Functional alterations in cerebrovascular K⁺ and Ca²⁺ 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+ (BKCa), voltage-gated K + (Kv), and L-type voltage-dependent Ca2+ (CaL) currents of Sus and control (Con) rat cerebral VSMCs were investigated with a whole cell voltage-clamp technique. Under the same experimental conditions, Kv, BKCa, and CaL currents of cerebral VSMCs from adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were also investigated. Kv 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 BKCa, and CaL current densities increased [BKCa: 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: Kv 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 BKCa and CaL current densities increased [BKCa: 2.54 ± 0.47 (n = 11) vs. 1.12 ± 0.33 (n = 12) pA/pF at +20 mV (P < 0.05); CaL: -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. Copyright © 2005 the American Physiological Society.