ABSTRACT
The study was conducted in normotensive and spontaneously hypertensive rats anesthetized with urethane (1600 mg/kg of animal weight, intraperitoneally). It has been shown that in normotensive rats, injections of a specific inhibitor of Na+, K(+)-ATPase ouabain (10(-8)-10(-5) mol/l) in the populations of the neurons within nucleus of the solitary tract (NTS), paramedian reticular nucleus (PMn) and lateral reticular nucleus (LRN) were accompanied by the development of the hypertensive responses in a dose-dependent fashion. These data suggest that Na+, K(+)-ATPase of the neuron somatic membranes in the medullary cardiovascular nuclei is involved in neural control of the cardiovascular function, and its inhibition by microinjections of ouabain promotes the development of hypertension. In contrast to normotensive rats, ouabain injected in the medullary nuclei of spontaneously hypertensive animals induced either enhanced hypertensive or hypotensive responses. Biochemical analysis revealed that the activity of Na+, K(+)-ATPase in the microsomal fraction of the medulla oblongata of spontaneously hypertensive rats significantly exceeded its activity in the medulla oblongata of normotensive animals. Possible mechanisms of ouabain effects in spontaneously hypertensive rats have being discussed. Activation of Na+, K(+)-ATPase activity of the cardiovascular neurons with asparkam injections in the medullary nuclei resulted in hypotensive responses in both normotensive and spontaneously hypertensive rats.
Subject(s)
Hypertension/enzymology , Neurons/drug effects , Olivary Nucleus/drug effects , Reticular Formation/drug effects , Sodium-Potassium-Exchanging ATPase/metabolism , Solitary Nucleus/drug effects , Animals , Blood Pressure/drug effects , Cardiotonic Agents/administration & dosage , Enzyme Activation/drug effects , Hemodynamics/drug effects , Hypertension/physiopathology , Injections, Intraventricular , Microinjections , Neurons/enzymology , Olivary Nucleus/enzymology , Ouabain/administration & dosage , Potassium Magnesium Aspartate/administration & dosage , Potassium Magnesium Aspartate/analogs & derivatives , Rats , Rats, Inbred SHR , Reticular Formation/enzymology , Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors , Solitary Nucleus/enzymologyABSTRACT
It has been shown that Transfer factor (TF) to Staphilococcus aureus antigens blocked ATP-induced component of the inhibitory junction potential in taenia coli smooth muscle from guinea-pig, and converted an inhibitory action of exogenous ATP into an exciting one (instead of the hyperpolarization of the smooth muscle, TF induced its depolarization). TF at 10-6 mg/ml converted the relaxing effects of sodium nitroprusside (nitric oxide donor) into exciting ones in smooth muscle strips. Higher concentrations (10-5-10-3 mg/ml) of TF slightly amplified the relaxing effect of sodium nitroprusside. Both a- and b-adrenergic activation in taenia coli smooth muscle were not sensitive to that agent.
Subject(s)
Adenosine Triphosphate/pharmacology , Colon/drug effects , Muscle Contraction/drug effects , Muscle Relaxation/drug effects , Muscle, Smooth/drug effects , Transfer Factor/pharmacology , Animals , Colon/innervation , Colon/physiology , Guinea Pigs , Membrane Potentials/drug effects , Muscle Contraction/physiology , Muscle Relaxation/physiology , Muscle, Smooth/innervation , Muscle, Smooth/physiologyABSTRACT
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.
Subject(s)
Calcium/metabolism , Models, Biological , Muscle, Smooth/metabolism , Sarcomeres/metabolism , Adenosine Triphosphate/metabolism , KineticsABSTRACT
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.
Subject(s)
Calcium/physiology , Muscle, Smooth/physiology , Animals , Cecum/physiology , Guinea Pigs , In Vitro Techniques , Kinetics , Models, Biological , Muscle Contraction/physiology , Muscle Relaxation/physiologyABSTRACT
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.
