Cheuk B L Y, Ko W H, Wong P Y D
Department of Physiology, The Chinese University of Hong Kong, Shatin, NT.
J Cell Physiol. 2002 May;191(2):217-26. doi: 10.1002/jcp.10086.
Lysylbradykinin (LBK) added to the apical or basolateral side of cultured rat epididymal monolayers stimulated a rise in short-circuit current (Isc) due to anion secretion. The concentration-response relationships for the apical and basolateral applications have EC50 value of 0.001 microM. The responses to apical or basolateral application of LBK were blocked by WIN64338, a specific B2 receptor antagonist, but not by Des-Arg9,[Leu8]-BK, a specific B1 receptor antagonist, indicating that the LBK effects were mediated through B2 bradykinin receptors. Experiments to desensitize the B2 receptors by repeated stimulation have demonstrated that the responses to apical or basolateral LBK were due to discrete receptors on the apical or basolateral surface. In epithelia clamped in the Ussing chambers, addition of LBK to the apical or basolateral surface evoked release of PGE2 into the apical and basolateral bathing solutions over the first 10 min following hormone addition. LBK added to the basolateral side elicited a greater release than it was added to the apical side. Pretreatment of the epithelia with piroxicam (5 microM) abolished PGE2 release elicited by apical or basolateral LBK and abrogated the Isc induced by basolateral LBK. However, the rise in Isc induced by apical LBK was reduced by 31.3% only. The anion secretion response to apical LBK was not affected by MDL-12330A, an adenylate cyclase inhibitor, but greatly attenuated by thapsigargin, an inhibitor of intracellular Ca2+ release. However, the reverse effects were seen for basolateral LBK. It is concluded that distinct pathways are involved in the stimulation of anion secretion by apical or basolateral LBK. The response to basolateral LBK was COX-dependent, mediated by PGE2 and involves cAMP as second messenger. In contrast, the response to apical LBK is largely COX-independent, not mediated by PCE2 and involves Ca2+ as intracellular messenger.
将赖氨酰缓激肽（LBK）添加到培养的大鼠附睾单层细胞的顶端或基底外侧，会因阴离子分泌而刺激短路电流（Isc）升高。顶端和基底外侧应用的浓度-反应关系的半数有效浓度（EC50）值为0.001微摩尔。顶端或基底外侧应用LBK的反应被特异性B2受体拮抗剂WIN64338阻断，但未被特异性B1受体拮抗剂去-精氨酸9，[亮氨酸8]-缓激肽（Des-Arg9，[Leu8]-BK）阻断，这表明LBK的作用是通过B2缓激肽受体介导的。通过重复刺激使B2受体脱敏的实验表明，对顶端或基底外侧LBK的反应是由于顶端或基底外侧表面的离散受体引起的。在置于尤斯灌流小室中的上皮细胞中，在添加激素后的最初10分钟内，将LBK添加到顶端或基底外侧表面会引起前列腺素E2（PGE2）释放到顶端和基底外侧的浴液中。添加到基底外侧的LBK引起的释放比添加到顶端的更多。用吡罗昔康（5微摩尔）预处理上皮细胞可消除顶端或基底外侧LBK引起的PGE2释放，并消除基底外侧LBK诱导的Isc。然而，顶端LBK诱导的Isc升高仅降低了31.3%。顶端LBK的阴离子分泌反应不受腺苷酸环化酶抑制剂MDL-12330A的影响，但被细胞内Ca2+释放抑制剂毒胡萝卜素大大减弱。然而，基底外侧LBK则出现相反的效果。结论是，顶端或基底外侧LBK刺激阴离子分泌涉及不同的途径。对基底外侧LBK的反应是COX依赖性的，由PGE2介导，涉及cAMP作为第二信使。相比之下，对顶端LBK的反应在很大程度上是COX非依赖性的，不由PCE2介导，涉及Ca2+作为细胞内信使。
