Compound D-600 Research Articles

Effects of compound D600 (methoxyverapamil) on drug-induced contractions of isolated dog uterine muscle

1. 1. The contractile responses of the isolated dog uterus to acetylcholine (Ach), oxytocin (Ot), histamine (Hist) and barium chloride (Ba 2+) were non-competitively blocked by compound D600. This compound was significantly more potent against Ba 2+-induced contractions. 2. 2. Increasing the calcium (Ca 2+) concentration from 0.2 to 2.5 mM reverted the inhibitory effects of D600 against Ach, Ot, Hist and 1 mM Ba 2+. The blockade produced by D600 against 30 mM Ba 2+ was not reversed by increasing the Ca 2+ concentration. 3. 3. In high K +- depolarizing solution, D600 produced a parallel and concentration-dependent displacement to the right to the concentration-response curves of both Ca 2+ and Ba 2+. The Schild plot yielded similar p A 2 values for D600 against Ca 2+ and Ba 2+.

The effect of barium on the contractile mechanism of isolated dog uteri: Influence of the hormonal state

The effect of barium chloride (Ba 2+) on the contractile mechanism of isolated dog uteri was analysed under three different hormonal states: control, estradiol-treated (E) and estradiol + progesterone-treated (E + P). The maximal contractile effect of Ba 2+ was significantly depressed in the E + P group. Tachyphylaxis developed rather quickly ( t 1 2 ≅ 10 min ) to successive additions of 1.0 mM Ba 2+ following the Ca 2+ removal from the nutrient solution. The t 1 2 was further reduced in the E or the E + P groups. No tachyphylaxis was observed when the much higher concentration of 30.0 mM Ba 2+ was employed. In the normal nutrient solution, the calcium-blocker D600 (methoxyverapamil) produced a non-competitive antagonism of Ba 2+ which was not reversed by an increase in extracellular Ca 2+ concentration. In excess-potassium depolarizing solution, the dose-response curves to both Ca 2+ and Ba 2+ were displaced to the right by compound D600. The Schild plot yielded straight lines suggestive of competitive antagonism with the similar pA 2 values of 8.57 for Ca 2+ and 8.35 for Ba 2+. These results suggest that Ba 2+ has a dual mechanism of action on isolated dog uteri, depending on the concentration employed. At low doses (1.0 mM), the contractile effect of Ba 2+ is due to a release of intracellular Ca 2+, an action which can be modulated by the ovarian hormones. The effect of high concentrations of Ba 2+ (30.0 mM) seems to be the result of a direct interaction with the contractile proteins and is independent of the animal's hormonal state. The results also suggest that the access of Ba 2+ to the uterine fibre is possibly through the same Ca 2+ channel which is acted upon by compound D600.

Effect of compound D-600 (methoxyverapamil) on gluconeogenesis and on acceleration of the process by alpha-adrenergic stimuli in rat kidney tubules.

1. Tubule fragments were isolated from renal cortex of fed rats and glucose formation was measured after incubation with 5 mM-sodium lactate. 20 Compound D-600 (10-100 microM) decreased gluconeogenesis from lactate. This inhibition of the process by compound D-600 increased with increasing extracellular Ca2+ concentration, was overridden by noradrenaline and diminished by starvation for 24 h. 3. Inhibition of lactate-supported gluconeogenesis by compound D-600 was not prevented by the alpha 1-adrenoceptor antagonist thymoxamine. 4. Compound D-600 had little effect on gluconeogenesis from 2-oxoglutarate and increased gluconeogenesis from succinate. 5. Compound D-600 opposed stimulation of gluconeogenesis by noradrenaline or oxymetazoline (a selective alpha-adrenoceptor agonist) in a manner suggesting that compound D-600 is an alpha-adrenoceptor blocker. Oxymetazoline was more sensitive than noradrenaline to blockade by both compound D-600 and by the conventional alpha-adrenoceptor antagonist phentolamine. Noradrenaline became more sensitive to blockade by compound D-600 when extracellular Ca2+ was decreased. 6. Compound D-600 did not block stimulation of gluconeogenesis by angiotensin or cyclic AMP.

The role of Ca2+ in the protoveratrine-induced release of gamma-aminobutyrate from rat brain slices.

1. Protoveratrine A increased the release of gamma-amino[3H]butyrate from small slices of rat cerebral cortex. This effect increased with increasing protoveratrine concentration, reaching a maximum at 100 microM. 2. Removal of Ca2+ from the superfusing medium did not change the increase in release due to 10 microM-protoveratrine; however, the Ca2+ antagonists, compound D-600, La3+, Mn2+, Mg2+ and also high Ca2+ concentration inhibited the effect of the alkaloid, as did procaine. 3. Protoveratrine A increased the uptake of 22Na+ into the slices with a similar dose-response curve to that found for gamma-aminobutyrate release. For the most part, the substances that inhibited protoveratrine-stimulated gamma-aminobutyrate release also inhibited 22Na+ uptake, although the correlation was not perfect. 4. Although extracellular Ca2+ is not required for protoveratrine-induced gamma-aminobutyrate release, an increase in Na+ influx that is susceptible to inhibition by some Ca2+ antagonists does appear to be associated with this phenomenon. However, the possibility remains that changes in the free intracellular Ca2+ concentration may be important for transmitter release induced by depolarizing veratrum alkaloids.

Analysis of mechanisms of the positive inotropic action of a protein antigen (egg albumin) and histamine on the myocardium of sensitized guinea pigs

Changes in contractile activity of the myocardium during the local anaphlactic reaction and the action of histamine were investigated in preparations of the left auricle of guinea pigs sensitized beforehand with egg albumin. Histamine (1\10−5 g/ml) and egg albumin (2\10−5 g/ml) caused little change in the first (after 3 min of rest) contraction of the preparation, but considerably enhanced the increase in amplitude of contractions in a rhythmic series (positive “Bowditch's ladder”). The higher the frequency of stimulation (between 1 and 5 Hz) of the preparation, the stronger the positive inotropic effect of histamine and egg albumin. Inactivation of fast Na channels by depolarization of the membrane of the myocardial cells in medium with a high potassium concentration (13.7 mM KCl) did not abolish these effects of histamine and the antigen. Conversely these effects were completely suppressed by blocking of the slow Na, Ca channels by compound D-600 (1\10−6 g/ml).

Comparative analysis of the action of papaverine, isoprenaline, La3+, and compound D-600 on depolarized guinea pig taenia coli smooth muscle

Decreased self-maintenance ability of the migrating stem cells (CFU) from the peripheral blood or ectopic focus of hemopoiesis in comparison to the settled bone marrow CFU, as measured by the spleen colony method or by means of chromosomal markers, has been studied. The competence for myeloid and lymphoid differentiation was essentially the same for migrating and settled stem cells.

Effect of presynaptic neurotoxins from bee and cobra venom on spontaneous mediator secretion from mouse motor nerve ending

Experiments were carried out on the papillary muscles prepared from the rabbit heart 10, 60 or 180 minutes after exposure of the animals to thermal burn. Isometric tension in the changing stimulation frequency of the preparation (the range being 0.1-2.0 Hz) and in post-stimulating potentiation was recorded. It was shown that the disturbance degree of the myocardial contractile activity caused by the burn rose depending on increased shock duration. It was evidenced by the following findings: in all the papillary muscles prepared 3 hours after burn and in 50% of the preparations taken one hour after the injury the "biphasic" dependence frequency power (F-P) peculiar to healthy myocardium changed to "monophasic" one (contraction amplitude progressively decreased on the frequency growing), and poststimulating potentiation, absent in the normal myocardium state, appeared. Within 10-minute shock duration only several preparations revealed poststimulating potentiation, F-P changes being absent. Normal rhythmoinotropic relationships in the myocardium restored under the influence of two-fol increase of (Ca2+)o or under prolonged (3-4 hours) perfusion of the preparation with normal Tyrode's solution. The changes observed in the myocardium rhythmoinotropic relationships produced by the burn shock were similar to those occurred as a result of the calcium canals block by the compound D-600.

Changes in contractile activity of the rabbit myocardium as a result of burn shock of varied duration

Experiments were carried out on papillary muscles isolated from the rabbit heart 10, 60, or 180 min after thermal injury to the animal. Isometric contractions were recorded during stimulation of the preparation at changing frequencies (within the range from 0.1 to 2 Hz) and during poststimulation potentiation. The degree of disturbance of myocardial contractility as a result of burns was found to increase with an increase in the duration of burn shock: In all the papillary muscles isolated 3 h after burning and in 50% of those isolated 1 h after burning the “biphasic” frequency-strength (f-P) relationship characteristic of the normal myocardium was converted into “monophasic” (the amplitude of the contractions decreased progressively with an increase in frequency) and poststimulation potentiation, normally absent, appeared. After shock lasting 10 min, poststimulation potentiation was observed only in some preparations and no change in f-P was present. The normal inotropic relationships of the myocardial rhythm were restored after a twofold increase in [Ca++]0 or after prolonged (3–4 h) perfusion of the preparation with normal Tyrode solution. Changes in inotropic relationships of the myocardial rhythm in burn shock were similar to the changes in f-P observed after blockade of the calcium channels with compound D-600.

Effect of diazoxide, verapamil and compound D600 on isoproterenol and calcium-mediated dose-response relationships in isolated rabbit atrium

The effect of diazoxide, verapamil and compound D600 on calcium and isoproterenol dose-response relationships was investigated in isolated rabbit atrial preparations. All three agents shifted calcium dose-force relationships parallel and to the right. D600 acted as a competitive antagonist of calcium, as a plot of log (x − 1) vs. − log B resulted in a straight line with a slope of approximately −1.0. Diazoxide, verapamil and D600 also antagonized isoproterenol but in a non-competitive manner. A reduction of calcium in the bathing fluid produced a qualitatively similar non-competitive antagonism of isoproterenol and markedly potentiated diazoxide antagonism of isoproterenol. We conclude that: (1) diazoxide has calcium antagonistic properties similar to the “calcium antagonists” verapamil and D600; (2) these agents act as competitive antagonists of calcium through a specific site that is beyond the β-adrenergic receptor and in the series of events between the β-adrenergic receptor and inotropic response in myocardial tissue.

Effect of biologically active substances (acetylcholine, histamine, and bradykinin) on depolarized smooth muscle of the taenia coli

Experiments on isolated strips of the guinea pig taenia coil showed that compound D-600, which blocks calcium channels, depresses the contractile response of depolarized smooth muscle to administration of acetylcholine (5·10−6), histamine (2·10−6), and bradykinin (10−5 g/ml). Besides depressing the effect of biologically active substances, compound D-600 also depresses the “potassium contracture”. It is postulated that the biologically active substances activate the flow of Ca++ ions through the surface membrane but not the discharge of Ca++ from the sarcoplasmic reticulum.

RELATIONSHIP BETWEEN EFFECTS OF PROCAINE AND Ca ON SPONTANEOUS ELECTRICAL AND MECHANICAL ACTIVITIES OF THE SMOOTH MUSCLE CELLS OF THE GUINEA PIG URINARY BLADDER

The relationships between the effects of procaine and those of Ca on the spontaneous electrical and mechanical activities of smooth muscle cells of the guinea pig urinary bladder were studied using both microelectrode and sucrose gap methods. Procaine(1, 7, and 15mM) depolarized the membrane and increased spontaneous spike freqency. The maximum rates of rise and fall and the after-hyperpolarization of the spike decreased. Enhanced spontaneous rhythmic contractions accompanied these membrane activities (1 mM). The tone of the preparation (resting rension) increased transiently and decreased gradually (7-15mM). These procaine effects were suppressed by the application of excess Ca (7.5 mM). The increased electrotonic potential induced by 7mM procaine was reduced by the addition of 7.5 mM Ca. Reduction of Ca concentration (0.8 and 0 mM) IN Krebs solution containing procaine further depolarized the membrane and decreased the spike amplitude. In Ca-deficient solution, the enhanced rhythmic contractions induced by procaine were slightly reduced. Compound D600 (1-3mg/1), manganese ion (Mn) (1-3 mM), and cobalt ion (CO) (1-3 MM) inhibited the effects of procaine on spike discharges and mechanical responses. From these results it is concluded that procaine action is related to that of Ca which controls the membrane permeability, since procaine depolarizes the membrane by reducing K conductance. Furthermore, action potentials observed in the Krebs solution containing procaine are considered to be Ca spikes, which seem to play an important role in excitation-contraction coupling in the guinea pig urinary bladder smooth muscle.

Effect of histamine on electrical and mechanical activity of the myocardial fibers of the guinea pig heart after blocking of the fast sodium channels

The effect of histamine on electrical (recorded intracellularly) and mechanical (isometric contraction) activity of the auricular myocardial fibers of the guinea pig atrium was investigated after preliminary blocking of the fast sodium channels by prolonged depolarization with K+ ions (20 mM) or with tetrodotoxin (3.2×10−7−2.0×10−6 g/ml). Slowly increasing gradual responses to short stimuli were found to appear in the depolarized fibers. Histamine (10 μg/ml) increased the amplitude and duration of these responses, and at the same time the amplitude of the contractions of the preparation also increased. Compound D-600 (1 mg/liter), which specifically blocks calcium channels, inhibited the slow responses and mechanical activity of the preparation. After administration of tetrodotoxin alone orin combination with KCl, histamine also had a potentiating action of its own. It is concluded that histamine activates the slow sodium-calcium channels of the myocardial excitable membrane.

Effect of Beta-Adrenergic Stimulation on Myocardial Adenine Nucleotide Metabolism

The effects of isoproterenol, propranolol, and compound D600 (α-isopropyl-α-[( N -methyl- N -homoveratryl)-γ-aminopropyl1-3, 4, 5-trimethoxyphenylacetonitrile) on myocardial adenine nucleotide metabolism were studied in rat hearts in situ. Isoproterenol in doses between 0.1 and 25 mg/kg induced an increase in heart rate concomitant with a significant acceleration in the de novo synthesis of adenine nucleotides (ATP, ADP, and AMP) and a diminution in their concentration. The effects of isoproterenol were antagonized by propranolol (1 and 50 mg/kg), which alone caused a reduction in the de novo synthesis of adenine nucleotides without inducing a change in their concentration. Compound D600 (10 mg/kg) brought about a slight elevation in the concentration of adenine nucleotides but did not influence the rate of de novo synthesis. The isoproterenol-induced diminution in adenine nucleotide concentration was prevented by D600; under these conditions, the acceleration of de novo synthesis was attenuated. These findings indicate that de novo synthesis of myocardial adenine nucleotides in the normal and the isoproterenol-stimulated heart is regulated not only by a feedback mechanism dependent on the concentration of adenine nucleotides but also by β-receptor-mediated alterations in carbohydrate metabolism which can cause changes in the size of the available pool of 5-phosphoribosyl-1-pyrophosphate.

A study of compounds which inhibit vascular smooth muscle contraction

Several compounds have been examined for their inhibitory action on a rat aortic ring preparation stimulated by four different agonists, noradrenaline bitartrate (NA), Ba 2+, Ca 2+ and K +. The compounds tested include phentolamine, papaverine, cinnarizine, cyclandelate, SKF-525A, prenylamine, guancydine, verapamil and compound D-600. Phentolamine inhibited NA reponses at much lower concentrations than those required to antagonize K +, Ca 2+ or Ba 2+ responses. Guancydine was also more effective against NA but was much less potent than phentolamine in this respect. Papaverine, cinnarizine, cyclandelate, prenylamine and SKF-525A were non selective agents and inhibited responses to all agonists approximately equally at various concentrations. Verapamil and D-600 were highly potent compounds which were more effective against cation-induced responses, especially those to Ca 2+, than against those induced by NA.