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Amiloride is a weak inhibitor of Na+/Ca2+ exchange in isolated plasma membrane vesicles prepared from GH3 rat anterior pituitary cells. However, substitution on either a terminal guanidino nitrogen atom or the 5-amino nitrogen atom can increase inhibitory potency ca. 100-fold (I50 approximately 10 microM). A structure-activity study indicates that defined(More)
Na+/Ca2+ exchange is inhibited in both guinea pig cardiac membrane vesicles and papillary muscles in a concentration-dependent fashion by several analogs of the pyrazine diuretic amiloride. Structure/activity studies based on transport measurements in vesicles prepared from guinea pig left ventricle indicate that hydrophobic substitutions at the terminal(More)
Dialyzed rat liver cytosol (105 000 X g supernatant), when added along with 2.5 mM glutathione, blocked malonaldehyde formation in the NADPH-microsomal lipid peroxidation system, thus protecting against lipid peroxidation. Preheating the cytosol for 10 min at 60 degrees C destroyed its protective ability. Ammonium sulfate fractionation and Sephadex G-100(More)
Specific, saturable, and reversible binding of verapamil has been demonstrated in crude cardiac sarcolemmal membranes. These receptors possess a Kd of approximately 50 nM for verapamil as determined by either equilibrium binding studies, competition binding analysis, or kinetic analysis of on and off rates and display an average density of 1.25 pmol/mg of(More)
A semi-isolated cockroach heart preparation was used to rapidly determine the activity of cobra cardiotoxin, monitored as a direct response on heart rate. This preparation produced a dose-response curve in the presence of active cardiotoxin and demonstrated that cardiotoxin retained its biological activity after boiling, although cardiotoxin activity was(More)
GH3 rat anterior pituitary cells possess a Na+/Ca2+ exchange transport mechanism which is present in purified plasma membrane vesicles prepared from these cells. Imposition of an outwardly directed Na+ gradient in vesicles results in a marked concentrative uptake of Ca2+ which is abolished by the Ca2+ ionophore A23187. Transport activity depends on a(More)
The pharmacological activity of rigid analogues of 1,4-dihydropyridine calcium entry antagonists 9-16 is demonstrated by dose-dependent inhibition of the calcium contraction in depolarized rat aortic strips and by a [3H]nitrendipine binding assay in using cardiac sarcolemmal membranes. From the results, a model is proposed as the receptor-bound conformation(More)
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