1995 Fiscal Year Final Research Report Summary
The study for the myogenic response and intracellular calcium level in resistance arterioles from hypertensive or cardiac failure rats.
| Project/Area Number |
06670752
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | Hyogo College of Medicine |
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Principal Investigator |
OHYANAGI Mitsumasa Hyogo College of Medicine, First department of Internal Medicine, Assistant professor, 医学部, 講師 (90131573)
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| Project Period (FY) |
1994 – 1995
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| Keywords | myogenic response / spontaneously hypertensive rat / voltage dependent calcium channel / intracellular free calcium ion |
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| Research Abstract |
The myogenic response of arterioles, which induce vascular resistance, may be involved in regulating the total peripheral resistance. To clarify whether myogenic response is involved in the development of hypertension, we evaluated the myogenic response of arterioles isolated from the cremaster muscle of spontaneously hypertensive rats (SHR) at a prehypertensive stage (4-5 weeks old) and at an early stage of hypertension (7-8 weeks old) as compared with age matched Wistar Kyoto rats (WKY) using an in vitro systems. The myogenic response of SHR aged 7-8 weeks (but not those aged 4-5 weeks) significantly exceeded that of WKY when intravascular pressure was increased by either 15 mmHg or 30 mmHg. In evaluating the sensitivity of the voltage dependent calcium channel (VDCC) by inducing contraciton with KCl, the EC_<50> of the concentration-response curve of KCl was significantly reduced in the 7-8 week-old, but not in the 4-5 week-old SHR vs. WKY.Measurement of intracellular levels of free calcium ([Ca^<2+>]i) in arterioles of the 7-8 week-old SHR and WKY loaded with a calcium-sensitive dye showed that, during the myogenic response, changes in [Ca^<2+>] i when the pessure was elevated by 15 mmHg tended to be greater in SHR ; the increase was significant when pressue was elevated by 30 mmHg. The inhibition of the myogenic response induced by nitrendipine at 30 mmHg was greater in SHR.The myogenic response and sensitivity of VDCC increased in SHR with the development of hypertension. Thus, the myogenic response was enhanced in SHR,and may be explained in part by an increase in sensitivity of the VDCC.
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