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Ca++ blockers and the release of Ca++ by cyclic GMP in visual rods
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Ca++ BLOCKERS AND THE RELEASE OF Ca++ BY cyclic GMP IN VISUAL RODS K.W.Koch & U.B.Kaupp Univ.Osnabrueck, Abteilung Biophysik, 45 Osnabrueck, FRG Ca* is released by cyclic GMP from disks of rods of the bovine retina. The Ca* release occurs rapidly (lo-20 set) at a high stoichiometry (10.000-15.000 Ca* ions/disk). The K value for cyclic GMPis 80 M. The amplitudes of the Cafe releame by cyclic GMP and 8-Br-cGMF are of similar magnitude; other analogues of cyclic GMP are ineffective. A Ca* gradient across the disk membrane is a necessary condition for the release to occur. If this Ca* gradient is dissipated by the ionophore A23187 no Cafe release is observed after addition of cyclic GMP. The Ca* release is inhibited by organic and inorganic Ca* blocking agents. L-cis-Diltiazem inhibits the release at micromolar concentrations; D-cis-Diltiazem is without effect. The sequence of efficiency to inhibit the cyclic GMP-stimulated Ca* release is: L-cis-Diltiazem > PN 205-033 > (+)Prenylamin > D-600 Nifedipine and Nimodi ine had no effect. The Ca* release is also inhibited by 5 p CdJ . The above results suggest that cyclic GMP regulates an ion transport system in the disk membrane but does not affect the redistribution between Ca* bound to the surface of the disk membrane and free Ca*.
2+ ATPase Al 2 PROPERTIESOF ANTIBODIESAGAINSTERYTtROCYTE Ca -TRANSPORT Joachim Kolandt and Klaus Gietzen, Department of Pharmacology and Toxicology, University of Ulm,2P-7900 Ulm, FRG. Antibodies against purified Ca -transport ATPase from human erythrocytes were raised in rabbits. Immunodiffusion experiments revealed that had been developed. The immunoglobulin fracprecipitating antibodies inhibited solely the calmodulin-dependent fraction of erythrocyte 99 Ca -transport ATPase activity whereas the basal (in the absence of added calmodulin) activity of the enzyme was not significantly affected by the antibodies. The antibodies produced similar dose-response curves for the calmodulin and the oleic acid-stimulated enzyme. However, the n lobulin fraction was considerably less effective in inhibiting The results ??-zanspcrt ATPase activated by limited proteolysis. obtained with our antibodies are compatible with the interp.retation that at least one subpopulation of the antibodies attack the enzyme at or close to the calmodulin binding site of s+heATPase. The antibodies inhibited as ~11 the calmodulin-regulated Ca -transport ATPase from smooth muscle plasma membrane, though with lower potency. Howporcine the immunoglobulig+ fraction failed to suppress porcine cardiac ever, sarcoplasmic reticulun Ca -transport ATPase activity in the investiIn addition the activity of phosphodigated concentration range. e&erase from rat brain, another enzyme modulated by calmodulin, was not at all effected by the immunoglobulin fraction. The antibodies open the attrac$$ve opportunity to isolate the calmodulin receptor of erythATPase by using the antibodies as affinity rocyte Ca -transport Furthermore they may be useful for quantification of the numligands. ber of ATPase molecules per cell. 288
Ca++ BLOCKERS AND THE RELEASE OF Ca++ BY cyclic GMP IN VISUAL RODS K.W.Koch & U.B.Kaupp Univ.Osnabrueck, Abteilung Biophysik, 45 Osnabrueck, FRG Ca* is released by cyclic GMP from disks of rods of the bovine retina. The Ca* release occurs rapidly (lo-20 set) at a high stoichiometry (10.000-15.000 Ca* ions/disk). The K value for cyclic GMPis 80 M. The amplitudes of the Cafe releame by cyclic GMP and 8-Br-cGMF are of similar magnitude; other analogues of cyclic GMP are ineffective. A Ca* gradient across the disk membrane is a necessary condition for the release to occur. If this Ca* gradient is dissipated by the ionophore A23187 no Cafe release is observed after addition of cyclic GMP. The Ca* release is inhibited by organic and inorganic Ca* blocking agents. L-cis-Diltiazem inhibits the release at micromolar concentrations; D-cis-Diltiazem is without effect. The sequence of efficiency to inhibit the cyclic GMP-stimulated Ca* release is: L-cis-Diltiazem > PN 205-033 > (+)Prenylamin > D-600 Nifedipine and Nimodi ine had no effect. The Ca* release is also inhibited by 5 p CdJ . The above results suggest that cyclic GMP regulates an ion transport system in the disk membrane but does not affect the redistribution between Ca* bound to the surface of the disk membrane and free Ca*.
2+ ATPase Al 2 PROPERTIESOF ANTIBODIESAGAINSTERYTtROCYTE Ca -TRANSPORT Joachim Kolandt and Klaus Gietzen, Department of Pharmacology and Toxicology, University of Ulm,2P-7900 Ulm, FRG. Antibodies against purified Ca -transport ATPase from human erythrocytes were raised in rabbits. Immunodiffusion experiments revealed that had been developed. The immunoglobulin fracprecipitating antibodies inhibited solely the calmodulin-dependent fraction of erythrocyte 99 Ca -transport ATPase activity whereas the basal (in the absence of added calmodulin) activity of the enzyme was not significantly affected by the antibodies. The antibodies produced similar dose-response curves for the calmodulin and the oleic acid-stimulated enzyme. However, the n lobulin fraction was considerably less effective in inhibiting The results ??-zanspcrt ATPase activated by limited proteolysis. obtained with our antibodies are compatible with the interp.retation that at least one subpopulation of the antibodies attack the enzyme at or close to the calmodulin binding site of s+heATPase. The antibodies inhibited as ~11 the calmodulin-regulated Ca -transport ATPase from smooth muscle plasma membrane, though with lower potency. Howporcine the immunoglobulig+ fraction failed to suppress porcine cardiac ever, sarcoplasmic reticulun Ca -transport ATPase activity in the investiIn addition the activity of phosphodigated concentration range. e&erase from rat brain, another enzyme modulated by calmodulin, was not at all effected by the immunoglobulin fraction. The antibodies open the attrac$$ve opportunity to isolate the calmodulin receptor of erythATPase by using the antibodies as affinity rocyte Ca -transport Furthermore they may be useful for quantification of the numligands. ber of ATPase molecules per cell. 288