Differential effects of ethanol on prostaglandin responses of arterial and venous smooth muscles.

The present results, using isolated rat aortic strips and portal vein segments, demonstrate that ethanol, depending upon concentration, can either enhance or attenuate the contractile actions of PGF2alpha on at least 2 different types of vascular smooth muscle. At the very least, the present findings question that the use of ethanol as a solvent when investigating the contractile actions of PG molecules on smooth muscles.     

Ethanol reduces Ca2+ concentrations in arterial and venous smooth muscle

Summary The present results, using isolated rat aortic strips and portal vein segments, demonstrate that ethanol (170–430 mM) significantly inhibits calcium uptake in these 2 different types of vascular smooth muscle.Supported by NIH grant No. HL-18015 and NIMH grant No. MH-26236. Request for reprints should be addressed to B.M. Altura.     

Ethanol reduces Ca2+ concentrations in arterial and venous smooth muscle.

The present results, using isolated rat aortic strips and portal vein segments, demonstrate that ethanol (170--430 mM) significantly inhibits calcium uptake in these 2 different types of vascular smooth muscle.     

Ca2+ uptake and distribution in alloxan-diabetic rat arterial and venous smooth muscle

Summary This report demonstrates that in experimental diabetes mellitus (DM) calcium uptake and its distribution is altered in rat aortic but not in portal venous smooth muscle. Results are interpreted as consequences of increased calcium binding by aortic smooth muscle in experimental DM, which could account for the hyporeactivity of alloxan diabetic rat aorta reported previously.Supported by NIH grant No.HL-18015 and NIDA grant No. DA-02339.     

Velocity and myosin phosphorylation transients in arterial smooth muscle: effects of agonist diffusion

Summary Transients in myoplasmic [Ca²⁺] and in phosphorylation of the 20,000 dalton light chain of myosin have been reported following stimulation of vascular smooth muscle by various agonists. Since these transients are rapid compared with the time required to attain a steady-state stress, agonist diffusion rates may be a significant limitation in activation. The purpose of this study was to estimate the effect of agonist diffusion rates on the time course of activation as assessed by mechanical measurements of stress development and isotonic shortening velocities and by determinations of the time course of myosin phosphorylation. The approach was to measure these parameters in K⁺-stimulated preparations of the swine carotid media of varying thicknesses and to estimate the theoretical contributions imposed by diffusion rates and the presence of a diffusion boundary layer surrounding the tissue. The results show that the time course of parameters which are tissue averages such as stiffness, active stress, and myosin phosphorylation is dominated by agonist diffusion rates. The sequence of events involved in excitation-contraction coupling including agonist actions on the cell membrane, Ca²⁺ release, activation of myosin light chain kinase, and cross-bridge phosphorylation appear to be very rapid events compared with stress development. Estimates of unloaded or lightly loaded shortening velocities which are not simple tissue averages appear to provide an imporoved estimate of activation rates.Supported by a grant from the National Institutes of Health 5-PO1-HL19242. K. E. Kamm was supported by a National Heart, Lung, and Blood Institute Research Service Award HL-05957.     

Velocity and myosin phosphorylation transients in arterial smooth muscle: effects of agonist diffusion

Transients in myoplasmic [Ca2+] and in phosphorylation of the 20,000 dalton light chain of myosin have been reported following stimulation of vascular smooth muscle by various agonists. Since these transients are rapid compared with the time required to attain a steady-state stress, agonist diffusion rates may be a significant limitation in activation. The purpose of this study was to estimate the effect of agonist diffusion rates on the time course of activation as assessed by mechanical measurements of stress development and isotonic shortening velocities and by determinations of the time course of myosin phosphorylation. The approach was to measure these parameters in K+ -stimulated preparations of the swine carotid media of varying thicknesses and to estimate the theoretical contributions imposed by diffusion rates and the presence of a diffusion boundary layer surrounding the tissue. The results show that the time course of parameters which are tissue averages such as stiffness, active stress, and myosin phosphorylation is dominated by agonist diffusion rates. The sequence of events involved in excitation-contraction coupling including agonist actions on the cell membrane, Ca2+ release, activation of myosin light chain kinase, and cross-bridge phosphorylation appear to be very rapid events compared with stress development. Estimates of unloaded or lightly loaded shortening velocities which are not simple tissue averages appear to provide an improved estimate of activation rates.     

Mechanisms of sympathetic regulation of arterial smooth muscle

Zusammenfassung Der Wirkungsbereich der Querschnittsregulation der A. dorsalis pedis durch den Sympathikus bei Hunden wurde erfasst und die Relation Reizerfolg-Reizfrequenz durch eine Hyperbel charakterisiert. Mittels Fluoreszenzmethode gewonnene Befunde weisen darauf hin, dass die durch Sympathikusreizung freigesetzen Monoamine zu den nervenfreien Mediaschichten diffundieren.

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For the supply of Nialamide we are indebted to Pfizer Corporation, Eastern Europe Division.     

Types of cell contacts in arterial smooth muscle

Zusammenfassung Nachweis, dass in Arteriolen sowie in präkapillaren Arteriolen des Hunde-Duodenums nur eine einfache Aneinanderlagerung der Muskelzellen erfolgt und keine gap junctions, wie sie in den Muskelschichten der Hohlwandorgane vorhanden sind.     

Colchicine-induced appearance (proliferation) of smooth sarcoplasmic reticulum in arterial smooth muscle cells

Colchicine treatment resulted in the appearance and proliferation of smooth sarcoplasmic reticulum in some smooth muscle cells of the aortic and pulmonary trunk walls in the rabbit. The significance of cytoplasmic microtubules and/or membrane-bound tubulin for the morphogenesis, functioning and control of smooth endoplasmic reticulum in different kinds of cells is discussed.     

Colchicine-induced appearance (proliferation) of smooth sarcoplasmic reticulum in arterial smooth muscle cells

Summary Colchicine treatment resulted in the appearance and proliferation of smooth sarcoplasmic reticulum in some smooth muscle cells of the aortic and pulmonary trunk walls in the rabbit. The significance of cytoplasmic microtubules and/or membrane-bound tubulin for the morphogenesis, functioning and control of smooth endoplasmic reticulum in different kinds of cells is discussed.     

Calcium and the contractile response to prostaglandin in the smooth muscle of guinea-pig stomach

Summary In the longitudinal smooth muscle of guinea-pig stomach, verapamil (10^–5 M) which showed marked suppression of high K-induced contractures, did not suppress the contractile response to PGE₁ (1.5×10^–9 to 10^–6 M) markedly. These results suggest that the contractile mechanism of PGE₁ in guinea-pig stomach may mainly depend on a release of bound Ca in the cell and partly depend on a Ca influx from the extracellular origin.     

Effect of lidoflazine on norepinephrine,angiotensin and serotonin responses in isolated smooth muscle preparations

Résumé Les effets de la lidoflazine ont été étudiés sur les bandelettes aortiques isolées du lapin et les bandelettes gastriques isolées du rat. La lidoflazine antagonise significativement la sérotonine sur ces 2 préparations sans altérer leurs réponses à l'angiotensine et à la noradrénaline.     

Prostaglandin-like substances in Propionibacterium acnes. III. Differential contractile effects on smooth muscle layers of the human utero-tubal junction.

The biological activity of a lipid fraction extracted from P. acnes was tested on isolated smooth muscle strips from the human utero-tubal junction. The bioassay experiments support the concept that prostaglandin-like substances (PLS) occur in P. acnes. However, in the bioassay system used, the effect of PLS was different from that of PGF2 alpha and PGI2 but similar, although not identical, to that of arachidonic acid and PGE2.     

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.     

Low temperature-induced contracture of depolarized smooth muscle and the effects of calcium and multivalent cations

Summary Lowering of temperature caused tension development in the smooth muscle of the guinea-pig vas deferens, which was dependent on extracellular Ca. Mn²⁺ and La³⁺ reversed the effect and induced phasic contraction on rewarming.Part of the results were presented at the 14th Int. Congress of Physiological Science, Budapest 1980.     

Energy metabolism and transduction in smooth muscle

Early investigations into the nature of the coupling between energy transduction and metabolism in smooth muscle, particularly from the laboratories of Bülbring and Lundholm, suggested that specific metabolic pathways could independently supply energy for ion transport and actin-myosin interactions. Subsequent work has solidified the concept that oxidative phosphorylation is specifically coupled to tension generation and maintenance, whereas, aerobic glycolysis is not only a vital characteristic of smooth muscle metabolism, but also is likely to be independently coupled to Na-K transport at the plasmalemma. The independence of oxidative and glycolytic metabolism is reflected as a compartmentation of carbohydrate metabolism in the porcine carotid artery. The coupling of these independent metabolic pathways with specific energy utilizing processes, indicates a means by which energy production and transduction can be closely and efficiently regulated. The coupling of glycogenolysis to mitochondrial respiration may have evolved as a direct response to the energetic needs of VSM. That is, the large glycogenolytic response in the initial minutes of stimulation may be necessary to maximize the cellular production of ATP during the presteady state. Likewise, the coupling between aerobic glycolysis and Na-K transport indicates a sensitive and efficient means of coordinating energy metabolism with ion transport at the membrane level. Additionally, the regulation of substrate supply, i.e. glucose transport, also may be closely coordinated with changes in ion transport. One may speculate that alterations in the microenvironment of each compartment can independently regulate intermediary metabolism and therefore allow the cell to quickly and efficiently respond to localized stimuli. Thus, stimulation of Na-K transport could effectively regulate energy production at the membrane level without mobilizing or competing with the energy transduction of other cellular processes. This compartmentation of energy utilization may be highly advantageous, since oxidative metabolism is closely coordinated with mechanical activity and therefore regulation of blood flow. Future investigations will attempt to elucidate which intracellular signals which are responsible for the regulation of these functionally independent compartments of energy metabolism and transduction in VSM. In more general terms, our findings provide a basis from which future questions concerning the regulation of cellular metabolism must be directed. The cellular cytoplasm can no longer be envisioned as a homogeneous compartment, but rather a complex array of functional subcompartments which may be individual