Papastamatiou Yannis P
Department of Zoology, Hawaii Institute of Marine Biology, University of Hawaii at Manoa, 46-007 Lilipuna Rd, Kaneohe, HI 96744, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2007 May;147(1):37-42. doi: 10.1016/j.cbpa.2006.11.012. Epub 2006 Nov 28.
Vertebrates are known to differ in their response of gastric acid secretion during periods of fasting, yet the reasons for these differences remain unclear. Previously, continuous measurements of gastric pH in leopard sharks (Triakis semifasciata) had determined that acid secretion in this species is continuous. In order to determine if maintaining an empty acidic stomach may reduce digestion time of a subsequent meal, a simple descriptive model based on acid secretion rates was developed. In vivo gastric acid secretion rates were measured using an auto-titration technique. Acid secretion rates were pH dependent, with rates of 6.1+/-3.0 (+/-1 SD) mmol/h when gastric pH was >2.5, and 1.7+/-0.8 mmol/h when pH was 2.0-2.5. Analysis by Western blots suggests that pepsin secretion occurs within 1 h of feeding, and that there is a de-coupling of acid and pepsin secretion. The model estimates that digestion time can be reduced by 5.7+/-1.3 h and pepsin activity increased by 10-100% during that time if the stomach is acidic before feeding. Gastric acid secretion during fasting is hypothesized to reduce digestion time of a subsequent meal in frequently feeding sharks, which may be advantageous for exploiting resources that are spatially and temporally unpredictable.
已知脊椎动物在禁食期间胃酸分泌的反应存在差异，然而这些差异的原因仍不清楚。此前，对豹纹鲨（Triakis semifasciata）胃内pH值的连续测量确定，该物种的胃酸分泌是持续的。为了确定保持空腹酸性胃是否可以减少后续一餐的消化时间，基于胃酸分泌速率建立了一个简单的描述模型。使用自动滴定技术测量体内胃酸分泌速率。胃酸分泌速率与pH值有关，当胃内pH值>2.5时，速率为6.1±3.0（±1标准差）mmol/h，当pH值为2.0 - 2.5时，速率为1.7±0.8 mmol/h。蛋白质印迹分析表明，胃蛋白酶分泌在进食后1小时内发生，并且胃酸和胃蛋白酶分泌存在解偶联。该模型估计，如果进食前胃呈酸性，消化时间可减少5.7±1.3小时，在此期间胃蛋白酶活性可提高10 - 100%。据推测，禁食期间的胃酸分泌可减少频繁进食的鲨鱼后续一餐的消化时间，这可能有利于利用在空间和时间上不可预测的资源。
