Abstract
The myogenic response of middle cerebral arteries (MCA) protects the brain by altering the diameter in response to lumen pressure to maintain constant cerebral blood flow. Large conductance potassium (BK) channels are known to regulate the myogenic response. However, it is not clear how aging will influence the myogenic response via altering BK channel function in males and females. Here, using vascular reactivity, patch‐clamp and biochemical methods, we found that age‐associated changes in BK channel subunit expression and function alter myogenic response in a sex‐specific manner. Aging exaggerated the myogenic response of MCA of females but did not change the myogenic response in males. Aging abolished differences in myogenic tone of MCA (MT as determined from active and passive diameters) in males and females. Aging, while decreased wall to lumen ratio in females, it increased in males revealing a sex‐specific difference in MCA remodeling. Aging while decreased total K channel and BK channel currents in vascular smooth muscle cells (VSMCs) isolated from female vessels, it did not affect males. Spontaneous transient outward currents (STOC) that represent BK function are also decreased with aging in both males and females. However, the magnitude of the decrease in STOC amplitude and frequency is much greater in aged females than aged males. While aging increased BKα subunit, it decreased β1 subunit protein in cerebral vessels of both males and females. Age‐associated increase in BKα subunit is similar between males and females. However, there is a greater and significant reduction of BKβ1 subunit protein in aged females than aged males. Activation of BKα and β1 subunits either individually or both failed to decrease MT of MCA isolated from aged males and females at physiological lumen pressures. Besides, aging diminished acute estradiol (17βE)‐mediated decrease in MT either alone or combined with BKβ1 agonist in females. However, this combination significantly decreased MT in ovariectomy females that are chronically supplemented with 17βE via increasing BKβ1 protein content. Overall our results suggest that age‐associated changes in cerebral vascular structure and function and that of BK channel subunit expression and function are sex‐specific. Chronic supplementation of 17βE increases BKβ1 protein content, and its activation by agonist combined with acute 17βE attenuates MT in aged females.Support or Funding InformationSupported by AHA SDG (13SDG14000006) and IRSP from UMMC to Mallikarjuna R. Pabbidi.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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