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The molecular mode of action of the Ca agonist (−) BAY K 8644 on the cardiac Ca channel (1993)

Bechem, M. ; Hoffmann, H.

Springer

Pflügers Archiv 424 (1993), S. 343-353

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ISSN: 1432-2013

Keywords: Ca channel ; (−) BAY K 8644 ; Ca agonists ; Cardiac cells ; Ca current ; Mode of action ; Dihydropyridine receptor

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract The primary drug action of (−) BAY K 8644 on whole-cell Ca current in atrial myocytes was measured under conditions where secondary Ca-mediated changes of Ca channel activity were minimized. The most direct action of (−) BAY K 8644 is the change of gating kinetics which results in a strictly voltage-dependent increase of the peak current in the voltage range between −40 and 0 mV. Peak currents were increased dose dependently in the concentration range from 1 to 30 nM. Analysis of peak current/voltage relations revealed a linear shift of the current activation by approximately 23 mV to more negative membrane potentials, without any change in its voltage dependence and in the current reversal potential or the maximum whole-cell conductance. Measurement of Ca current activation and deactivation time constants suggests that (−) BAY K 8644 prolongs the single-channel open time without affecting the closed time. From the shift of the open time function to more negative voltages by about 50 mV the energy transferred to the gating process is calculated to be 5.4 kJ/mol (1.3 kcal/mol). The drug-induced slow component of tail current has been used to estimate the true dose/response relation for (−) BAY K 8644. A K D value of 4.3 nM and a Hill coefficient of 1.25 were determined. Flash-induced competition experiments with the Ca antagonist nifedipine allowed the measurement of binding kinetics of (−) BAY K 8644. The association rate constant is estimated to about 5×106 mol−1 · s−1 and dissociation time constant is approximately 50–70 s; both are in close agreement with receptor binding studies. Results are discussed in relation to models for drug action of dihydropyridine-type compounds and to implications for the structure of the Ca channel protein.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00384362

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1,4-Diazabuta-1,3-dien-N-Sulfinylamin-Nickel(0)-Komplexe (1994)

Wenschuh, E. ; Hoffmann, H. ; Zimmering, R. ; [et al.]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 620 (1994), S. 926-930

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ISSN: 0044-2313

Keywords: Nickel(0) complexes ; 1,4-diazabuta-1,3-diene ; N-sulfinylamine ligands ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: 1,4-Diazabuta-1,3-Diene-N-Sulfinylamin Nickel(0) ComplexesSynthesis, properties, and reactions of 1,4-diazabuta-1,3-diene-N-sulfinylamine nickel(0) complexes are described. The highly coloured and extremely air and moisture sensitive nickel(0) complexes have been characterized by means of i.r. and 1H n.m.r.spectroscopy. The N-sulfinylamine ligands are η2-(S,N)-side on coordinated.

Notes: Synthese, Eigenschaften und Reaktionen von 1,4-Diazabuta-1,3-dien-N-sulfinylamin-nickel(0)-Komplexen des Typs Ni(DAB)(RNSO) (R = Ph, p-Tol, Cy) werden beschrieben. Die Charakterisierung der diamagnetischen, intensiv farbigen und extrem oxidations- und feuchtigkeitsempfindlichen Nickel(0)-Komplexe erfolgte mit Hilfe der IR- und 1H-NMR-Spektroskopie. Die N-Sulfinylamin-Liganden sind η2-(S,N)-side on koordiniert.

Additional Material: 2 Ill.