Differential effects of GTP gamma S on acid and pepsinogen secretion by permeable gastric glands.
Differential effects of GTP gamma S on acid and pepsinogen secretion by permeable gastric glands.
复制标题
GTP γ S 对可渗透性胃腺分泌酸和胃蛋白酶原的不同影响。
DOI：
10.1152/ajpgi.1996.270.6.g962
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Hersey,SJ
中科院分区：
文献类型：
--
作者：
Miller,MD;Hersey,SJ
用金黄色葡萄球菌α-毒素透化从兔胃分离的胃腺。壁细胞的酸分泌，作为衡量的弱碱的积累，被抑制与α-毒素孵育，但可以通过添加外源性ATP（1 mM）恢复。渗透性腺体被发现保留酸分泌反应受体连接的促分泌素，组胺和卡巴胆碱，以及细胞内介质，毛喉素和8-溴腺苷3 '，5'-环磷酸，表明存在完整的，功能性的细胞内耦合机制。渗透性腺体的基础和刺激性酸分泌均被Mg 2+螯合剂反式-1，2-二氨基环己烷-N，N，N '，N'-四乙酸（CDTA; 5 mM）阻断，而CDTA对非渗透性腺体没有影响。这些结果被解释为表明α-毒素使壁细胞透化为中等大小的分子，而不引起关键细胞内组分的损失。组胺和卡巴胆碱的酸分泌反应在含有低水平（< 50 nM）游离Ca 2+的培养基中持续存在，该培养基由1，2-双（2-氨基苯氧基）乙烷-N，N，N '，N'-四乙酸（0.5 mM）缓冲，表明这些反应不需要大量Ca 2+的变化。包含GTP的不可水解类似物鸟苷5 '-O-（3-硫代三磷酸）（GTP γ S; 100 μ M），导致自发酸分泌的抑制，阻断对所有测试试剂的反应，并抑制刺激的酸分泌。GTP γ S对非渗透性腺体无影响。观察到GTP、鸟苷二磷酸或鸟苷5 '-O-（2-硫代二磷酸）对渗透性或非渗透性腺体的酸分泌无影响。GTP γ S对胃膜囊泡的H+梯度形成无影响，表明它不直接抑制胃H（+）-K（+）-腺苷三磷酸酶。这些结果被解释为表明，GTP γ S在postreceptor位点相互作用，以抑制或逆转壁细胞中刺激分泌偶联的关键步骤。与对壁细胞的作用相反，发现GTP γ S刺激α-毒素透化的主细胞分泌胃蛋白酶原。GTP γ S对酸和胃蛋白酶原分泌的不同影响表明GTP结合蛋白在这两种分泌过程中具有独特的作用。使用α毒素渗透化的胃腺应该被证明有助于定义涉及酸和胃蛋白酶原分泌的刺激-分泌偶联机制。
Gastric glands isolated from rabbit stomach were permeabilized with Staphylococcus aureus alpha-toxin. Acid secretion by parietal cells, as measured by the accumulation of weak base, was inhibited by incubation with alpha-toxin but could be restored by addition of exogenous ATP (1 mM). The permeable glands were found to retain acid secretory responses to receptor-linked secretagogues, histamine and carbachol, as well as to intracellular mediators, forskolin and 8-bromoadenosine 3',5'-cyclic monophosphate, indicating the presence of intact, functional intracellular coupling mechanisms. Both basal and stimulated acid secretion by the permeable glands were blocked by the Mg2+ chelator, trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA; 5 mM), whereas CDTA had no effect on nonpermeabilized glands. These results are interpreted to show that alpha-toxin permeabilizes parietal cells to moderate sized molecules without causing a loss of critical intracellular components. The acid secretory responses to histamine and carbachol persisted in media containing low ( < 50 nM) levels of free Ca2+ buffered by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (0.5 mM), indicating that changes in bulk Ca2+ are not required for these responses. Inclusion of the nonhydrolyzable analogue of GTP, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 100 microM), resulted in inhibition of spontaneous acid secretion, blocked responses to all agents tested, and inhibited stimulated acid secretion. GTP gamma S had no effect on nonpermeabilized glands. No effects on acid secretion by either permeable or nonpermeable glands were observed with GTP, guanosine diphosphate, or guanosine 5'-O-(2-thiodiphosphate). GTP gamma S had no effect on H+ gradient formation by gastric membrane vesicles, showing that it does not inhibit the gastric H(+)-K(+)-adenosinetriphosphatase directly. These results are interpreted to show that GTP gamma S interacts at a postreceptor site to inhibit or reverse a critical step in stimulus-secretion coupling in parietal cells. In contrast to the effect on parietal cells, GTP gamma S was found to stimulate pepsinogen secretion by alpha-toxin-permeabilized chief cells. The differential effects of GTP gamma S on acid and pepsinogen secretions suggest unique roles for GTP binding proteins in these two secretory processes. The use of alpha-toxin-permeabilized gastric glands should prove useful in defining the stimulus-secretion coupling mechanisms involved in both acid and pepsinogen secretions.