Malpighian Tubule Transport Physiology: Mechanisms and Regulation

9604394 Beyenbach昆虫肾脏的功能非常显著，因为它的尿液完全是由分泌机制产生的，而不是像人类肾脏那样通过过滤产生。分泌是由激素调节的，这样昆虫既不会水分不足，也不会水分过多。最近发现的一种激素，库仑利尿肽，可以保护昆虫免受过度水合，这对食血昆虫特别重要。蚊子吃一顿血餐时，如果不是因为极快地处理这顿饭，它的有效载荷是自己体重的两倍多，可能会威胁到飞行，造成灾难性的后果。令人惊讶的是，大量摄入的血液在进餐过程中被肾脏消化、吸收和排泄，从一端向宿主撒尿，同时从另一端吸血，雪上加霜。这样做，蚊子就会清除掉不需要的盐、水和血粉的重量，然后飞走，留下糖、脂肪和蛋白质供自己使用。肾脏中盐和水的高转运显然是由库雷克斯利尿肽激素触发的，它刺激肾脏细胞之间的转运，令人惊讶的是，也是在肾脏细胞之间！肾脏细胞之间的转运及其激素的调节是生物学中的一个新现象，对于我们理解从肾脏到肠、胃、胰腺和分泌腺的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控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.