Malpighian Tubule Transport Physiology: Mechanisms and Regulation

[604394]贝恩巴赫昆虫肾脏的功能是显著的，因为尿液完全由分泌机制产生，而不像人类肾脏那样通过过滤。分泌是由激素调节的，因此昆虫既不缺水也不缺水。最近发现的一种激素，库利尿肽，可以防止昆虫过度水化，这对吸血昆虫尤其重要。蚊子摄取的血是其体重的两倍多，如果不是以极快的速度处理这顿血，就会威胁到飞行的灾难性后果。令人惊讶的是，大部分被摄入的血液在进食过程中就已经被消化、吸收并从肾脏排出，结果是一边在宿主身上小便，一边在宿主身上吸血，这是雪上加霜。这样，蚊子就能排出不需要的盐、水和血粉的重量，然后把糖、脂肪和蛋白质留给自己使用。高速率的盐和水在肾脏中的运输显然是由激素利尿肽触发的，它刺激通过肾脏细胞的运输，令人惊讶的是，也在肾脏细胞之间！肾细胞间的转运及其受激素调节是生物学上的一个新现象，对于我们理解从肾到肠、胃、胰腺和分泌腺等所有上皮细胞的转运功能具有潜在的重要意义。了解细胞间上皮运输的机制和调节的潜在生物医学和临床应用是不可否认的。

9604394 Beyenbach The function of insect kidneys is remarkable in that urine is produced entirely by secretory mechanisms and not by filtration as in human kidneys. Secretion is regulated by hormones such that the insect is neither under- nor over-hydrated. One recently discovered hormone, Culex-diuretic peptide, protects the insect against over-hydration, particularly important for blood-feeding insects. Taking a blood-meal, the mosquito takes on a payload more than twice its own body weight threatening flight with disastrous consequences were it not for extremely fast processing of the meal. Astonishingly, much of the ingested blood is digested, absorbed and excreted from the kidney while the meal is still in progress with the effect of urinating on the host from mne end while sucking blood from the other end, adding insult to injury. Doing so, the mosquito gets rid of the unwanted salt, water and weight of the blood meal and then flies away keeping sugars, fats, and proteins for its own use. High rates of salt and water transport in the kidney apparently are triggered by the hormone Culex-diuretic peptide which stimulates transport through the cells of the kidney and, surprisingly, also between the cells of the kidney! Transport between the cells of kidney and its regulation by a hormone is a new phenomenon in biology with potentially important lessons for our understanding of tranpsort functions in all epithelia, from kidney to intestine, stomach, pancreas, and secretory glands. Potential biomedical and clinical applications of understanding the mechanism and regulation of epithelial transport between cells cannot be denied.