Endogenous lithium clearance as a probable measure of end-proximal fluid delivery in the amphibian kidneys: a study of renal water and Na+ reabsorption in the hydrated and dehydrated frog Rana temporaria.
In fully hydrated frogs (R. temporaria) a clearance of endogenous lithium (CLi) coincides with the glomerular filtration rate (CCoEDTA) which is on average 32 ml/kg/hr, i.e. fractional lithium excretion (FELi) is close to unity, and urine to plasma concentration ratios (U/P) of Li+ and 57Co-EDTA are about 1.4. On average, in severely dehydrated frogs CCoEDTA decreases to 6.2 ml/kg/hr, CLi to 2.4 ml/kg/hr, and (U/P)CoEDTA and (U/P)Li rise to 8.4 (max = 15.2) and 3.2 (max = 5.5), respectively. FELi makes about 0.4, i.e. in these animals, rather than in well hydrated ones, a noticeable lithium reabsorption in the kidney-urinary bladder complex is observed. Obtained data are discussed from the point of view that in amphibian kidneys (as in mammalian ones) the lithium clearance may serve as a measure of end-proximal fluid delivery and observed reabsorption of Li+ in the total kidney-urinary bladder complex in fact characterizes the reabsorption of Na+ and H2O in the proximal tubule.
Fleishman
D G
DG
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Sankt-Petersburg.
Nikiforov
V A
VA
Saulus
A A
AA
Vasilieva
V F
VF
D000818:Animals; D001834:Body Water / Q000378:metabolism*; D003037:Cobalt Radioisotopes; D003681:Dehydration / Q000378:metabolism*; D004492:Edetic Acid / Q000493:pharmacokinetics; D005919:Glomerular Filtration Rate / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008094:Lithium / Q000097:blood / Q000378:metabolism* / Q000652:urine; D011896:Rana temporaria / Q000502:physiology*; D012964:Sodium / Q000097:blood / Q000378:metabolism* / Q000652:urine
D003037:Cobalt Radioisotopes; D008094:Lithium; D004492:Edetic Acid; D012964:Sodium