Selective potentiating effects of metal ions on vasopressom

Zusammenfassung Der Effekt von Na⁺-, NH₄ ⁺- und Ca⁺⁺-Ionen auf die Blutdruckaktivität von Arginin-Vasopressom wurde untersucht und mit analogen Experimenten (Val⁵-Angiotensin II-Asp¹--Amid) verglichen. Die Wirkungsweise der Ionen-induzierten Potenzierung von Vasopressin wird diskutiert.

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Supported by USPHS Grant No. AM-13567.

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Abbreviations used are: AVP, arginine-vasopressin; bp, blood pres sure; U, unit;n, number of experiments; , mean value; S.E. standard error;p, level of significance; NS, not significant.     

Possible role of intestinal alkaline phosphatase activity in thiamine transport

Summary Thiamine deficiency caused a marked decrease of intestinal alkaline phosphatase (al-Pase) activity, but had no effect on the Ca⁺⁺-ATPase activity and Ca⁺⁺-absorption in rats. The al-Pase activity was significantly decreased 1 h after oral administration of ethanol at 0.5 and 2.5 g/kg. In contrast, Mg⁺⁺-, Ca⁺⁺- and (Na⁺+K⁺)-ATPase activities did not change after the administration of ethanol. These findings show that the al-Pase activity, unlike the Ca⁺⁺-ATPase activity, is not related to Ca⁺⁺-absorption. A possible role of al-Pase activity in the active transport of thiamine in the intestine was discussed.     

Die Abhängigkeit der Ca++-Aufnahme isolierter Mitochondrien des Herzmuskels von der Na+-und K+-Konzentration als mögliche Ursache der inotropen Digitaliswirkung

Summary In isolated mitochondria of heart muscle from rabbits and oxen there is, under suitable conditions, an accumulation of Ca⁺⁺, which is significantly enhanced by elevating the K⁺/Na⁺ quotient of the incubation medium. K-strophanthine (10^–5–10^–7) does not influence the accumulation of Ca⁺⁺ by the mitochondria of heart muscle. Therefore the intracellular increase in exchangeable Ca⁺⁺ observed after digitalis-glycosides could be explained by a decrease of the intracellular K⁺/Na⁺ quotient, which is caused by inhibition of the membrane ATPase and diminishes the capacity for Ca⁺⁺ accumulation in mitochondria.     

New selective inhibitors of the transmembrane Ca conductivity in mammalian myocardial fibres. Studies with the voltage clamp technique

Zusammenfassung Die Ca⁺⁺-Leitfähigkeit der Myokardfaser-Membran wird durch Verapamil und sein Methoxyderivat D 600 teilweise bis zum vollständigen Verlust reduziert. Dieser Effekt erfolgt selektiv, da die Na⁺-Leitfähigkeit der Membran unbeeinflusst bleibt. Die während der Erregung der Myokardfaser fliessenden transmembranären Ca⁺⁺- und Na⁺-Ströme benutzen demzufolge voneinander unabhängige Membrankanäle.     

Biological effects of lithium: Experimental analysis in plant cytokinesis

Summary The biological effects of lithium ions have been studied, using plant cytokinesis in onion root meristems as the experimental model. Lithium induces binucleate cells by inhibiting cell plate formation. Moreover, lithium and caffeine have additive effects on the induction of binucleate cells. Na⁺, K⁺, Ca⁺⁺ and Mg⁺⁺ antagonize lithium-induced inhibition of cytokinesis.     

An analysis of the effects of urethane on cardiovascular responsiveness to catecholamines in terms of its interference with Ca++ mobilization from both intra and extracellular pools

Summary Urethane (1×10^–2–1×10^–1 M) reduced, in a concentration-dependent manner, both intra and extracellular Ca⁺⁺ dependent noradrenaline-induced contractions of perfused rabbit ear artery as well as the tonic contractions produced by perfusion with high K⁺ solution. However, a quantitative analysis of the data indicated that for urethane concentrations similar to those found in plasma during anesthesia urethane antagonism is confined to noradrenaline-induced contractions which depend upon the mobilization of Ca⁺⁺ from intracellular storage sites. In KCl-contracted arteries, urethane enhanced the relaxant effects of isoprenaline.—Urethane reduced the amplitude of contractions of spontaneously beating guinea-pig right atrium at concentrations which have only a limited effect on frequency. In addition, it decreased in a concentration-dependent manner the amplitude of isoprenaline-activated electrically driven, and K⁺ depolarized guinea-pig right ventricular strips. Urethane had no effect on the chrono and inotropic actions of isoprenaline on cardiac preparations. In in vivo experiments the chronotropic response to low doses of isoprenaline was significantly higher in urethane-treated as compared to unanesthetized rats. The higher dose of isoprenaline tested produced a significant fall in systolic blood pressure in urethane-anesthetized rats. A significant correlation exists between the chronotropic response to isoprenaline and resting heart rate values in urethane-anesthetized rats. These results indicate that urethane, at concentrations similar to those found in plasma during anesthesia selectively interferes with mobilization of Ca⁺⁺ from intracellular storage sites. In addition, the interference of urethane anesthesia with the isoprenaline chronotropic effect in vivo cannot be explained by a direct interference of urethane with -adrenoceptors at cardiac level.     

Extracellular space values and intracellular ionic concentrations in the isolated midgut of Philosamia cynthia and Bombyx mori

Summary Total extracellular space values have been determined in the midguts of 2 lepidopteran larvae, Philosamia cynthia and Bombyx mori. The values found are 42% and 45% tissue water respectively. Intracellular concentrations of Na⁺, Ca⁺⁺ and Mg⁺⁺ are very low, while K⁺ concentration is 197.2 mEq/l cell water in Philosamia and 180.9 mEq/l cell water in Bombyx.     

Zinc antagonizes the effect of botulinum type A toxin at the mouse neuromuscular junction

Summary Zn²⁺ (10–100 M) elevated the frequency of miniature end-plate potentials (MEPPs) in the mouse diaphragm. The effect did not depend on external Ca²⁺. Botulinum type A toxin (BTX_A, 50 ng/ml) abolished MEPPs almost completely within 30 min. Zn²⁺ (100 M) restored MEPPs and increased their frequency after they had been abolished by BTX_A in Ca²⁺-free solutions. The antagonistic effect of Zn²⁺ in the Ca²⁺-free solution was reduced by exposing the diaphragm to the toxin in the Ca²⁺-free solutions containing high K⁺. Thus, the action of BTX_A is probably enhanced by depolarization of the motor nerve terminals.     

Potentiation by taurine of the inotropic effect of ouabain and the content of intracellular Ca++ and taurine in the heart

Summary Under certain conditions, taurine (3.0 mM) potentiated cardiac contractile response to ouabain in the normal medium. The potentiation by taurine was also observed in the low K⁺ medium, in which the positive inotropic effect of ouabain increased. The potentiation as seen in both media was, at least in part, due to the increase by taurine of Ca⁺⁺ content in the heart. Taurine in the heart was not directly related to this potentiation.     

Effects of prostaglandin E1 on45Ca++-incorporation and spike activity in longitudinal smooth muscle of cat jejunum

Summary Prostaglandin E₁ (0.3 M) decreased both the⁴⁵Ca⁺⁺-incorporation and the spike activity in isolated longitudinal smooth muscle preparations of the cat jejunum probably by an inhibition on the Ca⁺⁺ influx.     

Free flow electrophoresis of isolated secretory granules from bovine neurohypophyses

Zusammenfassung Sekretorische Granula aus der Neurohypophyse von Rindern wurden durch Ultrzentrifugierung isoliert. Frei-Fluss Elektrophorese dieser Partikel zeigte, dass sie eine negative Ladung besitzen. Ca⁺⁺ und Na⁺ verminderten die Mobilität der Granula im elektrischen Feld.     

Influence de la vagotomie chez la tancheTinea tinca au cours d'une surcharge pluricationique (eau de mer diluée). Variation des cations Na+, K+, Ca++ et de l'intensité de la respiration tissulaire

Summary Respiratory ionic content (Na⁺, K⁺, Ca⁺⁺) of hepatic tissue and ionic excretion measurements were performed in the TenchTinea tinea kept in diluted sea water. After bilateral section of parasympathetic system, the changes of Na/K value are less than in fresh water. The survival and hepatic O₂ uptake were the same. It is suggested than after both vagi section sea water Ca⁺⁺ allowed a best osmoregulation in this species.

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Ce travail a été réalisé avec la collaboration technique de A.Rup.     

Skinned smooth muscle: Time course of force and ATPase activity during contraction cycle

Summary The time course of ATPase activity and force has been determined during contraction and relaxation in skinned (hyperpermeable) anterior byssus retractor muscle, ABRM, ofMytilus edulis and compared with corresponding measurements on skinned taenia coli of guinea-pigs. Following a calcium-induced contraction, lowering the [Ca⁺⁺] to 10^–8 M rapidly reduces ATPase activity within 2 min to resting levels while force declines only to about 30–50% of maximal tension within the same time. Thus slow relaxation is due to a catch-like-state which is common to different kinds of smooth muscles and can be reduced with cAMP in ABRM and by P_i in taenia coli.The support by the Deutsche Forschungsgemeinschaft and the excellent technical assistance of Mrs K. Winnikes are gratefully acknowledged.     

Phosphorylation of cockroach antennal polypeptides: effects of second messengers and pheromonal blend

In insect antennal extracts, Schleicher et al.¹ showed that protein kinase C (PKC) inhibitors abolish the transience of pheromone-induced rapid inositol trisphosphate responses, which suggests that pheromonal signals act on phosphorylation of specific proteins. To confirm this hypothesis, we studied the effects of second messengers and a pheromonal blend on phosphorylation of antennal proteins in the cockroachPeriplaneta americana. Proteins from adult male antennae were phosphorylated in vitro in the presence of [³²P] triphosphate, then separated by SDS-polyacrylamide gel electrophoresis. Numerous phosphopolypeptides were visualized. The presence of Ca⁺⁺/calmodulin in the incubation medium resulted in increased phosphorylation of polypeptides with molecular weights of 38, 48, 51, 54 and 58 kDa. Stimulation of PKC by addition of Ca⁺⁺ phosphatidylserine (PS)/phorbol myristate acetate (PMA) resulted in the appearance of three phosphopolypeptides of 36, 70 and 120 kDa. In the presence of cyclic adenosine monophosphate, two new major polypeptides of 46 and 42 kDa appeared; the latter polypeptide also appeared in the presence of cyclic guanosine monophosphate. Comparison with polypeptide composition of tissue from the cerci, leg, brain and fat body showed that the 36 and 48 kDa polypeptides were specific to antennae, whereas the 120 kDa polypeptide was also present in the adult brain. When antennae are subjected to pheromonal stimulation for 16 seconds prior to homogenization, in vitro phosphorylation of the 120, 70, 64 and 38 kDa polypeptides was inhibited, whereas phosphorylation of the 58, 54, 51 and 48 kDa polypeptides was strongly stimulated. It is noteworthy that a 107 kDa polypeptide was observed only after pheromonal stimulation by Ca⁺⁺/PS/PMA. Our findings suggest that Ca⁺⁺-and PKC-dependent protein phosphorylation systems play an important role in the transduction of pheromonal signals in antennae of male cockroachP. americana. We speculate that specific phosphoproteins may modulate sensitivity and signal amplification during the olfactory transduction process.     

Hypothyroidism lowers blood pressure,adenylate cyclase and Na+, K+-and K+, Ca++-ATPase activities in normotensive and spontaneously hypertensive rats

Summary Myocardial isoproterenol-stimulated adenylate cyclase, Na⁺, K⁺-ATPase and K⁺, Ca⁺⁺-ATPase activities are elevated in the spontaneously hypertensive rat and can be lowered by methimazole-induced hypothyroidism which also prevents the development of hypertension. Although thyroid hormone levels are similar between untreated SHRs and WKY rats, the thyroid is apparently necessary for the expression of spontaneous hypertension.Acknowledgments. Supported by North Carolina Heart Grant No. 40301 and a grant from Sigma Xi.     

Demonstration of a negative binding effect of bovine growth hormone toward potassium

Zusammenfassung Hochgereinigtes Rinderwachstumshormon besitzt ein ziemlich gutes Bindungsvermögen für Mg⁺⁺-, Ca⁺⁺- und Na⁺-Ionen. Andererseits wird K⁺ je nach Konzentration überhaupt nicht, oder nur in Spuren gebunden.

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The performance of the elementary analyses by R. C.Anderson is gratefully acknowledged. Thanks are also due to B.Czuk and N. O.Milkovich for technical assistance.     

Enhanced excitability in locust muscle fibres induced by calcium free saline

Summary The membrane of locust muscle fibres normally exhibits a graded electrical response to outward current pulses of increasing strength. On removal of Ca⁺⁺ ions from the external medium, these fibres are shown to exhibit depolarizing membrane responses of variable time course and duration. These responses are abolished in Na⁺-free solutions, and by the addition of Mn⁺⁺ ions.D.A.M. was the recipient of a Royal Society and Science Research Council European Exchange Fellowship. We thank the Centre for Overseas Pest Research, Kensington for supplying the locusts.     

Sensitivity of the developing chick myocardium to the positive inotropic effects of calcium and isoproterenol

Summary The present results show that the sensitivity of the chick myocardium to the positive motropic effect of Ca⁺⁺ decreases during development and that the Ca⁺⁺ concentration of the physiological solution used must be lowered below normal to study the effects of positive inotropic agents in preparations from younger embryos. Isoproterenol elicits positive inotropic responses in 7–9-day embryonic ventricle and in newborn chick atria; however, the 4-day embryonic myocardium is unresponsive to isoproterenol.This work was supported by Grant No. HL-15995 from the National Heart Institute (USPHS).The authors would like to thank Dr.F. E. Shideman for the isolated tissue baths used in these experiments.     

Phosphoproteinphosphatase activity in sea urchin embryos

Riassunto Si è studiata l'attività fosfoproteinfosfatasica in omogenati totali di uova ed embrioni diParacentrotus lividus e diArbacia lixula. La reazione ha un optimum a pH acido, è stimolata da K⁺ e Na⁺ ed è inibita da Ca⁺⁺ e Mg⁺⁺. L'attività enzimatica aumenta tra la fecondazione e lo stadio a 64 blastomeri; in seguito rimane costante fino a blastula con mesenchima; quindi generalmente decresce.

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This work has been supported by a grant from the Consiglio Nazionale delle Ricerche to the Laboratory of Comparative Anatomy (Research Group of Embryology).     

Development of the maximum isometric force at short sarcomere lengths in calcium-activated muscle myofibrils

Summary Studies on the sarcomere length-force relation in Ca⁺⁺-activated vertebrate muscle myofibrils indicate that the maximum isometric force can be generated even at sarcomere lengths around 1 m, indicating that the ascending limb of the sarcomere length-force relation is virtually absent.We thank Miss S. Gomi for her technical assistance. This work was supported by the grant (No. 587028) form the Ministry of Education, Science and Culture of Japan.