Abstract
The resting membrane potential (RP) of vascular smooth muscle cells (VSMCs) is a major determinant of cytosolic calcium concentration and vascular tone. The heterogeneity of RPs and its underlying mechanism among different vascular beds remain poorly understood. We compared the RPs and vasomotion properties between the guinea pig spiral modiolar artery (SMA), brain arterioles (BA) and mesenteric arteries (MA). We found: 1) RPs showed a robust bimodal distribution peaked at -76 and -40 mV evenly in the SMA, unevenly at -77 and -51 mV in the BA and ~-71 and -52 mV in the MA. Ba2+ 0.1 mM eliminated their high RP peaks ~-75 mV. 2) Cells with low RP (~-45 mV) hyperpolarized in response to 10 mM extracellular K+, while cells with a high RP depolarized, and cells with intermediate RP (~-58 mV) displayed an initial hyperpolarization followed by prolonged depolarization. Moderate high K+ typically induced dilation, constriction and a dilation followed by constriction in the SMA, MA and BA, respectively. 3) Boltzmann-fit analysis of the Ba2+-sensitive inward rectifier K+ (Kir) whole-cell current showed that the maximum Kir conductance density significantly differed among the vessels, and the half-activation voltage was significantly more negative in the MA. 4) Corresponding to the whole-cell data, computational modeling simulated the three RP distribution patterns and the dynamics of RP changes obtained experimentally, including the regenerative swift shifts between the two RP levels after reaching a threshold. 5) Molecular works revealed strong Kir2.1 and Kir2.2 transcripts and Kir2.1 immunolabeling in all 3 vessels, while Kir2.3 and Kir2.4 transcript levels varied. We conclude that a dense expression of functional Kir2.X channels underlies the more negative RPs in endothelial cells and a subset of VSMC in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles. The fast Kir-based regenerative shifts between two RP states could form a critical mechanism for conduction/spread of vasomotion along the arteriole axis.
Highlights
Auditory transduction is associated with heavy energy consumption [1], and is extremely vulnerable to vascular disturbances
We conclude that a dense expression of functional Kir2.X channels underlies the more negative resting potentials (RP) in endothelial cells and a subset of vascular smooth muscle cells (VSMCs) in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles
We report here that arterioles from the mesentery and brain pia have a very different RP distribution from that of the spiral modiolar artery (SMA) (Fig 1A)
Summary
Auditory transduction is associated with heavy energy consumption [1], and is extremely vulnerable to vascular disturbances. Accumulated evidences suggest that vascular malfunction contributes to age-related hearing loss [6,7,8], Meniere’s disease [9], some forms of sudden deafness [10] and increased risk of drug- and noise-induced ototoxicity [11]. To effectively treat those hearing disorders, a better understanding of how CBF is regulated is critical. The cochlear spiral modiolar artery (SMA) is of particular interest because it is the primary blood supplier to the cochlea [12]. We demonstrated that the resting potentials (RP) of these cells show a robust bimodal distribution, peaking at ~-40 and -75 mV, called low and high RP, respectively [16] (see Fig 1A)
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