ABSTRACT
Extracellular adenosine and adenosine triphosphate (ATP) are involved in biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, signal transduction and secretion in a variety of cell types. They are released from the cytoplasm of several cell types and interact with specific purinergic receptors which are present on the surface of many cells. This review summarizes the evidence on the potential value and applicability of ATP (not restricted to ATP-MgCl(2)) and adenosine in the field of anaesthesia and intensive care medicine. It focuses, in particular, on evidence and roles in treatment of acute and chronic pain and in sepsis. Based on the evidence from animal and clinical studies performed during the last 20 years, ATP could provide a valuable addition to the therapeutic options in anaesthesia and intensive care medicine. It may have particular roles in pain management, modulation of haemodynamics and treatment of shock.
Subject(s)
Adenosine Triphosphate/therapeutic use , Adenosine/therapeutic use , Anesthesia/methods , Critical Care/methods , Hemodynamics/drug effects , Humans , Pain/drug therapy , Shock, Septic/drug therapyABSTRACT
In this review the lyophilization of biotechnology products is discussed. It is emphasized that the final quality of a protein product is determined by an interplay between the proper choice of excipients and the freeze-drying process. A crystalline matrix after freeze-drying is detrimental for the protein product. A glassy amorphous state is a prerequisite for stability, however a glassy state as such will not assure sufficient stability. The glass temperature which defines the state of the freeze-dried cake can be influenced by the moisture content and the choice of excipients.
Subject(s)
Freeze Drying/standards , Recombinant Proteins , Biotechnology/standards , Drug Storage , Quality Control , Recombinant Proteins/chemistry , Recombinant Proteins/standardsABSTRACT
Gastric (H+ + K+)-ATPase was reconstituted into artificial phosphatidylcholine/cholesterol vesicles by means of a freeze-thaw-sonication procedure. The passive and active transport mediated by these vesicles were measured (Skrabanja, A.T.P., Asty, P., Soumarmon, A., De Pont, J.J.H.H.M. and Lewin, M.J.M. (1986) Biochim. Biophys. Acta 860, 131-136). To determine real initial velocities, the proteoliposomes were separated from non-incorporated enzyme, by means of centrifugation on a sucrose gradient. The purified proteoliposomes were used to measure active H+ and Rb+ transport, giving at room-temperature velocities of 46.3 and 42.5 mumol per mg per h, respectively. A transport ratio of two cations per ATP hydrolyzed was also measured. These figures indicate that the enzyme catalyzes an electroneutral H+-Rb+ exchange.
Subject(s)
Adenosine Triphosphatases/metabolism , Gastric Mucosa/enzymology , Liposomes/metabolism , Adenosine Triphosphate/metabolism , Animals , Biological Transport, Active/drug effects , Centrifugation, Density Gradient , Cholic Acid , Cholic Acids/pharmacology , H(+)-K(+)-Exchanging ATPase , Hydrogen-Ion Concentration , Protons , Rubidium/metabolism , Swine , Vanadates/pharmacologyABSTRACT
Gastric (H+ + K+)-ATPase was reconstituted into artificial phosphatidylcholine/cholesterol liposomes by means of a freeze-thaw-sonication technique. Upon addition of MgATP, active H+ transport was observed, with a maximal rate of 2.1 mumol X mg-1 X min-1, requiring the presence of 100 mM K+ at the intravesicular site. However, in the absence of ATP an H+-K+ exchange with a maximal rate of 0.12 mumol X mg-1 X min-1 was measured, which could be inhibited by the well-known ATPase inhibitors vanadate and omeprazole, giving the first evidence of a passive K+-H+ exchange function of gastric (H+ + K+)-ATPase. An Na+-H+ exchange activity was also measured, which was fully inhibited by 1 mM amiloride. Simultaneous reconstitution of Na+/H+ antiport and (H+ + K+)-ATPase could explain why reconstituted ATPase appeared less cation-specific than the native enzyme (Rabon, E.C., Gunther, R.B., Soumarmon, A., Bassilian, B., Lewin, M.J.M. and Sachs, G. (1985) J. Biol. Chem. 260, 10200-10212).
Subject(s)
Adenosine Triphosphatases/metabolism , Animals , Benzimidazoles/pharmacology , Biological Transport, Active/drug effects , Cell Membrane Permeability , H(+)-K(+)-Exchanging ATPase , Hydrogen-Ion Concentration , Kinetics , Liposomes , Membrane Potentials , Omeprazole , Potassium/metabolism , Protons , Swine , Vanadium/pharmacologyABSTRACT
Various values have been reported for the H+/ATP transport ratio of the (K+ + H+)-ATPase of the gastric parietal cell: 4, 2 and 1. We have, therefore, reinvestigated this matter with a vesicle preparation isolated from pig gastric mucosa. The vesicles are suspended in glycylglycine buffer (pH 6.11) at 22 degrees C, and incubated until equalization of the K+ concentration inside and outside (75 mM). After addition of ATP, the initial rates of H+ uptake and ATP hydrolysis are then measured. Proton uptake is inhibited in the absence of K+ or in the presence of nigericin. The K0.5 value for proton transport is 154 microM and the Km value for ATP hydrolysis is 61 microM. The Lineweaver-Burk plot for ATP hydrolysis vs. ATP concentration is linear with a Vmax of 5.5 nmol/mg protein per s, but that for H+ uptake is not. Thus with increasing ATP concentration (6.7 to 1670 microM) the transport ratio increases from 0.3 to 1.8. Extrapolation to infinite ATP concentration gives a value of 1.89. (S.E. 0.13, N = 5) and a Hill coefficient of n = 1.21 (S.E. 0.06, N = 5) implying that the true transport ratio is 2 H+/ATP with positive cooperativity between the protons.
