Diabetes insipidus, pathological endocrine condition characterized by excessive thirst and excessive production of very dilute urine.
They also produce large quantities of very dilute urine to excrete excess water that diffuses into their bodies (Figure 8).
In fresh water they suffer entry of water by osmosis, which is counteracted by the excretion of a large volume of dilute urine.
This is the case, for example, in their ability to concentrate and dilute urine and to achieve a gradient of hydrogen ions between urine and blood.
To compensate, the kidney (which has large glomeruli) produces a relatively large amount of dilute urine (about 20 percent of the body weight per day).
In certain disorders of the pituitary in which ADH secretion is diminished or absent e.g., diabetes insipidus there may be a fixed and irreversible output of a large quantity of dilute urine.
In early pregnancy, secretion of large amounts of dilute urine of decreased acidity, together with pressure of the uterus on the bladder, causes frequency of urination and nocturnal voiding.
Nitrogenous excretion is no problem: some ammonia is carried away in the large volume of dilute urine, but most of it simply escapes to the external medium by diffusing through the gills.
At the championships themselves, four Chinese swimmers tested positive for a banned diuretic (used to dilute urine samples so that anabolic steroids are not detected).Are such results proof that the system is working, that top-level sport is becoming cleaner?
The quantitative loss of nephrons can account for the majority of the changes observed in chronic renal failure; the failure in excretion is due directly to loss of glomerular filters, and other features such as the large quantities of dilute urine represent a change in tubular function that could be accounted for by the increased load that each remaining nephron has to carry.
This results in a reduction of the kidneys' capacities to preserve free water, leading to impaired concentrating ability and the production of excessively dilute urine (Gitlin 1999).
