Physical and functional interaction between BH3-only protein Hrk and mitochondrial pore-forming protein p32

Bcl-2 homology domain (BH) 3-only proteins of the proapoptotic Bcl-2 subfamily play a key role as initiators of mitochondria-dependent apoptosis. To date, at least 10 mammalian BH3-only proteins have been identified, and it is now being realized that they have different roles and mechanisms of regulation in the transduction of apoptotic signals to mitochondria. Hrk/DP5 is one of the mammalian BH3-only proteins implicated in a variety of physiological and pathological apoptosis, yet the molecular mechanism involved in Hrk-mediated apoptosis remains poorly understood. In an attempt to identify cellular proteins participating in Hrk-mediated apoptosis, we have conducted yeast two-hybrid screening for Hrk-interacting proteins and isolated p32, a mitochondrial protein that has been shown to form a channel consisting of its homotrimer. In vitro binding, co-immunoprecipitation, as well as immunocytochemical analyses verified specific interaction and colocalization of Hrk and p32, both of which depended on the presence of the highly conserved C-terminal region of p32. Importantly, Hrk-induced apoptosis was suppressed by the expression of p32 mutants lacking the N-terminal mitochondrial signal sequence (p32(74-282)) and the conserved C-terminal region (p32 (1-221)), which are expected to inhibit binding of Hrk competitively to the endogenous p32 protein and to disrupt the channel function of p32, respectively. Furthermore, small interfering RNA-mediated knockdown of p32 conferred protection against Hrk-induced apoptosis. Altogether, these results suggest that p32 may be a key molecule that links Hrk to mitochondria and is critically involved in the regulation of Hrk-mediated apoptosis.

Embolization of scalp AVF

We report scalp arteriovenous fistulas (AVFs) in which we performed embolization and examine the treatment method. The subjects were four cases of scalp AVF treated by embolization. All cases were male and three had a past history of scalp injury. As the feeding artery, we found a single artery in one case and multiple arteries in three cases. In three cases we employed a transarterial approach by cutting down the scalp and embolized the fistula with NBCA (N-butyl-cyanoacrylate). We conducted the embolization procedure as follows in order to securely occlude the fistula; 1) we obtained the precise location of fistula by the superselective angiography; 2) we induced the tip of microcatheter to immediately in front of fistula; 3) when high flow shunt was manifested, we controlled the flow by retaining the balloon catheter in the external carotid artery; 4) and injected NBCA by compressing around the fistula from above the scalp with a cylindrical instrument to prevent the migration of embolic material to the venous side. As a result, all cases were completely cured and there was no major complication except for transient postoperative pain. If the transfemoral approach to fistula is impossible, it is considered effective to cut down near the fistula and embolize the scalp AVF by direct puncture to the feeding artery with NBCA as embolic material.

The inhibitory effect of KT3-671, a nonpeptide angiotensin-receptor antagonist, on rabbit and rat isolate vascular smooth muscles: a possible involvement of K(ATP) channels

The vasoinhibitory effect of KT3-671, a recently synthesized nonpeptide angiotensin II (Ang II), AT1-receptor antagonist, and the factors affecting insurmountable antagonism of Ang II were examined in rabbit and rat isolated vascular smooth muscle preparations. In rabbit and rat aortic rings, KT3-671 caused insurmountable antagonism of Ang II. In addition, KT3-671 inhibited contractile responses to angiotensin III (Ang III). In rabbit isolated smooth muscles, KT3-671 was most effective in reducing the maximal contraction induced by Ang II in the renal artery followed by the basilar artery and the aorta. In rat renal arterial rings, KT3-671 (10(-5) M) inhibited the concentration-response curves of prostaglandin F2alpha and STA2. In rabbit and rat aortic rings without endothelium, the insurmountable antagonisms of Ang II by KT3-671 and EXP 3174 were changed to surmountable antagonism by pretreatment with DuP 753 and KT3-671, respectively. In addition, KT3-671 abolished the inhibitory effect of CV- 11974 in the rat aorta but not in the rabbit aorta. Indomethacin (10(-5) M) or the removal of endothelium did not affect the inhibitory effect of Ang II by CV-11974 or EXP 3174 but enhanced the insurmountable antagonism by KT3-671. ODQ (3 x 10(-6) M), N(G)-nitro-L-arginine (3 x 10(-4) M), 4-aminopyridine (3 x 10(-3) M), tetraethylammonium (TEA; 10(-3) M), or iberiotoxin (10(-7) M) did not affect the inhibitory action of KT3-671 or CV-11974. Methylene blue (3 x 10(-6) M), KCl (10(2) M), TEA (10(-2) M), or BaC12 (10(-4) M) changed the insurmountable antagonism by KT3-671 to surmountable antagonism and abolished the inhibitory effect of CV-11974. However, glibenclamide (3 x 10(-6) M) did not affect the inhibitory action of KT3-671 but reduced the insurmountable antagonism by CV- 11974. These results indicate that KT3-671 is an insurmountable antagonist of Ang II in the rabbit and rat aorta. The results in the rat aorta also suggest that K(ATP) channels may be involved in insurmountable antagonism of Ang II by KT3-671 and CV-11974. Key Words: KT3-671-Rabbit-Rat-Vascular smooth muscle-Angiotensin II-Insurmountable antagonist-K(TP)channels.

Morphological Study of Carotid Artery of WHHL Rabbit after Balloon Dilatation

SUMMARY

We performed balloon dilatation in the carotid artery of WHHL rabbits and examined subsequent morphological alteration over time. The balloon was inserted as far as the carotid bifurcation and observations were made on the morphological alteration after dilatation in the atherosclerotic intimal thickening from immediately after balloon dilatation over a period of ten months. Immediately after balloon dilatation, endothelial cells came of circularly and stretching, fragmentation off elastic fibers and coming off of smooth muscle cells of the media were confirmed. No change in the degree of thickening after dilatation was seen in the atherosclerotic intimal thickening of the carotid bifurcation. Three weeks later, endothelium covering except some parts, circular neointima and fibrosis of the media were observed; foamy cells had accumulated in the upper layer of the atherosclerotic intimal thickening, and that region was not yet covered with endothelial cells. The progress of fibrous intimal thickening so as to keep the lumen smooth was seen up to six months later, but foamy cells were not found in the neointima.

Antihypertensive activity and pharmacokinetics of KD3-671, a nonpeptide AT1-receptor antagonist, in renal hypertensive dogs

The antihypertensive activity and pharmacokinetics of KD3-671 (previously named KT3-671), a nonpeptide AT1-receptor antagonist, were investigated in renal hypertensive dogs with normal or high plasma renin activity (PRA). A single administration of KD3-671 at 3 and 10 mg/kg, p.o., to the hypertensive dogs with high PRA dose-dependently reduced mean blood pressure (MBP), which was not correlated with plasma KD3-671 concentration. Significant increases in PRA and plasma angiotensin (Ang) II occurred 2 h after KD3-671 dosing. Enalapril at 3 mg/kg, p.o., also reduced MBP. Neither KD3-671 nor enalapril affected heart rate. When given orally once a day for 29 days to the hypertensive dogs with normal PRA, KD3-671 at 3 and 10 mg/kg/day dose-dependently reduced MBP, which was smaller than that in the dogs with high PRA. This was the case for enalapril. The hypotension induced by the first dose of KD3-671 or enalapril was consistently observed after doses 8, 15, 22, and 29. After cessation of repeated dosing, no rebound phenomenon in MBP was observed. Pharmacokinetic parameters of KD3-671 were not influenced by repeated dosing. KD3-671 markedly increased both PRA and plasma Ang II concentration at 2 h after dosing. These results suggest that KD3-671 may be useful for the treatment of hypertension.

Therapeutic effect of egualen sodium (KT1-32), a new antiulcer agent, on chronic gastritis induced by sodium taurocholate in rats

We investigated the therapeutic effects of egualen sodium (KT1-32), a new antiulcer agent, on chronic erosive and atrophic gastritis induced by 5 months' administration of sodium taurocholate (TCA; 5 mM) in rats. The chronic gastritis was manifested by mucosal surface injuries (erosions), reduced mucosal thickness, reduction of the number of parietal cells, infiltration of inflammatory cells, and proliferation of collagenous fiber. Egualen sodium, (10-100 mg/kg, t.i.d.) administered orally to the rats for 2 weeks after the withdrawal of TCA, dose-dependently and significantly decreased the total length of erosions. The indicators of atrophic gastritis, i.e., reduced mucosal thickness and reduction in the number of parietal cells, were improved dose-dependently by the administration of this agent. Egualen sodium also reduced the inflammatory cell infiltration and the proliferation of collagenous fiber in the gastric mucosa in a dose-dependent manner. The reduced staining of neutral gastric mucus was improved by a high dose (100 mg/kg) of egualen sodium. The therapeutic effects of egualen sodium on experimental gastritis were superior to those of sofalcone and sodium guaiazulene 3-sulfonate. These results suggest that egualen sodium may be a promising agent for the treatment of erosive and atrophic gastritis.

Effect of repeated administration of KT3-671, a nonpeptide AT1 receptor antagonist, on diurnal variation in blood pressure, heart rate, and locomotor activity in stroke-prone spontaneously hypertensive rats as determined by radiotelemetry

KT3-671, a nonpeptide AT1 receptor antagonist, was administered to 20-week-old stroke-prone spontaneously hypertensive rats (SHRSP) daily for 3 weeks. Its effects on systolic, mean, and diastolic arterial blood pressure (SAP, MAP, DAP), heart rate and locomotor activity were investigated with radiotelemetry. A clear diurnal variation in blood pressure, heart rate, and locomotor activity was observed in synchrony with the light cycle. KT3-671 at a daily dose of 10 mg/kg orally (p.o), produced a significant and consistent reduction in blood pressure, preventing the development of hypertension. KT3-671 reduced SAP more than DAP, suggesting that it may affect both vascular tone and cardiac output. Although KT3-671 did not affect diurnal rhythms in heart rate and locomotor activity, it did cause a slight but significant reduction in heart rate. The MAP determined 23 h after the administration of KT3-671 showed a significant reduction from the day 2 of therapy to the day 3 after discontinuation of therapy, suggesting a long duration of antihypertensive action. There was no rebound increase in blood pressure after discontinuation of KT3-671 therapy. These results suggest that KT3-671 may be potentially useful in the therapy of hypertension.

Antihypertensive effect of chronic KT3-671, a structurally new nonpeptide angiotensin AT1-receptor antagonist, in stroke-prone spontaneously hypertensive rats

KT3-671 (2-propyl-8-oxo-1-[(2'-(1H-tetrazole-5-yl)biphenyl-4-yl)methyl]-4,5,6, 7-tetrahydrocycloheptimidazole), a structurally new nonpeptide angiotensin AT1-receptor antagonist, was administered orally and repeatedly to 15-week-old stroke-prone spontaneously hypertensive rats for 7 weeks; and its effects on blood pressure, heart rate, renal function, plasma renin concentration (PRC), plasma aldosterone concentration (PAC) and hypertension-related tissue damage in the brain, heart, kidney and mesenteric artery were investigated. KT3-671 at a dose of 3 or 10 mg/kg, p.o. per day prevented development of hypertension and produced a significant and consistent reduction of blood pressure in a dose-dependent manner. Enalapril at a dose of 10 mg/kg per day produced cardiovascular effects similar to those of KT3-671 at 10 mg/kg. Despite marked reduction in blood pressure, neither KT3-671 nor enalapril affected the heart rate. KT3-671 at 10 mg/kg produced a transient and significant reduction of urinary sodium excretion in the second week, but did not affect renal function at any other time during the experimental period. Both KT3-671 at 10 mg/kg and enalapril at 10 mg/kg produced a significant increase in PRC and showed a tendency to decrease PAC. Repeated administration of KT3-671 reduced the severity of the pathological changes in the kidney. These results suggest that KT3-671 is a potentially useful antihypertensive drug.

Pharmacological properties of KT3-671, a novel nonpeptide angiotensin II receptor antagonist

We examined pharmacological profiles of KT3-671, 2-propyl-8-oxo-1-[(2'-(1H-tetrazole-5-yl) biphenyl-4-yl)methyl]- 4,5,6,7-tetrahydro-cycloheptimidazole, a newly synthesized nonpeptide angiotensin II (AII) receptor antagonist in various in vitro and in vivo studies. KT3-671 displaced specific binding of [125I]Sar1 Ile8-AII to AT1 receptor with a Ki value of 0.71 +/- 0.14 x 10(-9) M in rat liver membranes, but had no affinity for AT2 receptor in bovine cerebellar membranes (Ki > 10(-5) M). In isolated rabbit aorta, KT3-671 produced a parallel rightward shift in the concentration-response curve for AII with a pA2 value of 10.04 +/- 0.12, but had no effect on KCl-, norepinephrine (NE)-, and serotonin (5-HT)-induced contractions. In conscious normotensive rats, KT3-671 (0.3-10 mg/kg, p.o.) inhibited the AII-induced pressor response dose dependently. In renal artery-ligated hypertensive rats, KT3-671 (0.1-3 mg/kg, p.o.) decreased arterial blood pressure (BP) dose dependently. The hypotensive action of 3 mg/kg KT3-671 was maintained for at least 24 h. These results suggest that KT3-671 is a potent AT1 subtype-selective and competitive nonpeptide AII receptor antagonist and has an orally active antihypertensive effect without agonistic activity.

Pharmacologic properties of KT2-962 (6-isopropyl-3-[4-(p- chlorobenzenesulfonylamino)-butyl]-azulene-1-sulfonic acid sodium salt); a new TXA2/prostaglandin endoperoxide receptor antagonist

Pharmacologic properties of KT2-962 (6-isopropyl-3-[4-(p-chlorobenzenesulfonylamino)butyl]-azulene+ ++-1-sulfonic acid sodium salt, KT) were studied in isolated rat aorta, rat tail artery, rabbit aorta, rabbit renal artery, and pig coronary artery. KT competitively inhibited the contractions induced by thromboxane A2 (TXA2) mimetic, U46619 (pA2 values 9.95, 8.85, 7.87, 8.49, and 9.12, respectively). KT also inhibited the contraction of rabbit aorta induced by prostaglandin2 alpha (PGF2 alpha, pA2 value 7.85) and the contraction of guinea pig ileum induced by LTD4 (pA2 value 5.48) but did not alter the contractions induced by norepinephrine (NE), Ca2+, serotonin, and histamine. KT did not alter the contractions of guinea pig ileum, which did not contract with U46619, induced by PGE2 and PGF2 alpha. KT inhibited the aggregations of rabbit platelets induced by U46619, arachidonic acid, and collagen (IC50 values 7.9, 140, and 16 microM, respectively) but not those induced by ADP. It also inhibited the specific binding of TXA2/PGH2 receptor antagonist, [3H]SQ29,548, to rabbit gel-filtered platelets with an IC50 value of 1.5 x 10(-8) M. In in vivo experiments with mice, oral administration of KT protected the U46619-induced sudden death with the minimum effective dose of 0.3 mg/kg and provided such protection for > 8 h at 1.0 mg/kg. These results indicate that KT is a new nonprostanoid type TXA2/PGH2 receptor antagonist that is orally effective and long acting.

[Healing promoting effect of azuletil sodium (KT1-32) on experimental chronic gastric ulcers and acceleration of healing in SPF environment]

We examined the healing promoting effects of azuletil sodium on acetic acid and clamping cortisone-induced gastric ulcer in rats. For the experiments on clamping-cortisone gastric ulcer, we used not only conventional rats in conventional conditions but also specific pathogen free (SPF) rats on SPF environment in order to prevent infection. The following results were obtained. 1) In acetic acid ulcer, azuletil sodium (AZE) (greater than or equal to 90 mg/kg/day, p.o.) significantly decreased ulcer index. As estimated on the basis of stage analysis (Ulcer, Healing, Scar), AZE (greater than or equal to 30 mg/kg/day, p.o.) significantly promoted the healing of ulcers. 2) In clamping cortisone ulcer (conventional), AZE (100 mg/kg/day, p.o.) significantly promoted the regeneration of blood vessels. 3) In clamping cortisone ulcer (SPF), AZE at greater than or equal to 30 mg/kg/day and 100 mg/kg/day significantly increased the healing index and mucosal regeneration index, respectively. 4) In clamping cortisone ulcer (SPF), the infection that was observed in the conventional test was not seen at all and the acceleration of healing was observed. Furthermore, the extent of adhesion was also reduced, and the standard errors of various healing indices were smaller. From these results, it is concluded that AZE accelerated the healing of experimentally-induced gastric ulcers in rats.

Increasing effect of sodium 3-ethyl-7-isopropyl-1-azulenesulfonate 1/3 hydrate (KT1-32), a novel antiulcer agent, on gastric mucosal blood flow in anesthetized

Effect of a novel azulene derivative KT1-32 on gastric mucosal blood flow (GMBF) was studied to elucidate its mucosal defensive mechanisms underlying the antiulcer action. The GMBF was measured by two methods which were based on heat clearance and laser Doppler velocimetry in the rat. Intravenous administration of KT1-32 produced a dose-dependent increase in GMBF at doses of 0.3-10 mg/kg; significant increases in GMBF were observed at doses not less than 1 or 3 mg/kg by the laser Doppler or heat clearance method, respectively. The duration of action was about 10 min at 10 mg/kg of KT1-32. A good parallelism in these GMBF changes was noted between both methods. Cetraxate, an antiulcer agent, elicited an increase in GMBF at 30 mg/kg, i.v., when GMBF was measured by the heat clearance method. Sodium guaiazulene 3-sulfonate, another azulene antiulcer agent, showed no increase in GMBF. It is suggested that the increasing effect of KT1-32 on GMBF contributes to its antiulcer activity through strengthening mucosal defensive mechanisms.

Effects of topical application of KT1-32 on transmucosal potential difference and acid secretion in the rat stomach

Effects of intragastric application of azuletil sodium (KT1-32), a novel antiulcer drug, on transmucosal potential difference (PD) and acid secretion were investigated in the rat stomach. The stomach was mounted on a Lucite chamber and perfused with saline before and after exposure to KT1-32 for 10 min. KT1-32 (3-30 mg/kg) produced an elevation of PD in a dose-dependent manner with a rise of the luminal pH. The increased PD response caused by KT1-32 (10 mg/kg) persisted after removal of the agent from the stomach, but this PD generating effect was significantly mitigated by pretreatment with omeprazole (60 mg/kg, i.p.). KT1-32 raised PD under basal conditions, but did not significantly affect the reduced PD response caused by 30% ethanol. In addition, topical application of KT1-32 significantly reduced acid secretion caused by histamine (4 mg/kg/hr, i.v.) and carbachol (20 micrograms/kg/hr, i.v.). In the in vitro study, KT1-32 at 3.9 x 10(-4) M showed 50% inhibition of the H/K ATPase activity prepared from the hog gastric mucosa. These results suggest that KT1-32 exerts locally antisecretory and PD generating effects. The latter may be accounted for by the antisecretory action, which is probably related to the H/K ATPase inhibition.

[General pharmacological properties of an anti-ulcer drug, azuletil sodium (KT1-32)]

Azuletil sodium (AZE, 100 mg/kg, p.o.) did not affect the general behaviors, spontaneous motor activity, pentobarbital-induced hypnosis and body temperature. Furthermore, it did not elicit anticonvulsant and muscle relaxant actions. However, AZE (300 mg/kg, p.o.) elicited a stiff gate and slightly inhibited the spontaneous motor activity and electroshock-induced convulsions. It had no influence on spontaneous EEG activities, even at 30 mg/kg, i.v. AZE inhibited acetic acid-induced writhing moderately at doses above 100 mg/kg. AZE at concentrations up to 10(-5) g/ml did not affect agonist-induced contractions of the isolated ileum, trachea, vas deference and uterus, but inhibited serotonin and oxytocin-induced contraction at concentrations above 3 x 10(-4) and 10(-5) g/ml, respectively; and it also depressed spontaneous movements of the ileum and uterus at concentrations above 3 x 10(-4) g/ml. AZE caused no changes in blood pressure (BP), heart rate (HR), left ventricular pressure, ECG, tracheal pressure (TP), femoral blood flow (FBF) and coronary blood flow (CBF) at doses up to 10 mg/kg, i.v. in anesthetized dogs, but it caused an increase or a decrease in BP, an increase in TP and an increase in CBF at 30 mg/kg, i.v. However, even at 300 mg/kg, p.o., it caused no changes in BP and HR in conscious rats. AZE moderately promoted the charcoal transport. AZE at doses up to 300 mg/kg, p.o. did not affect urine volume, urinary electrolyte excretion, blood glucose and prothrombin time. These results suggest that AZE at anti-ulcer doses of 10-100 mg/kg, p.o. does not have noticeable effects on general pharmacological properties, and there is no marked differences as compared with those of GAS.

Effects of KT-362, a new calcium release blocker, on vascular selectivity and hemodynamic actions in anesthetized dogs

Pharmacological properties of 5-(3-((2-(3,4-dimethoxyphenyl)ethyl)-amino)-1- oxopropyl)-2,3,4,5-tetrahydro-1,5-benzothiazepine fumarate (KT-362), a newly synthesized calcium release blocker, were studied by comparing its vascular selectivity and cardiovascular actions with those of verapamil, a calcium entry blocker. The relaxing effect of KT-362 in rabbit femoral and basilar artery strips contracted with norepinephrine was greater than that in aortic and coronary artery strips. In anesthetized mongrel dogs, KT-362 (0.1-3.0 mg/kg, i.v.) decreased the mean blood pressure, heart rate and total peripheral resistance in a dose-dependent manner, while cardiac output increased slightly despite a decrease in left ventricular pressure. This is consistent with the data on verapamil. Both i.a. and i.v. injections of KT-362 produced a marked dose-dependent increase in vertebral and femoral blood flow. Pretreatment of atropine, propranolol or diphenhydramine exerted no significant effect on the KT-362-induced vasodilation. Verapamil caused a marked increase in the vertebral and coronary blood flows after the injections, but only a slight increase in femoral blood flow. KT-362 at the dose of 10 mg/kg, i.v., had no significant effect on the PQ interval on the electrocardiogram in anesthetized dogs, but 0.1 mg/kg of verapamil increased this interval significantly. These results suggest that KT-362 has properties similar to calcium entry blockers such as verapamil on systemic hemodynamic actions except for the reactivity of vasculatures.

Effects of KT-362, a new Na and Ca influx and Ca release inhibitor, on canine ventricular arrhythmias

Antiarrhythmic effects of the new drug KT-362, which was reported to suppress Na and Ca currents of cardiac cells and also to suppress intracellular Ca release in isolated smooth muscle preparations, were examined using two-stage coronary ligation-, digitalis- and adrenaline-induced ventricular arrhythmias in the dog. Intravenous KT-362 at 10 mg/kg suppressed coronary ligation arrhythmia both at 24 and 48 hr after ligation, and the minimum effective plasma concentrations for arrhythmias induced by 24 hr coronary ligation and 48 hr coronary ligation were 6.1 +/- 1.7 and 8.6 +/- 2.7 micrograms/ml, respectively. Antiarrhythmic effects were accompanied by transient hypotension. Oral administration of 70-100 mg/kg was also effective on 24 hr coronary ligation arrhythmia. However, there was no prominent hypotension in these experiments. Intravenous KT-362 at 3 mg/kg suppressed digitalis arrhythmia; and the minimum effective plasma concentration was 3.3 +/- 1.2 micrograms/ml, which was lower than the effective plasma concentrations for coronary ligation arrhythmias. Intravenous KT-362 at 1 mg/kg also suppressed adrenaline arrhythmia; and the minimum effective plasma concentration was 1.0 +/- 0.1 microgram/ml, the lowest among the effective plasma concentrations. These pharmacological profiles of KT-362 are quite different from those of class 4 Ca antagonists, but similar to those of class 1 drugs such as propafenone. Though KT-362 has a hypotensive effect, it is effective on canine ventricular arrhythmias; thus its clinical usefulness for supraventricular and ventricular arrhythmias is expected.

Thromboxane A2 antagonistic action of a new anti-ulcer agent, azuletil sodium (KT1-32)

The TXA2/PGH2 receptor antagonistic activity of azuletil sodium (KT1-32), a new anti-ulcer agent, was examined. KT1-32 competitively antagonized the contraction of canine gastric arteries induced by U-46619, PGF2 alpha, and PGE2, whereas it had no effect on the PGF2 alpha-, PGE2- and LTD4-induced contraction of guinea-pig ileum, which was not affected by U-46619. In anesthetized dogs, KT1-32 significantly reduced the U-46619-induced decrease in gastric arterial blood flow. Gastric contraction induced by U-46619 in anesthetized rats was markedly inhibited by KT1-32. KT1-32 showed no influence on TXA2 synthetase and cyclooxygenase activities. These results indicate that KT1-32 is a competitive TXA2/PGH2 receptor antagonist, which may be important as to the effectiveness of KT1-32 against gastric ulcer.

Mode of vasorelaxing action of 5-[3-[[2-(3,4-dimethoxyphenyl)-ethyl]amino]-1-oxopropyl]-2,3,4,5- tetrahydro-1,5-benzothiazepine fumarate (KT-362), a new intracellular calcium antagonist

In rabbit aorta, pretreatment with KT-362 (KT; 10(-6) and 10(-5) M) inhibited contractile responses to norepinephrine (NE; 3 X 10(-9)-10(-5) M) and methoxamine (10(-7)-10(-4) M) but failed to affect responses to potassium (10-70 mM). KT (10(-5) M) partially inhibited Ca++-induced contractions in K+-depolarized aorta pre-equilibrated in a Ca++-free medium. After incubation of tissues for 30 min in a Ca++-free medium containing EGTA (0.2 mM), residual responses to NE and methoxamine were inhibited by KT (10(-6)-10(-4) M) and nitroglycerin (10(-5) M), but not by nifedipine, verapamil or diltiazem (all 10(-5) M). The inhibitory action of a combined treatment with KT and nitroglycerin (both 10(-5) M) on the residual response to NE was also much greater than that of either agent alone. In a Ca++-free medium, the residual caffeine-induced contraction of rabbit iliac artery was inhibited by KT (10(-5)-10(-4) M) but not by nifedipine (10(-5) M). The inhibitory action of KT on the residual responses to methoxamine and caffeine in a Ca+-free medium was much greater than that of nitroglycerin. In a Ca++-free medium with low EGTA (0.01 mM), D600 (10(-5) M) and NE (3 X 10(-7) M), the addition of Ca++ (2 mM) resulted in a tonic contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Relaxation of intestinal smooth muscle and calcium movements

The effects of papaverine, isoprenaline and N6,2′-O-dibutyryl 3′,5′-cyclic adenosine monophosphate (DiBu.C-AMP) on calcium movements in the taenia from the guinea-pig caecum have been investigated and compared with the effects of phenylephrine. Papaverine and DiBu.C-AMP antagonized the contraction of KCl-depolarized muscle induced by CaCl2 and increased 45Ca-efflux from the taenia. Papaverine also significantly depressed 45Ca-uptake by this preparation. These findings suggest that papaverine impairs the availability of calcium to the contractile system and that there may be a correlation between relaxation and increase of 45Ca-efflux. The action of DiBu.C-AMP resembles that of papaverine but its potency is less.