Nishimura H, Imai M
Fed Proc. 1982 Jun;41(8):2355-60.
The glomerular filtration rate (GFR) of teleost fishes is highly variable and is influenced by glomerular intermittency, environmental salinity, renal perfusion pressure, and some hormones. In freshwater (FW) teleosts, the primary function of the kidney is to excrete excess water while retaining most of the filtered solutes, and GFR is a major determinant of urine flow. Low permeability to water prevails in the distal nephron of FW teleosts, and the majority of the filtered Na and Cl is reabsorbed without osmotic accompaniment of water. Prolactin appears to regulate osmotic permeability to water. Isolated and perfused distal tubules from FW teleosts revealed a transepithelial voltage (Vt) that was positive in the lumen. Both Na and Cl participate in generating lumen-positive Vt. Marine teleosts, which are exposed to Na loading and dehydration, ingest seawater to compensate for their osmotic water loss, and secrete divalent ions, mainly Mg and SO4, from the kidney. The urine flow of marine teleosts is primarily determined by fluid secretion accompanied by divalent ions and subsequent isosmotic reabsorption with NaCl. Interdependence of Na and Cl transport has been noted in the urinary bladder of marine teleosts. There is presently no known humoral substance that regulates NaCl and divalent ion transport in the teleost kidney.
硬骨鱼类的肾小球滤过率（GFR）变化很大，受肾小球间歇性、环境盐度、肾灌注压和一些激素的影响。在淡水硬骨鱼类中，肾脏的主要功能是排出多余的水分，同时保留大部分滤过的溶质，而GFR是尿流的主要决定因素。淡水硬骨鱼类远曲小管对水的通透性较低，大部分滤过的钠和氯在没有水的渗透伴随下被重吸收。催乳素似乎调节对水的渗透通透性。来自淡水硬骨鱼类的分离并灌注的远曲小管显示出管腔内为正的跨上皮电压（Vt）。钠和氯都参与产生管腔内正的Vt。海洋硬骨鱼类面临钠负荷和脱水问题，它们摄入海水以补偿渗透性水分流失，并从肾脏分泌二价离子，主要是镁和硫酸根。海洋硬骨鱼类的尿流主要由伴随二价离子的液体分泌以及随后与氯化钠的等渗重吸收决定。在海洋硬骨鱼类的膀胱中已注意到钠和氯转运的相互依赖性。目前尚无已知的体液物质调节硬骨鱼类肾脏中的氯化钠和二价离子转运。
