Changes of the potassium currents in rat aortic smooth muscle cells during postnatal development.
This study was designed to investigate the role and regulation of arterial K+ channels during postnatal development. Rat thoracic aortic segments were suspended for isometric tension and resting membrane potential (RMP) recording. Contraction in response to 4-aminopyridine (4-AP) was similar in 4-, 8- and 12-week-old rats but was higher in 1-day-old rats. Contraction in response to tetraethylammonium (TEA) increased after 4 weeks. TEA increased the contractions evoked by noradrenaline in the aorta from 8- and 12-week-old rats but not from 1-day- and 4-week-old rats. RMP did not change during development. Patch-clamp studies of freshly isolated smooth muscle cells from the same aortas bathed in Ca2+-free medium showed a voltage-dependent K+ current (IK) sensitive to 4-AP. This current remained stable at all ages whereas the density of the total IK, recorded in the presence of Ca2+, showed a twofold increase between 4 and 8 weeks. This current was highly sensitive to TEA and charybdotoxin. The binding site density of 125I-labelled charybdotoxin was threefold higher in the membranes of aortas from 12-week-old compared to 4-week-old rats. These results indicate that changes in K+ channel distribution occur in the rat aorta during postnatal development. These are related to an increase in the expression of charybdotoxin-sensitive Ca2+-activated K+ channels.
Gomez
J P
JP
Laboratoire de Pharmacologie, Université Catholique de Louvain, Bruxelles, Belgium.
Ghisdal
P
P
Morel
N
N
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D015761:4-Aminopyridine / Q000494:pharmacology; D000375:Aging; D000818:Animals; D001013:Aorta, Thoracic / Q000254:growth & development; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D018999:Charybdotoxin / Q000494:pharmacology; D004553:Electric Conductivity; D008297:Male; D008564:Membrane Potentials; D009119:Muscle Contraction / Q000187:drug effects; D024510:Muscle Development; D009131:Muscle, Smooth, Vascular / Q000254:growth & development* / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects
D002120:Calcium Channel Agonists; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D018999:Charybdotoxin; D019789:Tetraethylammonium; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D015761:4-Aminopyridine; D002118:Calcium; D009638:Norepinephrine