherent cells in PEC. In addition, there was increased carbon clearance activity in vivo, augmentation of responsiveness of splenocytes to mitogens such as concanavalin A and lipopolysaccharide (LPS) and production of ceruloplasmin. When (1→3)-β-D-glucanase was injected 1 d after GRN administration, IL-1 productivity and responsiveness to LPS were significantly reduced, but lysosomal enzyme activity and phagocytosis of macrophage and production of ceruloplasmin were similar to those not treated with glucanase. These facts indicate that the induction of the activities of the former group requires longer contact of host cells with the glucan, and the latter group requires a shorter period to achieve fully active stages.

View full abstract

The behavioral and electroencephalographic (EEG) effects of intramuscular fluphenazine decanoate (Fl-D) were investigated in rats and compared with those of fluphenazine enanthate (Fl-E) and fluphenazine HCl (Fl-HCl). It was clearly observed that 1) these two depot type neuroleptics reduced open-field activity, 2) antagonized methamphetamine-induced hyperactivity, 3) inhibited the conditioned avoidance response, and 4) produced catalepsy, for a substantially long period of time (4-35 d). Although both Fl-D and Fl-E significantly inhibited muricide in olfactory bulbectomized rats and impaired rotarod performance, these effects were relatively weak in potency and short-lasting (4 h-2 d). The EEG was changed to a drowsy pattern which consisted of high voltage slow waves following the injection of Fl-D and Fl-E. Fl-D significantly inhibited the EEG arousal response to auditory stimulation, but Fl-E did not. However, neither Fl-D nor Fl-E inhibited the EEG arousal response to electrical stimulation of the midbrain reticular formation and posterior hypothalamus. These results indicate that Fl-D has the same spectrum of pharmacological activity as Fl-E, except for its longer duration of action in antagonizing methamphetamine as well as in inhibiting the EEG arousal response to auditory stimulation.

View full abstract

Guinea pig peritoneal macrophages generate superoxide anion (O^-₂), when stimulated with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), phorbol-myristate acetate (PMA) or ovalbumin complex of guinea pig IgG2 antibody (OAγ₂). These responses were found to be inhibited by a Chinese traditional medicine, Juzentaihoto (JT). When the inhibition was assayed by the use of fMLP as a stimulant, at least one of the substances responsible for the inhibitory activity of JT was identified to be cinnamic acid. An authentic sample of cinnamic acid also inhibited the O^-₂ generation by fMLP-stimulated macrophages. Cinnamic acid, however, did not inhibit the O^-₂ generation, when macrophages were stimulated with PMA and OAγ₂. These results indicate that a certain cinnamic acid-inhibitable factor may be involved in the intracellular triggering event (s) initiated by fMLP, leading to activation of the respiratory burst reduced nicotinamide adenine dinucleotide phosphate oxidase, but not in those by PMA and OAγ₂.

View full abstract

The influence of alloxan-induced diabetes on the adrenergic constriction of the rat cerebral vasculature was investigated in the in situ perfused brain preparation. The preparation was perfused with an artificial medium at a constant flow rate and the change in perfusion pressure was measured. Norepinephrine (NE) and serotonin produced a dose-dependent increase in the perfusion pressure, but only the effect of NE was significantly enhanced in the diabetic rats. Such an enhancement of NE-induced vasoconstriction was not observed in the perfused hindquarter preparations from the diabetic rats. Propranolol (1 μM) potentiated the cerebrovascular constriction by NE and abolished the difference between diabetic and control rats at low doses of NE. However, vasoconstriction by the higher doses of NE in the diabetic rats was still enhanced even in the presence of propranolol. The cerebrovascular constriction by phenylephrine was also enhanced in the diabetic rats, while the vasoconstricting effects of clonidine, xylazine and oxymetazoline were not affected by diabetes. These results suggest that the enhanced cerebrovascular constriction by NE may be due to either the reduced response through β-adrenoceptors or the enhanced response through α₁-adrenoceptors. The enhanced adrenergic constriction of the cerebral vasculature might be concerned with the high incidence of neurological deficit in stroke patients with diabetes.

View full abstract

The present investigation was undertaken to clarify the in vitro effect of synthetic [Asu^1.7] eel calcitonin (CT) on bone metabolism in tissue culture. Calvaria were removed from weanling rats (3-week-old male) and cultured for periods up to 96 h in Dulbecco's Modified Eagle Medium supplemented with antibiotics and bovine serum albumin. The experimental cultures contained 1.0 to 100 ng/ml CT. All cultures were incubated at 37°C in 5% CO₂-95% air. Bone calcium content was increased significantly by the presence of 10 and 100 ng/ml CT. This increase was blocked by the presence of 10^-6M cycloheximide or 10^-7M actinomycin D. Bone alkaline phosphatase activity was significantly increased by the presence of 100 ng/ml CT for 48 and 96 h. Bone acid phosphatase activity was not altered significantly by CT (1-100 ng/ml). The incorporation of [³H] proline into the acidinsoluble residues of bone tissue was significantly increased by the presence of CT (1-100 ng/ml) for 96 h. This increase was completely blocked by the presence of 10^-7 M cycloheximide. Bone DNA content was significantly raised by the presence of 10 and 100 ng/ml CT for 96 h. Furthermore, the culture with CT (10 and 100 ng/ml) produced a significant decrease in glucose concentration in the medium. Also, CT (10 and 100 ng/ml) stimulated the production of pyruvic acid from bone tissue. These results suggest that CT had a direct stimulatory effect on bone formation and mineralization in vitro, and that the hormone stimulates energy metabolism in bone cells.

View full abstract