Göransson Viktoria, Johnsson Cecilia, Nylander Olof, Hansell Peter
Division of Integrative Physiology, Department of Medical Cell Biology, Biomedical Centre, Uppsala University, Uppsala, Sweden.
J Physiol. 2002 Jul 1;542(Pt 1):315-22. doi: 10.1113/jphysiol.2001.014894.
Our previous studies in rats have suggested a role for renomedullary hyaluronan (HA) in water homeostasis. The gerbil is known for its unique ability to conserve water. In the present study renal papillary and intestinal HA were compared between groups of anaesthetized gerbils and rats before and after up to 6 h of I.V. water loading. Baseline papillary HA in gerbils was only 37 % of that in the rat. Water loading in rats increased the papillary HA content. Elevation was maximal (+27 %, P < 0.05) after 2 h of water loading and then declined to control levels after 6 h of water loading (+3 %, n.s.). In contrast, the gerbil responded with a decreased papillary HA content during water loading. The depression was maximal after 2 h (-49 %, P < 0.05) and was still 41 % below the control values after 6 h (P < 0.05). The urine flow rate increased rapidly in the rat and its maximum, 21 times above the control level (P < 0.05), occurred at the HA peak, i.e. after 2 h of water loading while in the gerbil, the urine flow rate increased slowly and slightly and was only six times above control values after 6 h of water loading (P < 0.05). The HA content along the intestine was similar in the two species: lowest in the duodenum and jejunum and highest in the distal colon. To conclude, in the rat, the elevation of papillary interstitial HA during acute water loading would counteract water reabsorption by changing the physico-chemical characteristics of the interstitial matrix favouring rapid water diuresis. This would work as a complement to the powerful regulation by ADH. The gerbil has a diametrically different regulation of papillary HA turnover during water loading. The decreased papillary HA level during water loading and the slow and small diuretic response may represent a genetic difference in adaptation to enhance the ability to conserve water in an arid environment.
我们之前在大鼠身上进行的研究表明，肾髓质透明质酸（HA）在水稳态中发挥作用。沙鼠以其独特的节水能力而闻名。在本研究中，对麻醉后的沙鼠和大鼠进行分组，比较静脉注射水负荷长达6小时前后肾乳头和肠道中的HA。沙鼠的基线乳头HA仅为大鼠的37%。给大鼠进行水负荷会增加乳头HA含量。水负荷2小时后升高幅度最大（+27%，P<0.05），然后在水负荷6小时后降至对照水平（+3%，无统计学意义）。相比之下，沙鼠在水负荷期间乳头HA含量降低。2小时后降低幅度最大（-49%，P<0.05），6小时后仍比对照值低41%（P<0.05）。大鼠的尿流率迅速增加，其最大值比对照水平高21倍（P<0.05），出现在HA峰值时，即在水负荷2小时后；而沙鼠的尿流率增加缓慢且幅度较小，水负荷6小时后仅比对照值高6倍（P<0.05）。两种动物肠道中的HA含量相似：十二指肠和空肠中最低，远端结肠中最高。总之，在大鼠中，急性水负荷期间乳头间质HA的升高会通过改变间质基质的物理化学特性来促进快速水利尿，从而抵消水的重吸收。这将作为抗利尿激素强大调节作用的补充。沙鼠在水负荷期间对乳头HA周转的调节截然不同。水负荷期间乳头HA水平降低以及利尿反应缓慢且幅度较小，可能代表了一种遗传差异，有助于在干旱环境中增强节水能力。
