首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Bethanechol inhibition of chicken intestinal brush border Na/H exchange: role of protein kinase C and other calcium-dependent processes.
Authors:M W Musch  D Drabik-Arvans  M C Rao  E B Chang
Institution:Department of Medicine, University of Chicago, Illinois 60637.
Abstract:Bethanechol, a muscarinic agonist, inhibits the initial rate of amiloride-sensitive Na uptake by intact mucosa of avian small intestine as well as by isolated chicken villus enterocytes, an effect that is maximal at 90 seconds and reverses by 6 minutes. Bethanechol similarly decreases intracellular pH in isolated cells suspended in bicarbonate-free buffer in a time course similar to inhibition of enterocyte Na uptake, suggesting inhibition of Na/H exchange. In brush border membrane vesicles rapidly prepared from cells stimulated with bethanechol, proton-dependent 22Na uptake is transiently inhibited in a time course similar to inhibition of cell Na uptake. Bethanechol also stimulates transient translocation of protein kinase C from the cytosol to the particulate fraction, a portion of this activity translocating to the brush border membrane. To determine the calcium dependence of bethanechol's action, enterocytes were loaded with varying concentrations of the calcium buffering agent quin-2. Inhibition of cell Na uptake by the calcium ionophore ionomycin could be completely reversed by quin-2 buffering in a concentration-dependent manner. In contrast, quin-2 buffering had little or no effect on the inhibition of Na uptake caused by the protein kinase C activators phorbol esters and oleoylacetylglycerol. Bethanechol's inhibitory effects were partially, but not completely reversed by quin-2 buffering. These data suggest that the effects of bethanechol on chicken villus enterocyte brush border Na/H exchange are mediated by calcium-dependent process(es) as well as by protein kinase C.
Keywords:
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号