1995 Fiscal Year Final Research Report Summary
Hormonal Regulation of Water and Electrolyte Transport in the Colon
| Project/Area Number |
06670536
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Gastroenterology
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| Research Institution | Hamamatsu University School of Medicine |
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Principal Investigator |
HANAI Hiroyuki Hamamatsu University School of Medicine. First Dept. of Medicine. Assistant Professor., 医学部附属病院, 講師 (80208553)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Eizo Hamamatsu University School of Medicine. First Dept. of Medicine. Professor., 医学部, 教授 (10010414)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Vasopressin / Colon / V1 receptor / Cytosolic calcium / Sodium absorption / Potassium secretion / Chloride secretion |
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| Research Abstract |
Arginine vasopressin (AVP) plays an important role in fluid and electrolyte homeostasis, but its effect on intestinal transport is not fully elucidated. We examined the effect of AVP on colonic mucosal transport using Ussing chambers and cytosolic calcium concentration ([Ca^<2+>]_i) using fura-2 in guinea pig distal colonic epithelium. Serosally added 0.1 nM-1 mM-AVP caused concentration dependent changes in short circuit current (Isc) and tissue conductance (Gt). They include a bumetanide (0.1 mM,serosal)-sensitive increase in Isc which shows electrogenic Cl secretion, and a bumetanide (0.1 mM,serosal)-sensitive decrease in Isc which means electrogenic K^+ secretion. Both changes in Isc were associated with increases in Gt. On the other hand, AVP caused an amiloride (0.1 mM,mucosal)-sensitive decrease in Isc and Gt which coincided inhibition of electrogenic Na^+ absorption. AVP also caused biphasic increases in [Ca^<2+>]_i of crypt cells in a concentration dependent manner. [Ca^<2+>]_i in surface epithelial cells also responded to AVP.All these responses to AVP were abolished by a vasopressin V_1-antagonist. These studies indicate that AVP mobilizes [Ca^<2+>]_i via V_1-receptor, stimulates both bumetanide-sensitive K^+ and Cl^- secretion, and inhibits an amiloride-sensitive Na^+ absorption in guinea pig distal colon.
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