TY - JOUR
T1 - Electrophysiologically distinct smooth muscle cell subtypes in rat conduit and resistance pulmonary arteries
AU - Smirnov, S V
AU - Beck, R
AU - Tammaro, P
AU - Ishii, T
AU - Aaronson, P I
PY - 2002/2/1
Y1 - 2002/2/1
N2 - Pulmonary arteries (PAs), particularly those of the rat, demonstrate a prominent voltage-gated K+ (Kv) current (I-Kv), which plays an important role in the regulation of the resting potential. No detailed characterization of electrophysiological and pharmacological properties of I-Kv, particularly in resistance PA myocytes (PAMs), has been performed. The aim of the present study was therefore to compare I-Kv in rat conduit and resistance PAMs using the standard patch clamp technique. We found that 67 % of conduit PAMs demonstrated a large, rapidly activating I-Kv which was potently blocked by 4-aminopyridine (4-AP; IC50, 232 muM), but was almost insensitive to TEA (18 % block at 20 mm). Thirty-three percent of cells exhibited a smaller, more slowly activating I-Kv which was TEA sensitive (IC50, 2.6 mM) but relatively insensitive to 4-AP (37 % block at 20 mm). These currents (termed I-Kv1 and I-Kv2, respectively) inactivated over different ranges of potential (V-0.5 = -20.2 vs. -39.1 mV, respectively). All resistance PAMs demonstrated a large, rapidly activating and TEA-insensitive K+ current resembling I-Kv1 (termed I-KvR), but differing significantly from it with respect to 4-AP sensitivity (IC50, 352 muM), activation rate, and inactivation potential range (V-0.5, -27.4 mV). Thus, cells from conduit PAMs fall into two populations with respect to functional I-Kv expression, while resistance arteries uniformly demonstrate a third type of I-Kv. Comparison of the properties of the native I-Kv with those of cloned Kv channel currents suggest that I-Kv1 and I-KvR are likely to be mediated by Kv1.5-containing homo/heteromultimers, while I-Kv2 involves a Kv2.1 alpha-subunit.
AB - Pulmonary arteries (PAs), particularly those of the rat, demonstrate a prominent voltage-gated K+ (Kv) current (I-Kv), which plays an important role in the regulation of the resting potential. No detailed characterization of electrophysiological and pharmacological properties of I-Kv, particularly in resistance PA myocytes (PAMs), has been performed. The aim of the present study was therefore to compare I-Kv in rat conduit and resistance PAMs using the standard patch clamp technique. We found that 67 % of conduit PAMs demonstrated a large, rapidly activating I-Kv which was potently blocked by 4-aminopyridine (4-AP; IC50, 232 muM), but was almost insensitive to TEA (18 % block at 20 mm). Thirty-three percent of cells exhibited a smaller, more slowly activating I-Kv which was TEA sensitive (IC50, 2.6 mM) but relatively insensitive to 4-AP (37 % block at 20 mm). These currents (termed I-Kv1 and I-Kv2, respectively) inactivated over different ranges of potential (V-0.5 = -20.2 vs. -39.1 mV, respectively). All resistance PAMs demonstrated a large, rapidly activating and TEA-insensitive K+ current resembling I-Kv1 (termed I-KvR), but differing significantly from it with respect to 4-AP sensitivity (IC50, 352 muM), activation rate, and inactivation potential range (V-0.5, -27.4 mV). Thus, cells from conduit PAMs fall into two populations with respect to functional I-Kv expression, while resistance arteries uniformly demonstrate a third type of I-Kv. Comparison of the properties of the native I-Kv with those of cloned Kv channel currents suggest that I-Kv1 and I-KvR are likely to be mediated by Kv1.5-containing homo/heteromultimers, while I-Kv2 involves a Kv2.1 alpha-subunit.
UR - http://www.scopus.com/inward/record.url?scp=0036487067&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2001.013003
DO - 10.1113/jphysiol.2001.013003
M3 - Article
SN - 1469-7793
VL - 538
SP - 867
EP - 878
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 3
ER -