Hoch B S, Gorfien P C, Linzer D, Fusco M J, Levine S D
Department of Medicine, Maimonides Medical Center, Brooklyn 11219.
Am J Physiol. 1989 May;256(5 Pt 2):F948-53. doi: 10.1152/ajprenal.1989.256.5.F948.
Mercurial reagents inhibit the water permeability of erythrocytes and proximal renal tubule. We examined the effect of two such agents on vasopressin-induced water transport across toad urinary bladder. Water flows were measured in unfixed tissues and in tissues fixed either with N-ethylmaleimide (NEM) or with glutaraldehyde. When added concurrently with 20 mU/ml vasopressin, 1 mM mucosal p-chloromercuribenzene-sulfonic acid (p-CMBS) inhibited water flow within 1 h. p-CMBS also inhibited flow in tissues that had been fixed with mucosal NEM after stimulation with vasopressin. However, p-CMBS did not affect flow in glutaraldehyde-fixed tissues. In contrast, HgCl2 inhibited water flow and urea permeability even in tissues that had been fixed with glutaraldehyde after stimulation with vasopressin. Inhibition was more pronounced when HgCl2 was added to the mucosal rather than the serosal bathing medium and was not reversed by dithiothreitol. HgCl2 did not diminish the frequency or area of luminal membrane aggregates observed by freeze-fracture electron microscopy. HgCl2 also did not affect amphotericin-induced water permeability in glutaraldehyde-treated tissues, suggesting that it did not diminish the permeability of cellular barriers to flow. Our results parallel closely those reported by other investigators for water flow across erythrocytes and proximal renal tubule and suggest that mercurial reagents can directly block the vasopressin-induced water channel. The water channel at the apical membrane of the toad bladder may prove to share structural similarity with that constantly present in erythrocytes and proximal renal tubule.
汞试剂可抑制红细胞和近端肾小管的水通透性。我们研究了两种此类试剂对血管升压素诱导的蟾蜍膀胱水转运的影响。在未固定的组织以及用N - 乙基马来酰亚胺（NEM）或戊二醛固定的组织中测量水流量。当与20 mU/ml血管升压素同时添加时，1 mM黏膜对氯汞苯磺酸（p - CMBS）在1小时内抑制水流量。p - CMBS也抑制血管升压素刺激后用黏膜NEM固定的组织中的水流量。然而，p - CMBS对戊二醛固定的组织中的水流量没有影响。相比之下，HgCl₂即使在血管升压素刺激后用戊二醛固定的组织中也能抑制水流量和尿素通透性。当HgCl₂添加到黏膜而非浆膜浴液中时抑制作用更明显，并且二硫苏糖醇不能使其逆转。HgCl₂没有减少冷冻断裂电子显微镜观察到的腔面膜聚集体的频率或面积。HgCl₂也不影响戊二醛处理的组织中两性霉素诱导的水通透性，这表明它没有降低细胞屏障对水流的通透性。我们的结果与其他研究者报道的关于红细胞和近端肾小管水流量的结果非常相似，表明汞试剂可直接阻断血管升压素诱导的水通道。蟾蜍膀胱顶端膜的水通道可能与红细胞和近端肾小管中始终存在的水通道在结构上具有相似性。
