Functional alterations in cerebrovascular K(+) and Ca(2+) channels are comparable between simulated microgravity rat and SHR.
Exposure to microgravity leads to a sustained elevation in transmural pressure across the cerebral vasculature due to removal of hydrostatic pressure gradients. We hypothesized that ion channel remodeling in cerebral vascular smooth muscle cells (VSMCs) similar to that associated with hypertension may occur and play a role in upward autoregulation of cerebral vessels during microgravity. Sprague-Dawley rats were subjected to 4-wk tail suspension (Sus) to simulate the cardiovascular effect of microgravity. Large-conductance Ca(2+)-activated K(+) (BK(Ca)), voltage-gated K(+) (K(V)), and L-type voltage-dependent Ca(2+) (Ca(L)) currents of Sus and control (Con) rat cerebral VSMCs were investigated with a whole cell voltage-clamp technique. Under the same experimental conditions, K(V), BK(Ca), and Ca(L) currents of cerebral VSMCs from adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were also investigated. K(V) current density decreased in Sus rats vs. Con rats [1.07 +/- 0.14 (n = 22) vs. 1.31 +/- 0.28 (n = 16) pA/pF at +20 mV (P < 0.05)] and BK(Ca) and Ca(L) current densities increased [BK(Ca): 1.70 +/- 0.37 (n = 23) vs. 0.88 +/- 0.22 (n = 19) pA/pF at +20 mV (P < 0.05); Ca(L): -2.17 +/- 0.21 (n = 35) vs. -1.31 +/- 0.10 (n = 26) pA/pF at +10 mV (P < 0.05)]. Similar changes were also observed in SHR vs. WKY cerebral VSMCs: K(V) current density decreased [1.03 +/- 0.33 (n = 9) vs. 1.62 +/- 0.64 (n = 9) pA/pF at +20 mV (P < 0.05)] and BK(Ca) and Ca(L) current densities increased [BK(Ca): 2.54 +/- 0.47 (n = 11) vs. 1.12 +/- 0.33 (n = 12) pA/pF at +20 mV (P < 0.05); Ca(L): -3.99 +/- 0.53 (n = 12) vs. -2.28 +/- 0.20 (n = 10) pA/pF at +20 mV (P < 0.05)]. These findings support our hypothesis, and their impact on space cardiovascular research is discussed.
Xie
Man-Jiang
MJ
Department of Aerospace Physiology, Fourth Military Medical University, Xi'an 710032, China.
Zhang
Li-Fan
LF
Ma
Jin
J
Cheng
Hong-Wei
HW
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002536:Cerebral Arteries / Q000166:cytology / Q000502:physiology; D004195:Disease Models, Animal; D006973:Hypertension / Q000503:physiopathology*; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D013623:Tail; D018474:Weightlessness Simulation
D020746:Calcium Channels, L-Type; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D002118:Calcium