[The osmoregulating function of the kidney and activity of the loop of Henle in water rats, gerbils and Brattleboro rats].

The concentration index U-P Osm in dehydration was 7.9 in gerbil, 2.7 in water rats and 1.7 in the Brattleboro homozygote rats. The sodium content in the kidney medullar substance of the animals under study correlated with the ability for creation of the high concentration gradient U-P Osm. The sodium excretion for 100 ml of filtrate, in maximal suppression with furosemide of the Cl- ions reabsorption in the large ascending parti of Henle's loop, was practically the same in all the rodents under study. This suggests that not only the amount of reabsorbed sodium but also the morpho-functional organization of the kidney medullar substance aiding to retainment of sodium, maintain the creation of high osmotic gradient.