Activation of L-type Ca2+ currents in cardiac myocytes by photoreleased GTP
| Autor: | V. W. Twist, R. Z. Kozlowski, Trevor Powell, L. J. Goodstadt |
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| Rok vydání: | 1992 |
| Předmět: |
Agonist
GTP' medicine.drug_class Ultraviolet Rays Guinea Pigs In Vitro Techniques General Biochemistry Genetics and Molecular Biology GTP-binding protein regulators GTP-Binding Proteins medicine Animals Patch clamp General Environmental Science Membrane potential Photolysis General Immunology and Microbiology Voltage-dependent calcium channel Chemistry Myocardium General Medicine Protein kinase inhibitor Thionucleotides Kinetics Biochemistry Biophysics Calcium Channels Guanosine Triphosphate General Agricultural and Biological Sciences Intracellular |
| Zdroj: | Proceedings. Biological sciences. 250(1327) |
| ISSN: | 0962-8452 |
| Popis: | L-type calcium currents (ICa) were recorded from isolated ventricular myocytes by using standard patch-clamp methods. In the absence of agonist, photorelease of GTP by flash photolysis of intracellularly applied caged-GTP rapidly increased the amplitude of ICa over a wide range of membrane potentials. Control experiments clearly demonstrated that this effect was not due to either the release of photolytic by-products or to the light flash itself. The timecourse for activation of ICa by photolysis of caged-GTP was markedly altered by intracellular application of either GDP beta S or GTP gamma S. Upon maximal stimulation of ICa by intracellular dialysis with cAMP, photoreleased GTP induced a small, rapid increase in ICa followed by a gradual inhibition. The presence of Rp-cAMPS intracellularly reduced both the magnitude of the response to photoreleased GTP and its time to peak. Similar effects were observed when protein kinase inhibitor dialysed the cell interior, suggesting that both cAMP-dependent and independent processes were involved in this effect. We conclude that rapid release of GTP within ventricular myocytes, in the absence of agonist, causes rapid activation of L-type Ca2+ current. Mechanisms underlying this effect include stimulation of adenylate cyclase, together with other, as yet uncharacterized, GTP-dependent pathways for increasing ICa in the heart. |
| Databáze: | OpenAIRE |
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