Isometric tension was measured to investigate the effects of guanosine-5''-triphosphate (GTP) on the run-down of myofilament Ca²⁺ sensitivity in isolated rat mesenteric arteries permeabilized with β-escin. The Ca²⁺ sensitivity assessed by the EC₅₀ value for the Ca²⁺ (0.1-100μM)-tension relationship progressively runs down in the control strips, while it was well-preserved for 5-successive Ca²⁺ applications in the presence of GTP (50 μM); no significant difference was found in the Ca²⁺ sensitivity observed with the 1st Ca²⁺ application between the control and GTP-treated strips. Guano sine-5''-(2-Ο-thio) diphosphate (GDPβS, 100 μM) significantly decreased the Ca²⁺ sensitivity with the 1st Ca²⁺ application and eliminated the run-down of Ca²⁺ sensitivity. GTP (3 -150 μM), applied to the strips submaximally precontracted with Ca²⁺, had a little effect on the Ca²⁺ contractions in the early stage of experiments, but dramatically enhanced the Ca ²⁺ contractions in their later stage; its latter effect was mimicked by guanosine-5''-(3-Ο-thio) triphosphate (GTPγS) and reversed by GDP13S (100 μM). The results suggest: 1) loss of endogenous GTP following permeabilization is involved in the run-down of Ca²⁺ sensitivity; and 2) activation of G-proteins is involved in Ca²⁺-activation of contractile proteins.

View full abstract

Fifteen children (mean age ±SD: 6.4±3.4, range: 2-12 years) with an acute asthma attack were treated by an intravenous dosage regimen of theophylline (30 min loading infusion of 6 mg/kg body weight followed by a constant infusion of 1 mg/kg, twice for 6 hr each). Three blood samples were drawn (each 15 min after the bolus infusion and after the two infusion periods of 6 hr). Plasma clearance (CL), apparent volume of distribution (Vd) and elimination half-life (t_1/2) were estimated by the Bayesian approach using either only the first peak level (Bay 1) or all three monitored concentrations (Bay 3). These values were compared to the parameters calculated by a standard pharmacokinetic procedure (SC). Therapeutic steady state plasma levels around 12 μg/ml were rapidly achieved, and the pharmacokinetic parameters (CL =1.1-1.5 ml/min/kg, Vd = 0.44 0.501/kg, t_1/2 = 3.5 5.4 hr) differed slightly between the 3 methods applied. There was a significant linear correlation between the Bayesian-derived and SCderived pharmacokinetic parameters. However the method Bay 1 seems to overestimate the elimination rate of theophylline more than Bay 3 does. In conclusion, Bayesian-based therapeutic plasma level monitoring (Bay 3 are better than Bay 1) can be utilized for individualized pharmacokinetic calculations and proper dosage predictions of theophylline in pediatric patients.

View full abstract

We have established models of cell damage induced by acid and pepsin using rat gastric epithelial cells (RGMI). In the present study, the effects of aluminum hydroxide [AI(OH)₃] and potassium sucrose octasulfate (KSOS), which are components of sucralfate, and sucralfate on cell damage and peptic activity of pepsin were examined. Pretreatment of cells with sucralfate (0.1-3 mg/ml) or Al(OH)₃ (0.1-1 mg/ml) for 2 hr prevented both acid (pH 4.0) and pepsin (pH 4.5) induced cell damage. However, KSOS (0.1-1 mg/ml) did not show any effects on two different types of cell damage. The peptic activity of pepsin at pH 4.5 was about 10010 of that at pH 2.0. Sucralfate and KSOS slightly inhibited peptic activity at pH 4.5. Al(OH)₃ inhibited peptic activity by approximately 50010; however, no concentration-dependent pattern was observed. Pepstatin (0.003-0.1 mg/ml), a specific inhibitor of pepsin, inhibited the peptic activity in a concentration-dependent manner. Here, we confirmed that sucralfate and Al(OH)3 have cytoprotective effects against acid and pepsin-induced cell damage. The mechanism behind the cytoprotective effects of sucralfate seems to relate to adhesion of the cell surface and neutralization of hydrogen ion by aluminum that prevents the penetration of hydrogen ions into the cells.

View full abstract

We examined the effects of cilnidipine, which is an L and N-type Ca²⁺ channel blocker, on adrenergically regulated renal functions in anesthetized dogs. Renal nerve stimulation (RNS) at high frequency (3-7 Hz) decreased renal blood flow (RBF) without changes in systemic blood pressure. The RBF response was inhibited by intrarenal arterial (i.r.a.) infusion of cilnidipine at 0.1-0.3 μg/kg/min. Lowfrequency RNS (0.5 -1 Hz) reduced absolute and fractional urinary sodium excretion. These responses were attenuated during i.r.a. infusion of cilnidipine at 0.3 μg/kg/min. An increase in norepinephrine secretion rate induced by low-frequency RNS was also attenuated during cilnidipine infusion. These results suggest that cilnidipine can suppress norepinephrine release from the renal nerve endings and thereby interfere with the neural control of renal functions.

View full abstract

In Chinese hamster ovary cells stably expressing the cloned human cholecystokinin (CCK)_B /gastrin receptor, cholecystokinin octapeptide (CCK-8) evoked increases in [Ca²⁺]_i monitored by digitized video imaging of fura-2 fluorescence ratios. At concentrations around 10 pM, CCK-8 elicited [Ca²⁺]_i oscillations, which were blocked by elimination of extracellular Ca²⁺, by a phospholipase C inhibitor, U-73122, by a protein kinase C inhibitor, H7, as well as by phospholipase A2 (PLA₂) inhibitors, ONO-RS-082 and aristolochic acid. At higher concentrations, CCK-8 induced a single biphasic [Ca²⁺]_i rise consisting of a large peak followed by a lower sustained plateau, while the response turned into [Ca²⁺]_i oscillation when the extracellular Ca²⁺ was eliminated or a PLA₂ inhibitor was included. CCK-8 stimulated the release of arachidonic acid, and this was inhibited by aristolochic acid. Arachidonic acid caused an increase in [Ca²⁺]_i which was dependent upon extracellular Ca²⁺. These results suggest that the activation of PLA₂ might be involved, at least in part, in the Ca²⁺ influx that maintains the sustained plateau phase of [Ca²⁺]_i as well as the [Ca²⁺]_i oscillation when CCK_B receptors are stimulated.

View full abstract

We studied the central nervous system (CNS) effects of HSR-609 (3-[4-(8-fluoro-5, 11-dihydrobenz[b]oxepino[4, 3-b]pyridin-11-ylidene)piperidino]propionic acid dihydrate), a novel amphoteric antiallergic agent having antihistaminic activity. Its effects on the behavior of mice and the electroencephalograms (EEG) of unanesthetized and unrestrained rabbits after oral administration were compared with those of typical antiallergic agents and the non-amphoteric basic compound PY-608 (8-fluoro-5, 11-dihydro-l1-(1-methyl-4-piperidylidene)benz[b]oxepino[4, 3-b]pyridine), which has a chemical structure similar to that of HSR-609. HSR-609 (3-300 mg/kg) had no effect on general behavior, spontaneous locomotor activity, hexobarbital-induced sleeping time and reserpine-induced hypothermia in mice. HSR-609 (10-100 mg/kg) and terfenadine (100 mg/kg) had no effect on spontaneous EEG, sleep-wakefulness cycles and EEG power spectra in rabbits. On the other hand, cyproheptadine (3-30 mg/kg), ketotifen (30-100 mg/kg) and PY-608 (0.3 -100 mg/kg) caused increases and/or decreases of spontaneous locomotor activity, prolongation of hexobarbital-induced sleeping time and antagonistic effects on reserpine-induced hypothermia in mice. These agents (30 mg/kg) increased slow wave sleep and enhanced EEG power spectra at low frequency bands such as δ and θ in rabbits. These findings suggest that HSR-609 has no inhibitory effect on the CNS due to its amphoteric chemical structure.

View full abstract

We investigated whether angiotensin II was involved with diabetic nephropathy in the mouse model. Twelve days after streptozotocin (STZ) injection, the urinary albumin excretion (UAE) level was increased by 118% of the baseline value. On days 21, 28, 35 and 42 after STZ injection, the UAE levels were significantly increased compared with the level at day 12. A marked elevation of creatinine clearance and diabetic-induced renal hypertrophy were also observed on day 49 after STZ injection. The 35-day treatments of captopril and Dup 753 (angiotensin II type 1 receptor antagonist) significantly attenuated the increment of UAE levels (26.4% on dayl4 and 34.6% on day 28). PD123177 (angiotensin II type 2 receptor antagonist) also attenuated the increment of UAE (24.7% on dayl4) at the dose of 150 mg/kg. Furthermore, Dup 753 partially prevented diabetic-induced renal hypertrophy. These results suggest that angiotensin II type 2 receptor as well as type 1 receptor may be involved in the development of diabetic nephropathy in the STZ-induced diabetic mice, and these mice are beneficial models of early diabetic nephropathy.

View full abstract

To develop a model of chronic experimental asthma in guinea pigs, the animal was forced to inhale the mist of a low dose of ovalbumin (OA) adsorbed on fine Al (OH) ₃ for sensitization once every 4 weeks. The animal was challenged by inhalation with the mist of OA on day 14 after the respective sensitizations. Either the first or the second antigen challenge markedly induced an early asthmatic response (EAR), whereas there was hardly any late asthmatic response (LAR). At the 3rd challenge, LAR also emerged with some severity. These dual responses were consistently observed until the 10th challenge. On the other hand, repeated inhalation/challenge, once every 2 weeks, with OA alone at the same dose tended to lead to the desensitization of the EAR. In addition, LAR was hardly observed throughout the experiments. In both groups, γ₁ and IgE levels in the serum were elevated by the repetitive antigen inhalations, yet no obvious relationship between these antibody levels and the intensity of either EAR or LAR was recognized. The present results indicate that the asthmatic model with reproducible EAR and LAR developed in this study appears to be very beneficial for the investigation of bronchial asthma and for the assessment of anti-asthma drugs.

View full abstract

The effects of various selective phosphodiesterase (PDE) inhibitors on muscle contractility in guinea pig ileal longitudinal smooth muscle were investigated. 1) 3-Isobutyl-l-methyl xanthine (IBMX) or zaprinast markedly inhibited the high K⁺ or carbachol (CCh)-induced contraction and increased cGMP content of the muscle strip in a concentration-dependent manner. However, these agents only slightly increased the cAMP content. Milrinone or Ro20-1724 also slightly inhibited the high K⁺ or CCh-induced contraction and increased the cAMP content, but did not increase cGMP. 2) In a fura2-loaded muscle, IBMX or zaprinast inhibited both contractions and the increase in intracellular Ca²⁺ ([Ca²⁺]_i) level induced by high K⁺ or CCh, although the inhibitory effect on the [Ca²⁺]i level was smaller than that on muscle tension. 3) In α-toxin-permeabilized muscles, cGMP, IBMX or zaprinast significantly inhibited the Ca²⁺induced contraction. These results suggest that IBMX and zaprinast inhibit muscle contraction in the ileal longitudinal smooth muscles mainly through an increase in cGMP and the inhibitory mechanism of IBMX or zaprinast is involved in the decreases in the [Ca²⁺]_i level and sensitivity of contractile elements to Ca²⁺.

View full abstract

Although modulation of hippocampal synaptic plasticity by neurotrophins or growth factors has recently become an extensively investigated subject, there are no reports arguing for the contribution of the transforming growth factor (TGF)-β superfamily. In the present study, we examined the effect of activin, a member of the TGF-β superfamily, on long-term potentiation (LTP) of the dentate gyrus in anesthetized rats. Activin significantly impaired the formation of LTP induced by tetanic stimulation (60 Hz for 0.27 sec), but not that by strong tetanic stimulation (60 Hz for 0.5 sec). These results suggest that activin selectively blocks the induction of LTP evoked by threshold tetanic stimulation.

View full abstract

A selective inhibitor of cyclic nucleotide phosphodiesterase (PDE) 4, rolipram, markedly enhanced the forskolin-induced increase of intracellular dopamine and dihydroxyphenylacetate (DOPAC, a metabolite of dopamine) levels in primary cultured rat mesencephalic neurons and the forskolin-induced increase of dopamine and DOPAC in extracellular medium. Selective inhibitors of PDE2, PDE3, PDE5 and PDE6 did not have such a promoting effect, and the PDE1 inhibitor vinpocetine and W-7 caused dopamine depletion in the neurons. These findings suggested that PDE4 plays a major role in regulating the intracellular cAMP level to control the dopamine biosynthesis in mesencephalic neurons, whereas PDE 1 regulates dopamine release instead.

View full abstract

Superoxide anion (0₂^-) acts as an exacerbation factor in interstitial pneumonia. Lecithinized-superoxide dismutase (PC-SOD), which is synthesized with a lecithin derivative bound covalently to recombinant human Cu, Zn-SOD, has a longer half-life in plasma and higher affinity to cell membranes than unmodified SOD. The effect of PC-SOD was evaluated using the bleomycin-induced interstitial pneumonia mouse model. Treatment with PC-SOD at 10 mg/kg significantly reduced the hydroxyproline content and fibrosis score. Namely, PC-SOD suppressed the progression of pulmonary fibrosis on the bleomycin-induced interstitial pneumonia mouse model. PC-SOD may be a potential drug for interstitial pneumonia therapy.

View full abstract

The effect on the in vitro withdrawal sign induced by naloxone in morphine-dependent guinea pig ileum has been analyzed. Salmon calcitonin (s-CT) dose-dependently reduced the force of the contraction induced by naloxone in morphine incubated tissues, but did not modify the contraction induced by administration of acetylcholine or substance P in non-treated tissues. Therefore, the effect of s-CT in morphine incubated tissues may not be attributable to postsynaptic mechanisms, and an inhibitory modulation of the excitatory pathways triggered by naloxone would be suggested. In conclusion, s-CT is able to prevent the withdrawal sign in vitro.

View full abstract