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Altered local regulation of blood flow and shear rate in renal hypertension
D H Wang1, R L Prewitt, C K Reilly
1Department of Physiology, Eastern Virginia Medical School, Norfolk.
Insights
Hypertension impairs skeletal muscle blood flow regulation early on. Chronic high blood pressure may lead to impaired endothelial function and altered shear stress in the cremaster muscle.
Area of Science:
- Physiology
- Cardiovascular Research
- Hypertension Studies
Background:
- Hypertension is a complex condition affecting multiple organ systems.
- Skeletal muscle blood flow regulation is crucial for oxygen delivery and waste removal.
- Understanding autoregulation changes in hypertension is vital for managing complications.
Purpose of the Study:
- To assess acute and chronic blood flow autoregulation in the cremaster muscle of one-kidney, one-clip (1K1C) hypertensive rats.
- To investigate alterations in shear stress during hypertension development in this model.
Main Methods:
- Induction of hypertension using the one-kidney, one-clip (1K1C) model in rats.
- Measurement of mean blood pressure and heart rate.
- In vivo intravital microscopy to assess cremaster arteriolar dimensions.
- Dual-slit technique to measure cremaster muscle blood flow.
- Calculation of wall shear rate in the first-order arteriole (1A).
Main Results:
- 1K1C rats showed significantly increased mean blood pressure at 1 and 4 weeks.
- Cremaster muscle blood flow was reduced at 1 week but normalized by 4 weeks in 1K1C rats.
- Wall shear rate was not different at 1 week but significantly elevated at 4 weeks in 1K1C rats.
Conclusions:
- Skeletal muscle blood flow autoregulation is impaired in the acute phase of 1K1C hypertension.
- Elevated shear rate in chronic hypertension may indicate impaired endothelial function.
- This study provides insights into the vascular adaptations during hypertension development.
Abstract:
The purpose of this study was to evaluate acute and chronic autoregulation of blood flow in the cremaster muscle of one-kidney, one-clip (1K1C) hypertensive rats and to investigate alterations of shear stress during the development of hypertension. Unilateral renal artery stenosis and contralateral nephrectomy were performed in half of the rats and a sham operation was carried out in the other half. Mean blood pressure was significantly increased at 1 (38%) and 4 (34%) weeks in 1K1C rats v age-matched controls. Heart rate was significantly increased 15% at 1 week in 1K1C rats but returned to the control level at 4 weeks. Cremaster arteriolar dimensions were measured in vivo by intravital microscopy. Resting diameter of the first-order arteriole (1A) in 1K1C rats was decreased by 25% (P < .05) at 1 week and by 16% at 4 weeks (ns). Measured by the dual-slit technique, total blood flow to the cremaster muscle in 1K1C rats was reduced by 58% (P < .05) at 1 week but was not significantly different from control at 4 weeks. Wall shear rate calculated in the 1A of 1K1C rats was not significantly different from control at 1 week but was elevated 70% (P < .05) at 4 weeks. Therefore, autoregulation of blood flow in skeletal muscle is impaired and/or overridden in the acute phase of 1K1C hypertension. Shear rate, however, did not deviate from the control level until later, which might be the result of impaired function of the endothelium in chronic hypertension.