Ghrelin signalling in guinea-pig femoral artery smooth muscle cells.
OBJECTIVE
Our aim was to study the new signalling pathway of ghrelin in the guinea-pig femoral artery using the outward I(K) as a sensor.


METHODS
Whole-cell patch-clamp experiments were performed on single smooth muscle cells, freshly isolated from the guinea-pig femoral artery. The contractile force of isometric preparations of the same artery was measured using a wire-myograph.


RESULTS
In a Ca2+- and nicardipine-containing external solution, 1 mmol L(-1) tetraethylammonium reduced the net I(K) by 49 +/- 7%. This effect was similar and not additive to the effect of the specific BK(Ca) channel inhibitor iberiotoxin. Ghrelin (10(-7) mol L(-1)) quickly and significantly reduced the amplitudes of tetraethylammonium- and iberiotoxin-sensitive currents through BK(Ca) channels. The application of 5 x 10(-6) mol L(-1) desacyl ghrelin did not affect the amplitude of the control I(K) but it successfully prevented the ghrelin-induced I(K) decrease. The effect of ghrelin on I(K) was insensitive to selective inhibitors of cAMP-dependent protein kinase, soluble guanylyl cyclase, cGMP-dependent protein kinase or a calmodulin antagonist, but was effectively antagonized by blockers of BK(Ca) channels, phosphatidylinositol-phospholipase C, phosphatidylcholine-phospholipase C, protein kinase C, SERCA, IP(3)-induced Ca2+ release and by pertussis toxin. The ghrelin-induced increase in the force of contractions was blocked when iberiotoxin (10(-7) mol L(-1)) was present in the bath solution.


CONCLUSIONS
Ghrelin reduces I(K(Ca)) in femoral artery myocytes by a mechanism that requires activation of Galpha(i/o)-proteins, phosphatidylinositol phospholipase C, phosphatidylcholine phospholipase C, protein kinase C and IP(3)-induced Ca2+ release.
Mladenov
M I
MI
Department of Ion Channels, Institute of Biophysics, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Hristov
K L
KL
Dimitrova
D Z
DZ
Dimitriova
D Z
DZ
Schubert
R
R
Lubomirov
L T
LT
Gjorgoski
I K
IK
Duridanova
D B
DB
Gagov
H S
HS
D000818:Animals; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D005263:Femoral Artery / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D054439:Ghrelin / Q000494:pharmacology*; D006168:Guinea Pigs; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D054801:Phosphoinositide Phospholipase C / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D010738:Type C Phospholipases / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D019332:Endothelin-1; D054439:Ghrelin; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; C064719:iberiotoxin; D011493:Protein Kinase C; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C105598:phosphatidylcholine-specific phospholipase C