| Autor: |
Soloviev, Anatoly I., Tishkin, Sergey M., Zelensky, Sergey N., Ivanova, Irina V., Kizub, Igor V., Pavlova, Alexandra A., Moreland, Robert S. |
| Předmět: |
|
| Zdroj: |
American Journal of Physiology: Regulatory, Integrative & Comparative Physiology; Sep2005, Vol. 289, pR755-R762, 8p |
| Abstrakt: |
Radiation exposure increases vascular responsiveness, and this change involves endothelial damage, as well as direct effects on vascular smooth muscle. In this study, we tested the hypothesis that myofilament Ca2+ sensitivity in vascular smooth muscle is increased from single whole body gamma irradiation (6 Gy). We measured contractile responses from intact and permeabilized rat thoracic aortic rings combined with cytosolic Ca2+ ([Ca2+]i) measurements. The sensitivity to KCl and phenylephrine increased significantly in tissues from animals on the 9th and 30th clays postirradiation compared with control. Irradiation also significantly increased Ca2+ sensitivity in β-escin permeabilized smooth muscle on the 9th and 30th days postirradiation. Inhibitors of protein kinase C, chelerythrine, and staurosporine, had no effect on the pCa-tension curves in control permeabilized tissues but significantly decreased Ca2+ sensitivity in permeabilized tissues on the 9th and 30th days postirradiation. Phorbol dibutyrate (PDBu, 10-7 M) increased Ca2+ sensitivity in control skinned smooth muscle but was without effect in irradiated vascular rings. Simultaneous measurement of contractile force and [Ca2+]i showed that myofilament Ca2+ sensitivity defined as the ratio of force change to [Ca2+]i significantly increased following γ-irradiation. PDBu (10-6 M) stimulation of intact aorta produced a sustained contraction, while the increase in [Ca2+]i was transient. In irradiated tissues, PDBu-induced contractions were greater than those seen in control tissues but there was no elevation in [Ca2+]i. Taken together, these data strongly support the hypothesis that irradiation increases the sensitivity of vascular smooth muscle myofilaments to Ca2+ and this effect is dependent on activation of protein kinase C. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
