Esbaugh A J, Secor S M, Grosell M
Department of Marine Science, University of Texas at Austin, Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78418, USA.
Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35405, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2015 Oct;188:120-6. doi: 10.1016/j.cbpa.2015.06.029. Epub 2015 Jun 27.
Burmese pythons are sit-and-wait predators that are well adapted to go long periods without food, yet subsequently consume and digest single meals that can exceed their body weight. These large feeding events result in a dramatic alkaline tide that is compensated by a hypoventilatory response that normalizes plasma pH; however, little is known regarding how plasma HCO3(-) is lowered in the days post-feeding. The current study demonstrated that Burmese pythons contain the cellular machinery for renal acid-base compensation and actively remodel the kidney to limit HCO3(-) reabsorption in the post-feeding period. After being fed a 25% body weight meal plasma total CO2 was elevated by 1.5-fold after 1 day, but returned to control concentrations by 4 days post-feeding (d pf). Gene expression analysis was used to verify the presence of carbonic anhydrase (CA) II, IV and XIII, Na(+) H(+) exchanger 3 (NHE3), the Na(+) HCO3(-) co-transporter (NBC) and V-type ATPase. CA IV expression was significantly down-regulated at 3 dpf versus fasted controls. This was supported by activity analysis that showed a significant decrease in the amount of GPI-linked CA activity in isolated kidney membranes at 3 dpf versus fasted controls. In addition, V-type ATPase activity was significantly up-regulated at 3 dpf; no change in gene expression was observed. Both CA II and NHE3 expression was up-regulated at 3 dpf, which may be related to post-prandial ion balance. These results suggest that Burmese pythons actively remodel their kidney after feeding, which would in part benefit renal HCO3(-) clearance.
缅甸蟒是坐等型捕食者，非常适应长时间不进食，但随后能吞食并消化超过自身重量的单餐食物。这些大量进食事件会导致显著的碱潮，通过低通气反应来补偿，使血浆pH值恢复正常；然而，关于进食后数天血浆HCO3(-)如何降低，人们知之甚少。当前研究表明，缅甸蟒具备肾脏酸碱补偿的细胞机制，并在进食后积极重塑肾脏，以限制HCO3(-)的重吸收。喂食相当于体重25%的食物后，血浆总二氧化碳在1天后升高了1.5倍，但在进食后4天（d pf）恢复到对照浓度。基因表达分析用于验证碳酸酐酶（CA）II、IV和XIII、钠氢交换体3（NHE3）、钠碳酸氢根共转运体（NBC）和V型ATP酶的存在。与禁食对照相比，CA IV表达在3 dpf时显著下调。活性分析也支持了这一点，该分析表明，与禁食对照相比，3 dpf时分离的肾膜中GPI连接的CA活性量显著降低。此外，V型ATP酶活性在3 dpf时显著上调；未观察到基因表达的变化。CA II和NHE3表达在3 dpf时均上调，这可能与餐后离子平衡有关。这些结果表明，缅甸蟒在进食后会积极重塑其肾脏，这在一定程度上有利于肾脏清除HCO3(-)。
