1994 Fiscal Year Final Research Report Summary
Analysis of signal transduction in the macula densa cell.
| Project/Area Number |
05670053
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
General physiology
|
|---|
| Research Institution | KYUSHU UNIVERSITY |
|---|
Principal Investigator |
YOSHITOMI Koji KYUSYU UNIVERSITY,FUCULTY OF MEDICINE,RESEARCH ASSOCIATE, 医学部, 助手 (60137354)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KUROKAWA Kiyoshi TOKYO UNIVERSITY,FUCULTY OF MEDICINE,PROFESSOR., 医学部, 教授 (30167390)
|
|---|
| Project Period (FY) |
1993 – 1994
|
| Keywords | Na transport / kidney / AVP / Cl^- channel / vasopressin / cortical collecting duct / receptor / cyclic AMP |
|---|
| Research Abstract |
To clarify the mechanism of action of AVP on ionic conductances, electrophysiological technique was applied to the rabbit cortical collecting duct (CCD) perfused in vitro. When AVP (100pM) was added to the bath, , transepithelial voltage (V_<gamma>), transepithelial resistace (R_<gamma>) and fractional resistance of the apical membrane fR_A) of the principal cell displayd biphasic responses : Initial increase in lumen negative V_<gamma> (phase I) was associated with decreases in R_<gamma> and fR_A, representing the stimulation of Na^+ conductance. Whereas secondary decrease in V_<gamma> (phase II) was associated with increases in R_<gamma> and fR_A, representing mixed responses of both hyperpolarization of the luminal membrane due to late inhibition of Na^+ conductance and depolarization of the basolateral membrane due to stimulation of Cl^- conductance. Addition of AVP (100pM - 1nM) in the lumen resulted in increases in lumen negative V_<gamma> and R_<gamma>. In principal cells, luminal AVP caused sustained increase in total membrane resistance (Ri), together with a hyperpolarization of the basolateral membrane, representing the inhibition of basolateral Cl^- conductance. Under the condition where Cl^- conductance of the basolateral membrane was stimulated by administration of cAMP in the bath, voltage deflections of the basolateral membrane upon changing Cl^- concentration in the bath from 120 to 12 mM decreased by 88% in the presence of luminal AVP.These observations are in accord with the view that the basolateral Cl^- conductance was inhibited by luminal AVP in the later phase. These data indicate that AVP in the lumen inhibits basolateral Cl^- conductance, which is stimulated by AVP in the bath.
|
