Venom of the scorpion Leiurus quinquestriatus acts cooperatively with the alkaloids veratridine, aconitine, and batrachotoxin in activating the action potential Na+ ionophore. A small (Mr = 6700), basic (pI approximately 9.8), toxic polypeptide purified approximately 80-fold from this venom by ion exchange chromatography appears homogeneous by gel electrophoresis and isoelectric focusing and, l...

We compared the slopes of the EMF responses and the response range of a solid contact electrode based on a tribenzylamine ionophore with those based on a tris(2-phenylethyl)amine ionophore and a tris(3-phenylpropyl)amine ionophore. Their slopes of the EMF responses showed, respectively, 57.7, 58.1, 59.0 mV pH(-1) (at 20 +/- 0.2 degrees C). Also, the linear pH response dynamic ranges were 2.74-1...

PURPOSE Experiments were conducted to examine how elevation of calcium in the lens impairs the lens sodium pump. METHODS Rabbit lenses were incubated in the presence or absence of calcium ionophore A23187. 86Rb uptake by the intact lens was measured as an index of sodium pump activity. Na,K-ATPase (ouabain-sensitive adenosine triphosphate [ATP] hydrolysis) activity was determined in membrane ...

We investigated the pathways for low density lipoprotein (LDL) transport across an endothelial barrier in individually perfused microvessels before and after an increase in permeability. The divalent cation ionophore A23187 (5 microM) was used to increase microvessel permeability. LDL permeability coefficients (PsLDL) were measured using quantitative fluorescence microscopy. In the control stat...

Tissue factor (TF) procoagulant activity (PCA) on the surface of intact HL-60 cells is encrypted. This latent TF PCA was activated by exposing the cells to ionomycin, a calcium ionophore. Within seconds an increase in TF PCA of greater than 100-fold was observed. The ionomycin effect was blocked by pretreating the cells with calmidazolium, a calmodulin inhibitor. Changes in TF structure and fun...

The effects of the ionophore X-537A on mechanical function and on ionic exchange were studied in the isolated, arterially perfused rabbit interventricular septum. X-537A produced an initial positive inotropic response which was, however, transient in this preparation and appeared to be dependent on an effect of the ionophore on catecholamines. The positive inotropy gave way to a progressive dec...

The extracellular matrix (ECM) protein thrombospondin (TSP) binds specifically to polymorphonuclear leucocyte (PMN) surface receptors and promotes cell adhesion and motility. TSP receptor expression increases 30-fold after activation with the synthetic chemotactic peptide, N-formylmethionyl-leucylphenylalanine (FMLP) or the Ca2+ ionophore A23187, in combination with cytochalasin B. The expressi...