In vivo apparent peptide-receptor dissociation rate constants for arginine vasopressin analogs estimated from inhibition of rat pressor responses

1987 ◽  
Vol 65 (10) ◽  
pp. 2099-2103
Author(s):  
Diana Gazis
Keyword(s):  
Blood Pressure ◽  
Arginine Vasopressin ◽  
Rate Constants ◽  
Dissociation Rate ◽  
Arginine Vasotocin ◽  
Moderate Dose ◽  
Peptide Receptor ◽  
Pressor Responses ◽  
Dissociation Rate Constants

Apparent pressor receptor dissociation rate constants for arginine vasopressin, arginine vasotocin, oxytocin, oxypressin, and [1-deamino, 9-D-alanineamide]arginine vasopressin were estimated by the following method. Two minutes after injection of a moderate dose of agonist into urethane-anesthetized rats prepared for recording mean blood pressure, a large dose of inhibitor was injected. Under these conditions, in the first few moments after inhibitor injection, there should be no rebinding of the agonist after it dissociates, because vacant receptors should be immediately occupied by inhibitor. The rate of the blood pressure drop at the initiation of inhibition was calculated and used as an estimate of the dissociation rate of the agaonist. Apparent dissociation rate constants thus estimated were 1.1, 1.1, 6.9, 5.8, and 13.9 min−1 for arginine vasopressin, arginine vasotocin, oxytocin, oxypressin, and [1-deamino, 9-D-alanineamide]arginine vasopressin, respectively. These rate constants were inversely related to the pressor potencies (435, 250, 5, 3, and 0.7 U/mg, respectively) of these five compounds. Such a relationship is to be expected if decreased potency is in part due to a faster "off" rate from pressor receptors.

Oxygen affinity and amino acid sequence of myoglobins from endothermic and ectothermic fish

2001 ◽  
Vol 280 (4) ◽  
pp. R1123-R1133 ◽  
Author(s):  
David J. Marcinek ◽  
Joseph Bonaventura ◽  
Jonathan B. Wittenberg ◽  
Barbara A. Block
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Rate Constants ◽  
Oxygen Affinity ◽  
Dissociation Rate ◽  
Low Oxygen ◽  
Dissociation Kinetics ◽  
Oxygen Dissociation ◽  
Dissociation Rate Constants

Myoglobin (Mb) buffers intracellular O2 and facilitates diffusion of O2 through the cell. These functions of Mb will be most effective when intracellular Po 2 is near the partial pressure of oxygen at which Mb is half saturated (P50) of the molecule. We test the hypothesis that Mb oxygen affinity has evolved such that it is conserved when adjusted for body temperature among closely related animals. We measure oxygen P50s tonometrically and oxygen dissociation rate constants with stopped flow and generate amino acid sequence from cDNA of Mbs from fish with different body temperatures. P50s for the endothermic bluefin tuna, skipjack tuna, and blue marlin at 20°C were 0.62 ± 0.02, 0.59 ± 0.01, 0.58 ± 0.04 mmHg, respectively, and were significantly lower than those for ectothermic bonito (1.03 ± 0.07 mmHg) and mackerel (1.39 ± 0.03 mmHg). Because the oxygen affinity of Mb decreases with increasing temperature, the above differences in oxygen affinity between endothermic and ectothermic fish are reduced when adjusted for the in vivo muscle temperature of the animal. Oxygen dissociation rate constants at 20°C for the endothermic species ranged from 34.1 to 49.3 s−1, whereas those for mackerel and bonito were 102 and 62 s−1, respectively. Correlated with the low oxygen affinity and fast dissociation kinetics of mackerel Mb is a substitution of alanine for proline that would likely result in a more flexible mackerel protein.

In vivo simultaneous comparison of pressor and uterine responses to a single agonist (oxypressin) in estrous rats

1987 ◽  
Vol 65 (1) ◽  
pp. 6-11
Author(s):  
Diana Gazis ◽  
Geneviève Gonzalez ◽  
Milton Mendlowitz
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Response ◽  
Pressor Response ◽  
Dissociation Rate ◽  
Peptide Receptor ◽  
Uterine Contractions ◽  
Receptor Compartment ◽  
Muscle Types ◽  
Simultaneous Comparison

To try to compare receptor compartment kinetics, receptor binding, and binding–response coupling for two smooth muscle types in vivo, pressor and uterine responses to oxypressin, an equipotent analog of oxytocin and vasopressin, were studied simultaneously in urethane-anesthetized, pentolinium–indomethacin treated rats. Access of peptide to the pressor and uterine receptor compartments and peptide–receptor dissociation rate had a negligible effect on the two responses. During both injections and infusions, the blood pressure response seemed to be determined largely by plasma levels of oxypressin. The uterine response to oxypressin, however, was paradoxical. The heights of individual uterine contractions seemed to be determined throughout by plasma oxypressin concentrations. The interval between contractions also seemed to be determined by plasma peptide concentrations during injections. However, as plasma peptide increased and reached steady state during infusion, contraction interval behaved as if plasma peptide concentrations were decreasing. This effect was more marked at the beginning of infusion. The implication of these results is that binding determines the pressor response to oxypressin and binding–response coupling does not change. In contrast, although binding determines the uterine response to oxypressin during injection and binding–response coupling appears constant, some factor in addition to binding affects the contraction interval portion of the uterine response and modifies the apparent binding–response coupling of this parameter during infusion.

scholarly journals NAD(P)H: FMN-oxidoreductase functioning under macromolecular crowding: in vitro modeling

2019 ◽  
Vol 486 (4) ◽  
pp. 500-503
Author(s):  
A. E. Govorun ◽  
E. N. Esimbekova ◽  
V. A. Kratasyuk
Keyword(s):  
Rate Constants ◽  
Vibrio Fischeri ◽  
Macromolecular Crowding ◽  
Dissociation Rate ◽  
Common Belief ◽  
Native Conformation ◽  
The Common ◽  
Dissociation Rate Constants

The functioning of Vibrio fischeri NAD(P)H: FMN-oxidoreductase (Red) under conditions of macromolecular crowding (MMC) modeled in vitro by adding biopolymers (starch and gelatin) was studied. The dissociation rate constants and the activation energies of dissociation of Red to the subunits were calculated; the process of denaturation of Red was analyzed. It was shown that the functioning of Red both under conditions of MMC and diluted solutions is the same. The result refutes the common belief that due to MMC the stabilization of enzymes’ native conformation occurs in vivo when compared to in vitro.

scholarly journals Dissociation Rate Constants of Human Fibronectin Binding to Fibronectin-binding Proteins on LivingStaphylococcus aureusIsolated from Clinical Patients

2012 ◽  
Vol 287 (9) ◽  
pp. 6693-6701 ◽  
Author(s):  
Nadia N. Casillas-Ituarte ◽  
Brian H. Lower ◽  
Supaporn Lamlertthon ◽  
Vance G. Fowler ◽  
Steven K. Lower
Keyword(s):  
Rate Constants ◽  
Binding Proteins ◽  
Dissociation Rate ◽  
Human Fibronectin ◽  
Fibronectin Binding ◽  
Dissociation Rate Constants

scholarly journals Head-to-tail polymerization of microtubules in vitro. Electron microscope analysis of seeded assembly.

1980 ◽  
Vol 84 (1) ◽  
pp. 141-150 ◽  
Author(s):  
L G Bergen ◽  
G G Borisy
Keyword(s):  
Electron Microscope ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Dissociation Rate ◽  
Association Constants ◽  
Directional Growth ◽  
Microtubule Protein ◽  
Electron Microscope Analysis ◽  
Dissociation Rate Constants

Microtubules are polar structures, and this polarity is reflected in their biased directional growth. Following a convention established previously (G. G. Borisy, 1978, J. Mol. Biol. 124:565--570), we define the plus (+) and minus (-) ends of a microtubule as those equivalent in structural orientation to the distal and proximal ends, respectively, of the A subfiber of flagellar outer doublets. Rates of elongation were obtained for both ends using flagellar axonemes as seeds and porcine brain microtubule protein as subunits. Since the two ends of a flagellar seed are distinguishable morphologically, elongation of each end may be analyzed separately. By plotting rates of elongation at various concentrations of subunit protein, we have determined the association and dissociation rate constants for the plus and minus ends. Under our conditions at 30 degrees C, the association constants were 7.2 X 10(6) M-1 s-1 and 2.25 X 10(6) M-1 s-1 for the plus and minus ends, respectively, and the dissociation constants were 17 s-1 and 7 s-1. From these values and Wegner's equations (1976, J. Mol. Biol. 108:139--150), we identified the plus end of the microtubule as its head and calculated "s," the head-to-tail polymerization parameter. Surprisingly small values (s = 0.07 +/- 0.02) were found. The validity of models of mitosis based upon head-to-tail polymerization (Margolis et al., 1978, Nature (Lond.) 272:450--452) are discussed in light of a small value for s.

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