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Biomedical subjects

F Brunner

Publications and source records attributed to F Brunner.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Thermodynamic study of iodocyanopindolol beta-adrenoceptors interactions with rat lung and cerebral cortex.

(+/-)125 I-cyanopindolol ((+/-) I CYP) was used to characterize beta-adrenoceptors on rat lung and cerebral cortex membranes. The affinity of (+/-) ICYP was higher for lung (Kd = 64.3 pM) at 37 degrees C. The association reaction of (+/-) ICYP was faster with lung (k+1 = 1.52 X 10(9) M-1.min-1) than with cerebral cortex beta-adrenoceptors (k+1 = 1.75 X 10(8) M-1.min-1). In both tissues, the dissociation reaction followed a biphasic process with a fast (t 1/2 = 15.4 min and 5.6 min for lung and cerebral cortex respectively) and a slow component (t 1/2 = 474 min and 255 min for lung and cerebral cortex respectively). The thermodynamic parameters for (+/-) ICYP - beta-adrenoceptors binding have been determined from kinetics and equilibrium studies, for the two tissues, at several temperatures between 0 degrees and 44 degrees C. For lung and cerebral cortex, Arrhenius plots were linear with different energies of activation. Van't Hoff plot was not linear for lung and the standard enthalpy and entropy changes of (+/-) ICYP - beta-adrenoceptors interaction decreased linearly with temperature: the binding occurred with a negative heat capacity change (delta Cp degrees = -368.9 cal. moles-1.K-1) at 25 degrees C. Thermodynamic and kinetic results show that binding of (+/-) ICYP to lung beta-adrenoceptors could involve two successive equilibria with a conformational change of the beta-adrenergic receptor.

Animals↗
PubMedDate not supplied

Muscarinic receptors of the vascular bed: radioligand binding studies on bovine splenic veins.

Despite an obvious lack of parasympathetic innervation to the spleen, pharmacological evidence suggests the presence of cholinergic receptors in isolated bovine splenic veins. We therefore studied muscarinic cholinergic binding sites in a bovine splenic vein preparation by direct radioligand binding techniques using [3H]quinuclidinyl benzilate ([3H]QNB) as radioactive probe. Saturation experiments indicated one homogeneous class of high-affinity binding sites, with a KD of 0.11 nM and a binding site density Bmax of 55 fmol/mg protein. The rate constants at 37 degrees C for formation and dissociation of the [3H]QNB receptor complex were 2.7 X 10(9) M-1 h-1 and 0.38 h-1, respectively, yielding a KD of 0.14 nM. The binding sites showed a high stereospecificity, which was evident from competition experiments with dexetimide (KI = 1.3 nM) and levetimide (KI = 4.6 microM). In competition experiments with muscarinic and nicotinic antagonists and some antidepressants, only one binding site was found, whereas with muscarinic agonists, two binding sites were detected. In the presence of 0.1 mM guanyl-imido-diphosphate, only one binding site could be identified with the muscarinic agonist carbamylcholine. The affinity of [3H]QNB, on the other hand, was slightly decreased, and Bmax values were unchanged. It is concluded that specific, saturable, high-affinity muscarinic binding sites in the bovine splenic vein have been identified and characterized that exhibit properties similar to cholinergic receptors of brain and peripheral tissues and probably mediate acetylcholine-induced relaxation of splenic veins.

Animals↗