Centro de Investigaciones Biológicas del Noroeste, S.C., Programa de Planeación Ambiental y Conservación, Instituto Politécnico Nacional 195, Playa Palo de Santa Rita Sur, La Paz, Baja California Sur, C.P. 23096, Mexico.
Sonoma State University, Department of Biology, 1801 E. Cotati Ave., Rohnert Park, CA 94928, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2014 May;171:31-5. doi: 10.1016/j.cbpa.2014.02.007. Epub 2014 Feb 13.
Purine nucleoside phosphorylase (PNP) and xanthine oxidase (XO) are key enzymes involved in the purine salvage pathway. PNP metabolizes purine bases to synthetize purine nucleotides whereas XO catalyzes the oxidation of purines to uric acid. In humans, PNP activity is reported to be high in erythrocytes and XO activity to be low in plasma; however, XO activity increases after ischemic events. XO activity in plasma of northern elephant seals has been reported during prolonged fasting and rest and voluntary associated apneas. The objective of this study was to analyze circulating PNP and XO activities in marine mammals adapted to tolerate repeated cycles of ischemia/reperfusion associated with diving (bottlenose dolphin, northern elephant seal) in comparison with semiaquatic (river otter) and terrestrial mammals (human, pig). PNP activities in plasma and erythrocytes, as well as XO activity in plasma, from all species were quantified by spectrophotometry. No clear relationship in circulating PNP or XO activity could be established between marine, semiaquatic and terrestrial mammals. Erythrocytes from bottlenose dolphins and humans are highly permeable to nucleosides and glucose, intraerythrocyte PNP activity may be related to a release of purine nucleotides from the liver. High-energy costs will probably mean a higher ATP degradation rate in river otters, as compared to northern elephant seals or dolphins. Lower erythrocyte PNP activity and elevated plasma XO activity in northern elephant seal could be associated with fasting and/or sleep- and dive-associated apneas.
嘌呤核苷磷酸化酶 (PNP) 和黄嘌呤氧化酶 (XO) 是参与嘌呤补救途径的关键酶。PNP 将嘌呤碱基代谢为合成嘌呤核苷酸，而 XO 催化嘌呤氧化为尿酸。在人类中，PNP 活性在红细胞中较高，而 XO 活性在血浆中较低；然而，缺血事件后 XO 活性增加。据报道，在长时间禁食、休息和自愿相关的呼吸暂停期间，北方象海豹的血浆中存在 XO 活性。本研究的目的是分析适应耐受与潜水相关的反复缺血/再灌注循环的海洋哺乳动物（宽吻海豚、北方象海豹）与半水生（水獭）和陆生哺乳动物（人类、猪）的循环 PNP 和 XO 活性。通过分光光度法定量测定所有物种的血浆和红细胞中的 PNP 活性以及血浆中的 XO 活性。在海洋、半水生和陆生哺乳动物之间，循环 PNP 或 XO 活性之间没有明显的关系。宽吻海豚和人类的红细胞对核苷和葡萄糖具有很高的通透性，红细胞内 PNP 活性可能与肝脏释放嘌呤核苷酸有关。与北方象海豹或海豚相比，水獭的高能消耗可能意味着更高的 ATP 降解率。北方象海豹的红细胞 PNP 活性较低和血浆 XO 活性升高可能与禁食和/或睡眠和潜水相关的呼吸暂停有关。
