RESUMEN
We investigated the effect of chlorpyrifos, an organophosphate insecticide, on Ca2+,Mg2+-ATPase activity of sarcoplasmic reticulum and on contraction dynamics (force and length changes) of Rana temporaria m. tibialis anterior muscle fiber bundles. All of the used concentrations of chlorpyrifos (10-6 to 10-5 M) caused decrease of Ca2+,Mg2+-ATPase activity. The inhibition of Ca2+,Mg2+-ATPase activity by chlorpyriphos in concentrations of 10-6 M to 7.5·10-6 M is due to permeation of sarcoplasmic reticulum rather than due to direct enzyme inhibition by organophosphate insecticides. The inhibitory properties of the compound were higher at increased concentration and exposure timeframes. Chlorpyrifos in concentration range of 10-6 to 7.5·10-6 M causes changes in muscle fiber response force that were more pronounced than changes in contractile length. We demonstrated inhibition of Ca2+,Mg2+-ATPase activity caused by noncholinergic effects of chlorpyriphos. It is possible to conclude that influence of organophosphate insecticides happens not only in the neuromuscular transmission but also on the level of subcellular structures.
Asunto(s)
ATPasa de Ca(2+) y Mg(2+)/antagonistas & inhibidores , Cloropirifos/farmacología , Insecticidas/farmacología , Contracción Muscular/efectos de los fármacos , Fibras Musculares Esqueléticas/efectos de los fármacos , Retículo Sarcoplasmático/efectos de los fármacos , Animales , Fenómenos Biomecánicos , ATPasa de Ca(2+) y Mg(2+)/metabolismo , Calcio/metabolismo , Relación Dosis-Respuesta a Droga , Transporte Iónico/efectos de los fármacos , Contracción Muscular/fisiología , Fibras Musculares Esqueléticas/fisiología , Rana temporaria , Retículo Sarcoplasmático/metabolismoRESUMEN
The processes of change in the rate of generation of power response of artificially ischemic muscle using frequency modulated electrical efferent stimulation were investigated. A strain-gauge technique for registration of contraction process was used. Ischemia was induced by ligating main blood vessels of lower extremity. It is shown that ischemia causes a decrease in muscle performance and reduces maximum frequency of the stimulus signal, which leads to the titanic contraction level. It is shown that the lowering of ischemic muscle strength and reduction of the time that needed to establish a steady state depended on the time of discharge segment in stimulation pattern.
Asunto(s)
Isquemia/fisiopatología , Contracción Muscular/fisiología , Fuerza Muscular/fisiología , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/fisiopatología , Animales , Síndromes Compartimentales/fisiopatología , Vías Eferentes/fisiología , Estimulación Eléctrica , Dinamómetro de Fuerza Muscular , Músculo Esquelético/inervación , RatasRESUMEN
Immune-active substance of Staphylococcus aureus, cell-bound protein A (CBPA), enhances the acetylcholine- or hyperpotassium (K+) Krebs solution-evoked excitation in Taenia coli smooth muscles. CBPA increases caffeine- and carbachole-evoked Ca2+ signals in smooth muscle cells suspension, loaded with indo-1, and also caffeine- and acetylcholine-evoked contraction in smooth muscles slices. Against a background of CBPA-suppressed action of sodium nitroprusside, ATP evokes the membrane depolarization. CBPA in small concentrations potentiates ATPase (Mg2+,Ca2+-; Mg2+- and Mg2+- in the presence of EGTA) activity of actomyosin in the smooth muscles.
Asunto(s)
Señalización del Calcio/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Miosinas/metabolismo , Proteína Estafilocócica A/farmacología , Staphylococcus aureus/metabolismo , Acetilcolina/farmacología , Potenciales de Acción/efectos de los fármacos , Animales , Cafeína/farmacología , Carbacol/farmacología , Células Cultivadas , Colon/citología , Colon/efectos de los fármacos , Colon/enzimología , Colon/metabolismo , Cobayas , Contracción Muscular/efectos de los fármacos , Músculo Liso/citología , Músculo Liso/enzimología , Músculo Liso/metabolismo , Nitroprusiato/farmacologíaRESUMEN
Cell-bound protein A (CBPA), an immune-active substance of Staphylococcus aureus was ascertained to depolarize membrane of taenia coli smooth muscle (SM) cells, depress ATP inhibiting action (or uridinetriphosphate (UTP)) and sodium nitroprusside (SNP). ATP or UTP-induced membrane hyperpolarization increased during first minutes of CBPA exposure. Bacterial substance enhanced and then inhibited fast component of nicotine-induced relaxation of histamine-activated smooth muscles. This enhancement was inhibited by N(omega)-nitro-Larginine, a NO-syntase blocker. CBPA decreased ATP inhibiting action upon histamine-induced contraction, but enhanced cholinergic SM excitation. All these processes are reversible.
Asunto(s)
Adenosina Trifosfato/farmacología , Contracción Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Óxido Nítrico/fisiología , Proteína Estafilocócica A/farmacología , Staphylococcus aureus/metabolismo , Animales , Membrana Celular/efectos de los fármacos , Membrana Celular/fisiología , Colon/efectos de los fármacos , Colon/inervación , Inhibidores Enzimáticos/farmacología , Cobayas , Técnicas In Vitro , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Contracción Muscular/fisiología , Músculo Liso/inervación , Donantes de Óxido Nítrico/farmacología , Óxido Nítrico Sintasa/antagonistas & inhibidores , Nitroprusiato/farmacología , Uridina Trifosfato/farmacologíaRESUMEN
The G-protein-dependent intracellular signal cascades of excitation in longitudinal and circular intestinal smooth muscles (SM) are compared and summarized in the present review. The key mechanism of excitation in longitudinal SM is an activation of electro-mechanical coupling, in that G-proteins, phospholipase A2, arachidonic acid, membrane-bound cyclic adenosine diphosphoribose and Ca2+ are involved. We observed the role of arachidonic acid-activated chorine and voltage-dependent Ca2+ -channels (L-type) in Ca2+ mobilization in these muscle cells. In contrast to longitudinal, the main mechanism of agonist-induced excitation in circular SM is connected with activation of key methabotropical processes. The role of Rho-kinase in mechanisms of Ca2+ --sensitization of contractile apparatus in SM is also shown in this review. A comparative analysis of involvement of different links of signal cascades in initial and sustained phases of contraction in longitudinal and circular SM are also reviewed.
Asunto(s)
Mucosa Intestinal , Intestinos , Músculo Liso , Receptores de Neurotransmisores/metabolismo , Animales , Proteínas de Unión al GTP/metabolismo , Humanos , Mucosa Intestinal/metabolismo , Intestinos/citología , Intestinos/enzimología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Canales Iónicos/metabolismo , Contracción Muscular , Músculo Liso/citología , Músculo Liso/enzimología , Músculo Liso/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Quinasas Asociadas a rhoRESUMEN
The method is proposed for calculation of the most important parameters of the two-stage enzymatic or transport process--modification factors alpha and beta (which characterize the effector action mechanism) as well as the inhibition constant K(i) or activation constant K(a) (characterize the effector affinity for protein). The method was derived as based on the analysis of kinetic regularities of the action of reversible effectors (inhibitors and activators) on the catalytic (transport) activity of proteins. The method is based on the titration of enzymatic (transport) protein by the substrate with the absence and with presence of the effector taken in one of concentrations as well as determination (under the fixed substrate concentration) of the inhibition coefficient i(0.5) (in case of the inhibitor action) or the activation coefficient a(0.5) (in case of the activator action). Practical use of the method has been demonstrated on the example of reversible inhibition to eosine Y (2', 4', 5', 7' - tetrabromofluorescein) ofthe reaction of enzymatic hydrolysis of ATP catalyzed by highly purified transport Ca2+, Mg(2+)-ATPase isolated from the smooth-muscle sarcolemma. In this case the inhibitory effect is characterized by the following parameters: alpha = 6-8 > 1; beta = 0.50-0.53 < 1; inhibition constant K(i) = 10(-9) - 10(-8) M. Consequently, judging from the values of alpha and beta, the eosine Y effect on the analyzed Ca2+, Mg(2+)-dependent ATP-hydrolase enzymatic reaction is based on the mechanism of the mixed inhibition (one can observe the inhibition of the both stages of enzymatic transformation--the substrate binding with the enzyme and decomposition of "Michaelis complex" in the direction of formation of the reaction products). The inhibitor itself, in correspondence with K(ij) values is characterized by rather high affinity for Ca2+, Mg(2+)-ATPase. It is supposed that the proposed approach can be useful when identifying the type of the reversible effector action on the enzymatic (transport) activity of proteins, estimation of real affinity of the inhibitors and activators for the latter.
Asunto(s)
Activadores de Enzimas/química , Inhibidores Enzimáticos/química , Enzimas/química , Modelos Químicos , Cinética , TermodinámicaRESUMEN
The mechanisms of bacterial substances (protein A, peptidoglican Staphylococcus aureus), bacterium toxins (St. aureus, Corynebacterium diphtheriae, Shigella dysenteriae, Clostridium botulinum, Clostridium tetani, Vibrio choleral), transfer factor of immune reactivity to Staphylococcus aureus upon the key link (acetylcholine-, ATP-, inositol-1,4,5-triphosphate-, ryanodin-sensitive receptors, G-proteins, Ca2+, K(+)-transporting systems, second messengers) in the chain of signal conduction of excitatory and inhibitory agonists in excitable cells were examined. The action of these immune-active substances upon contractile proteins ATP-ase activity and protein synthesis was also discussed.
Asunto(s)
Toxinas Bacterianas/toxicidad , Neuronas/efectos de los fármacos , Peptidoglicano/toxicidad , Transducción de Señal , Proteína Estafilocócica A/toxicidad , Animales , Humanos , Músculo Liso/citología , Neuronas/metabolismoRESUMEN
The influence of pH in the medium on ATPase myosin activity in different muscle types was investigated. It has been found that myosin ATPase had two maxima with different values of the specific activity in cardiac, skeletal and smooth muscles depending on pH, namely: 6.0-6.5 and 9.0-9.5. The dependence of physiological properties of different muscle types on the physical-chemical and structural peculiarities of myosin has being discussed.
Asunto(s)
Músculos/enzimología , Músculos/metabolismo , Miosinas/metabolismo , Animales , Bovinos , Estimulación Eléctrica/métodos , Concentración de Iones de Hidrógeno , Músculo Esquelético/enzimología , Músculo Esquelético/metabolismo , Músculo Liso/enzimología , Músculo Liso/metabolismo , Miocardio/enzimología , Miocardio/metabolismo , Conejos , PorcinosRESUMEN
The mathematical model of smooth muscles contractile activity Ca(2+)-dependent control has been proposed on the base of Ca ions trans-sarcomal exchange biochemical mechanisms interpretation in myocytes. While analysing the model the conclusion should be made that kinetic parameters changes (in relation to Ca ions) Mg2+, ATP-dependent calcium pump of plasma membrane--Michaelis constant Km and transport process maximal velocity Vmax-render the effect on the character of the intracellular calcium transients and profile of full mechanokinetic curve. As well one more conclusion has been made that plasma membrane Mg2+, ATP-dependent calcium pump, which kinetic parameters under the physiologic conditions are subjected to modulation as the result of metabolic, pharmacologic and physico-chemical factors fulfills the essential role in supplying Ca(2+)-dependent control of the smooth muscles contractile response full cycle.
Asunto(s)
Calcio/metabolismo , Modelos Biológicos , Músculo Liso/metabolismo , Sarcómeros/metabolismo , Adenosina Trifosfato/metabolismo , CinéticaRESUMEN
Phenomenological mechanokinetic model of the smooth muscle contraction response that based on the idea of separate contraction and relaxation phases additivity realizing in the Ca(2+)-dependent "parallel" dynamic regime was elaborated and tested in the biophysical tensometrical experiment. This model application may be perspective for the further development of conceptions concerning kinetic and energetic regularities of muscle contraction and its quantitative characteristics.
Asunto(s)
Calcio/fisiología , Músculo Liso/fisiología , Animales , Ciego/fisiología , Cobayas , Técnicas In Vitro , Cinética , Modelos Biológicos , Contracción Muscular/fisiología , Relajación Muscular/fisiologíaRESUMEN
The effect of staphylococcus active substances--protein A (PA) and peptidoglican (PG) at concentrations 10(-6)-10(-2) mg/ml on the ATPase activity of pig stomach natural actomyosin and myosin was studied. It was shown that PA and PG at direct contact with smooth muscle contractile proteins caused the activation and inhibition of ATPase activity, respectively. On the basis of this investigation it was assumed that staphylococcal active substances were able to modify of the ATPase activity smooth muscle contractile proteins perhaps via direct action on the myosin molecule, which could be accompanied by conformational changes of the active center of myosin ATPase.