ISSN:
1432-136X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The mechanisms underlying diuresis in the leech have been investigated. 1. The time course of the osmotic and ionic concentrations of the primary urine was measured after filling the crop with hypo- or hyperosmotic salt solutions. They were compared with data of blood and final urine, obtained earlier under the same conditions. 2. The strong diuresis after feeding is probably due to accelerating primary urine formation rather than to a decrease in reabsorption of primary urine volume. 3. The Na+ and K+ concentrations in the primary urine each show a distinct time course after hyper- or hypo-osmotic crop infusion. Cl− concentration always equals the sum of the Na+ and K+ concentrations. 4. Assuming that volume change between primary and final urine is negligible, it is calculated that primary urine secretion of Na+ is increased nearly 8 fold after hypo-osmotic crop infusion and 15 fold after hyperosmotic crop infusion, respectively, and secretion of K+ nearly 4 fold in both cases. Thus, during diuresis primary urine flow appears to be generated mainly by Na+-secretion. 5. The secretory rate of Na+, K+, and Cl− is not sensitive to the respective blood concentrations. 6. The percentage reabsorption of K+ is always higher than that of Na+. However, the percentage and real reabsorption of Na+ after hyperosmotic crop infusion is significantly lower than after hypo-osmotic crop infusion. 7. It is suggested that Na+ and K+ secretion and reabsorption are controlled by separate mechanisms.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00688719
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