Enhancement of receptor-operated cation current and TRPC6 expression in arterial smooth muscle cells of deoxycorticosterone acetate-salt hypertensive rats.
OBJECTIVE
In deoxycorticosterone acetate (DOCA)-salt hypertensive rats, altered reactivity of blood vessels to vasoactive agonists is frequently associated with an elevation in blood pressure. Canonical transient receptor potential (TRPC) channels are believed to encode receptor-operated cation channels (ROC), the activation of which is involved in smooth muscle depolarization and vasoconstriction. The aims of the present study were to investigate whether the ROC current is increased in DOCA-hypertensive rats and determine whether aldosterone directly enhances the expression of TRPC.


METHODS
The nystatin-perforated patch-clamp technique was used for the recording of receptor-stimulated ion currents in mesenteric arterial smooth muscle cells, which were enzymatically dispersed from sham-operated and DOCA-salt hypertensive rats. Expressions of TRPCs were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) and by Western blot analysis.


RESULTS
Receptor-stimulated currents activated by 5-hydroxytryptamine (serotonin) and norepinephrine were increased significantly in the mesenteric arterial smooth muscle cells of DOCA-salt hypertensive rats compared to sham-operated rats. Ion-substitution experiments revealed that the enhanced currents were cation currents (ROC currents). Enhanced expression of TRPC6 in mesenteric arteries from DOCA-salt hypertensive rats was demonstrated by real-time RT-PCR. Up-regulation of TRPC6 by aldosterone treatment in vitro was also observed in A7r5 cells by RT-PCR and in western blots.


CONCLUSIONS
These results suggest that aldosterone enhances TRPC6 expression and ROC currents in vascular smooth muscle cells, and that this may in turn contribute to altered vascular reactivity and to hypertension.
Bae
Young Min
YM
Artificial Muscle Research Center, Departments of Physiology, College of Medicine, Konkuk University, Choongju, Korea.
Kim
Aeran
A
Lee
Young Joo
YJ
Lim
Wonchung
W
Noh
Yun-Hee
YH
Kim
Eun-Ju
EJ
Kim
Junghwan
J
Kim
Tae-Kyung
TK
Park
Sang Woong
SW
Kim
Bokyung
B
Cho
Sung Il
SI
Kim
Duk-Kyung
DK
Ho
Won-Kyung
WK
D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology; D001158:Arteries / Q000166:cytology*; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D015220:Calcium Channels / Q000096:biosynthesis* / Q000187:drug effects*; D003900:Desoxycorticosterone; D004195:Disease Models, Animal; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D017538:Mesenteric Artery, Superior / Q000166:cytology; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012701:Serotonin / Q000494:pharmacology; D018490:Serotonin Agents / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000096:biosynthesis* / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D015220:Calcium Channels; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D018490:Serotonin Agents; D050052:TRPC Cation Channels; C492145:Trpc6 protein, rat; D014662:Vasoconstrictor Agents; D012701:Serotonin; D003900:Desoxycorticosterone; D000450:Aldosterone; D009638:Norepinephrine