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首页> 外文期刊>The Journal of Experimental Biology >Cardiac responses to hypercapnia in larval zebrafish (Danio rerio): the links between CO2 chemoreception, catecholamines and carbonic anhydrase
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Cardiac responses to hypercapnia in larval zebrafish (Danio rerio): the links between CO2 chemoreception, catecholamines and carbonic anhydrase

机译：幼虫斑马鱼对高碳酸血症的心脏反应：二氧化碳化学感受，儿茶酚胺和碳酸酐酶之间的联系

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The ontogeny of carbon dioxide (CO2) sensing in zebrafish (Danio rerio) has not been examined. In this study, CO2-mediated increases in heart rate were used to gauge the capacity of zebrafish larvae to sense CO2. CO2 is thought to be detected via neuroepithelial cells (NECs), which are homologous to mammalian carotid body glomus cells. Larvae at 5 days post-fertilization (d.p.f.) exhibited tachycardia when exposed for 30 min to 0.75% CO2 (similar to 5.63 mmHg); at 7 d.p.f., tachycardia was elicited by 0.5% CO2 (similar to 3.75 mmHg). Based on pharmacological evidence using beta-adrenergic receptor (beta-AR) antagonists, and confirmed by beta(1)-AR translational gene knockdown using morpholinos, the reflex tachycardia accompanying hypercapnia was probably mediated by the interaction of catecholamines with cardiac beta(1) receptors. Because the cardiac response to hypercapnia was abolished by the ganglionic blocker hexamethonium, it is probable that the reflex cardio-acceleration was mediated by catecholamines derived from sympathetic adrenergic neurons. Owing to its likely role in facilitating intracellular acidification during exposure to hypercapnia, it was hypothesized that carbonic anhydrase (CA) is involved in CO2 sensing, and that inhibition of CA activity would blunt the downstream responses. Indeed, the cardiac response to hypercapnia (0.75% CO2) was reduced in fish at 5 d.p.f. exposed to acetazolamide, a CA inhibitor, and in fish experiencing zCAc (CA2-like a) knockdown. Successful knockdown of zCAc was confirmed by CA activity measurements, western blotting and immunocytochemistry. Co-injection of embryos with zCAc morpholino and mRNA modified at the morpholino binding site restored normal levels of CA activity and protein levels, and restored (rescued) the usual cardiac responses to hypercapnia. These data, combined with the finding that zCAc is expressed in NECs located on the skin, suggest that the afferent limb of the CO2-induced cardiac reflex in zebrafish larvae is initiated by coetaneous CO2-sensing neuroepithelial cells
机译：斑马鱼（Danio rerio）中的二氧化碳（CO2）传感的本体论尚未进行检查。在这项研究中，CO2介导的心率增加被用于评估斑马鱼幼虫感知CO2的能力。二氧化碳被认为是通过神经上皮细胞（NECs）检测到的，而神经上皮细胞与哺乳动物的颈动脉glomus细胞同源。受精后5天（d.p.f.）的幼虫暴露于0.75％CO2（约5.63 mmHg）30分钟后表现出心动过速;在d.p.f. 7 d时，心动过速是由0.5％的CO2（约3.75 mmHg）引起的。根据使用β-肾上腺素受体（β-AR）拮抗剂的药理学证据，并通过使用吗啉代糖的β（1）-AR翻译基因敲低证实，伴随高碳酸血症的反射性心动过速可能是由儿茶酚胺与心脏β（1）相互作用介导的受体。由于神经节阻滞剂六甲铵消除了对高碳酸血症的心脏反应，因此反射性心脏加速很可能是由交感肾上腺素能神经元衍生的儿茶酚胺介导的。由于它可能在暴露于高碳酸血症的过程中促进细胞内酸化，因此推测碳酸酐酶（CA）参与了CO2感测，并且抑制CA活性会钝化下游反应。实际上，在5 d.p.f时鱼类对高碳酸血症（0.75％CO2）的心脏反应降低了。暴露于乙酰唑胺（一种CA抑制剂）中，并且在经历zCAc（类似CA2的a）敲低的鱼类中。通过CA活性测量，Western印迹和免疫细胞化学证实了zCAc的成功敲除。与zCAc吗啉代和在吗啉代结合位点修饰的mRNA共同注入胚胎可以恢复正常水平的CA活性和蛋白质水平，并恢复（缓解）对高碳酸血症的常规心脏反应。这些数据与zCAc在皮肤上的NEC中表达的发现相结合，表明斑马鱼幼虫中CO2诱导的心脏反射的传入肢体是由头皮的CO2感应神经上皮细胞引发的

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