Swelling-Induced K⁺ Fluxes in Vascular Smooth Muscle Cells are Mediated by Charybdotoxin-Sensitive K⁺ Channels

Abstract

This study examines the relative contributions of K-Cl cotransport and K⁺ channels to swelling-induced K⁺ fluxes in vascular smooth muscle cells (VSMC). DIOA known as a potent inhibitor of erythrocyte K-Cl cotransport exerts diverse side-effects on VSMC and can not be used to analyze the role of this carrier in swelling-induced K⁺ fluxes. Other inhibitors of K-Cl cotransport (furosemide, okadaic acid and calyculin A) did not affect K⁺ fluxes in VSMC triggered by swelling. Swelling-induced K⁺ fluxes in VSMC were also not affected by K⁺ channel blockers such as TEA, glibenclamide and apamin, but were blocked by Ba²⁺ and charybdotoxin (ChTX), a potent inhibitor of Ca²⁺- and voltage-gated K⁺ channels. Swelling-induced K⁺ influx in VSMC was diminished in Ca²⁺-free medium and in cells loaded with Ca²⁺ chelator BAPTA, but was not accompanied by detectable elevation of [Ca²⁺]_i. In contrast to Ca²⁺-induced hyperpolarization of erythrocytes triggered by activation of intermediate conductance Ca²⁺-gated K⁺ channels (IK_Ca), neither clotrimazole nor calmodulin antagonists (R24571, trifluoroperazine, fluphenazine) affected swelling-induced K⁺ influx in VSMC. In conclusion, K⁺ fluxes triggered in swollen VSMC are mediated by Ba²⁺- and ChTX-sensitive K⁺ channels. These channels are distinct from IK_Ca expressed in erythrocytes. Their molecular origin and systems involved in the swelling-induced Ca²⁺_i-independent signal transduction pathway need further investigation.

Transient Activation and Delayed Inhibition of Na+,K+,Cl–Cotransport in ATP-treated C11-MDCK Cells Involve Distinct P2Y Receptor Subtypes and Signaling Mechanisms

“…10, trifluoroperazine and W-7 dose-dependently attenuated the increment of NKCC activity triggered by 5-min exposure to ATP with IC 50 values of ϳ2 and 50 M, respectively. Higher efficacy of trifluoroperazine in suppression of transient NKCC activation by ATP is consistent with data on the inhibition by trifluoroperazine and W-7 of Ca 2ϩ -induced conformational transition of CaM obtained in cell-free systems (36).…”

“…To examine the role of basolateral versus apical location of P2Y receptors in NKCC regulation, we employed monolayers of C11 cells seeded on 1-cm 2 permeable inserts (Corning brand transwell plate inserts; Fisher) as described previously (25 36 Cl distribution between C11 cells and extracellular medium under steady-state conditions, as described previously (4), and calculated as V ϭ A/am, where A is the radioactivity of the cell lysate (cpm), m is the protein content (mg), and a is the specific radioactivity of the incubation medium (cpm/nmol).…”

Cell-volume-dependent vascular smooth muscle contraction: role of Na+, K+, 2Cl? cotransport, intracellular Cl? and L-type Ca2+ channels

“…2a, curve 3). These results suggest that suppression of bumetanide-resistant K + influx in hyperosmotic medium is caused by the inhibition of KCC reciprocally regulated by cell volume and detected in our previous studies [6,43].…”

Hemolysis of Erythrocytes by Granulysin-Derived Peptides but Not by Granulysin

“…Both Kir and K ATP channels are inhibited by Ba 2ϩ , with ID 50 s of 0.002 and 0.1 mM, respectively (30), and BaCl 2 inhibited crude-venom-induced hemolysis (28). Kv, K Ca , and K ATP are also extremely sensitive to externally applied TEA (30), and apamin selectively blocks SK Ca (4). Taken together, the data suggest that a variety of K ϩ channels on erythrocyte membranes are involved in G8-induced hemolysis.…”