Hormonal Regulation of Water and Electrolyte Transport in the Colon

精氨酸加压素(AVP)在体液电解质平衡中起着重要作用，但其对肠道转运的影响尚不完全清楚。我们用Ussing小室和Fura-2检测了AVP对豚鼠远端结肠上皮细胞内钙离子浓度([Ca^&lt；2&gt；]_i)的影响。血清中加入0.1 nM~(-1)mM-AVP可引起短路电流(ISC)和组织电导(GT)浓度依赖性变化。它们包括布美他尼(0.1 mM，浆膜)敏感的ISC增加，显示电源性氯分泌，以及布美他尼(0.1 mM，浆膜)敏感的ISC减少，这意味着电源性K^的分泌。ISC的这两个变化都与GT的增加有关。另一方面，AVP引起对阿米洛利(0.1 mM，粘膜)敏感的ISC和GT的降低，这与抑制电生理钠的吸收是一致的。AVP还以浓度依赖的方式引起隐窝细胞[Ca^&lt；2&gt；]i双相升高。血管加压素V_1受体拮抗剂可阻断血管加压素V_1受体拮抗剂的作用。这些研究表明，AVP通过V_1受体动员豚鼠远端结肠[Ca~(2+)]_i，刺激布美他尼敏感的K~+和Cl~-的分泌，抑制阿米洛利敏感的Na~+吸收。

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.