본태성 고혈압쥐에서 Myogenic Tone의 변화:RhoA 단백질 및 Protein Kinase C의 역할

서정필,류성경,강나영,안덕선,이영호 대한순환기학회 2002 Korean Circulation Journal Vol.32 No.3

[$Ca^{2+}$ Sensitization Mechanism in Stretch-induced Myogenic Tone

Kim, Jung-Sup,Ryu, Sung-Kyung,Ahn, Duck-Sun,Kang, Bok-Soon,Lee, Young-Ho The Korean Society of Pharmacology 2002 The Korean Journal of Physiology & Pharmacology Vol.6 No.1

It has been suggested that $Ca^{2+}$ sensitization mechanisms might contribute to myogenic tone, however, specific mechanisms have not yet been fully identified. Therefore, we investigated the role of protein kinase C (PKC)- or RhoA-induced $Ca^{2+}$ sensitization in myogenic tone of the rabbit basilar vessel. Myogenic tone was developed by stretch of rabbit basilar artery. Fura-2 $Ca^{2+}$ signals, contractile responses, PKC immunoblots, translocation of PKC and RhoA, and phosphorylation of myosin light chains were measured. Stretch of the resting vessel evoked a myogenic contraction and an increase in the intracellular $Ca^{2+}$ concentration $([Ca^{2+}]_i)$ only in the presence of extracellular $Ca^{2+}$. Stretch evoked greater contraction than high $K^+$ at a given $[Ca^{2+}]_i.$ The stretch-induced increase in $[Ca^{2+}]_i$ and contractile force were inhibited by treatment of the tissue with nifedipine, a blocker of voltage-dependent $Ca^{2+}$ channel, but not with gadolinium, a blocker of stretch-activated cation channels. The PKC inhibitors, H-7 and calphostin C, and a RhoA-activated protein kinase (ROK) inhibitor, Y-27632, inhibited the stretch-induced myogenic tone without changing $[Ca^{2+}]_i.$ Immunoblotting using isoform-specific antibodies showed the presence of $PKC_{\alpha}$ and $PKC_{\varepsilon}$ in the rabbit basilar artery. $PKC_{\alpha},$ but not $PKC_{\varepsilon},$ and RhoA were translocated from the cytosol to the cell membrane by stretch. Phosphorylation of the myosin light chains was increased by stretch and the increased phosphorylation was blocked by treatment of the tissue with H-7 and Y-27632, respectively. Our results are consistent with important roles for PKC and RhoA in the generation of myogenic tone. Furthermore, enhanced phosphorylation of the myosin light chains by activation of $PKC_{\alpha}$ and/or RhoA may be key mechanisms for the $Ca^{2+}$ sensitization associated with myogenic tone in basilar vessels.

Ca<SUP>2⁢</SUP> Sensitization Mechanism in Stretch-induced Myogenic Tone

Jung-Sup Kim,Sung-Kyung Ryu,Duck-Sun Ahn,Bok-Soon Kang,Young-Ho Lee 대한생리학회-대한약리학회 2002 The Korean Journal of Physiology & Pharmacology Vol.6 No.1

<P> It has been suggested that Ca<SUP>2⁢</SUP> sensitization mechanisms might contribute to myogenic tone, however, specific mechanisms have not yet been fully identified. Therefore, we investigated the role of protein kinase C (PKC)- or RhoA-induced Ca<SUP>2⁢</SUP> sensitization in myogenic tone of the rabbit basilar vessel. Myogenic tone was developed by stretch of rabbit basilar artery. Fura-2 Ca<SUP>2⁢</SUP> signals, contractile responses, PKC immunoblots, translocation of PKC and RhoA, and phosphorylation of myosin light chains were measured. Stretch of the resting vessel evoked a myogenic contraction and an increase in the intracellular Ca<SUP>2⁢</SUP> concentration ([Ca<SUP>2⁢</SUP>]<SUB>i</SUB>) only in the presence of extracellular Ca<SUP>2⁢</SUP>. Stretch evoked greater contraction than high K<SUP>⁢</SUP> at a given [Ca<SUP>2⁢</SUP>]<SUB>i</SUB>. The stretch-induced increase in [Ca<SUP>2⁢</SUP>]<SUB>i</SUB> and contractile force were inhibited by treatment of the tissue with nifedipine, a blocker of voltage-dependent Ca<SUP>2⁢</SUP> channel, but not with gadolinium, a blocker of stretch-activated cation channels. The PKC inhibitors, H-7 and calphostin C, and a RhoA-activated protein kinase (ROK) inhibitor, Y-27632, inhibited the stretch-induced myogenic tone without changing [Ca<SUP>2⁢</SUP>]<SUB>i</SUB>. Immunoblotting using isoform-specific antibodies showed the presence of PKCα and PKCε in the rabbit basilar artery. PKCα, but not PKCε, and RhoA were translocated from the cytosol to the cell membrane by stretch. Phosphorylation of the myosin light chains was increased by stretch and the increased phosphorylation was blocked by treatment of the tissue with H-7 and Y-27632, respectively. Our results are consistent with important roles for PKC and RhoA in the generation of myogenic tone. Furthermore, enhanced phosphorylation of the myosin light chains by activation of PKCα and/or RhoA may be key mechanisms for the Ca<SUP>2⁢</SUP> sensitization associated with myogenic tone in basilar vessels.

Enhanced Stretch-Induced Myogenic Tone in the Basilar Artery of Spontaneously Hypertensive Rats

Ahn, Duck-Sun,Choi, Soo-Kyoung,Kim, Young-Hwan,Cho, Young-Eun,Shin, Heung Mook,Morgan, Kathleen G.,Lee, Young-Ho S. Karger 2007 Journal of vascular research Vol.44 No.3

<P>We investigated if the magnitude of myogenic tone in the basilar artery of SHR differs from that in WKY and, if so, whether RhoA- or PKC-dependent mechanisms were involved. Myogenic tone was developed in response to stretch. Stretch-induced myogenic contraction was significantly greater in the SHR than WKY in the presence of external Ca<SUP>2+</SUP>. However, in the absence of external Ca<SUP>2+</SUP>, stretch did not evoke a myogenic tone. The [Ca<SUP>2+</SUP>]<SUB>i</SUB>-induced contraction was larger in SHR than WKY and the [Ca<SUP>2+</SUP>]<SUB>i</SUB>-force curve was significantly shifted to the left in SHR compared to WKY. Y-27632 significantly inhibited stretch-induced myogenic tone, but the inhibitory effect was larger in the SHR than WKY. However, PKC inhibitors had no significant effect on the myogenic tone. RhoA and PKCε were expressed at higher levels in the SHR compared to the WKY. RhoA and PKCα translocated from the cytosol to the cell membrane in response to stretch in both animals, but PKCε was translocated only in SHR. Our results strongly suggest that stretch-induced myogenic tone is enhanced in SHR, and the activation of RhoA/Rho kinase plays an important role in the enhanced myogenic tone in SHR.</P><P>Copyright © 2007 S. Karger AG, Basel</P>

500 Hz-tone Burst 자극음을 이용한 전정유발 근전위

배우용,황찬호,허승덕,이태훈,장윤석,안중기,이현직,김재룡 대한이비인후과학회 2006 대한이비인후과학회지 두경부외과학 Vol.49 No.2

Background and Objectives:Vestibular evoked myogenic potential (VEMP) is muscle reflex caused by surface electrodes following repeated high-intensity auditory stimulation. The current study attempted to determine whether VEMP can be consistently evoked from the sternocleidomastoid muscle (SCM) by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst. Subjects and Method:Air-conducted and bone-conducted VEMPs in response to 500 Hz-tone burst were recorded from the SCM of 13 normal volunteers. Subjects were seated on their chairs and made to hold their heads turned up as far as possible towards the side, contralateral to the stimulated ear voluntarily. Two different sound durations (rise/fall time=2 msec, plateau time=2 msec[2/2] and rise/fall time=5 msec, plateau time=5 msec[5/5]) were presented through a insertphone or bone vibrators. Latencies and amplitudes of p13 and n23 responses were measured. Results:All normal volunteers showed p13-n23 responses to 50 dB bone-conducted tone burst as well as to 100 dB air-conducted tone burst. The values of latency of p13 and n23 were the most reliable at 5/5 air-conducted in evaluation by coefficiency of variance. Mean p13 and N23 latencies by airconducted tone burst were significantly longer than those of bone-conducted. Mean p13-n23 amplitudes by air-conducted tone burst were significantly larger than those by bone-conducted at 2/2 sound duration. Conclusion:VEMP could be consis-tently evoked by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst, especially at 5/5 air-conducted. (Korean J Otolaryngol 2006;49:143-7)