Abstract
The water (intestinally) and salt (intravenously) loads of a sufficient intensity (about 120 ml water or 9 mmol NaCl per kg body mass) caused a reversible conversion (of duration of 30–40 min) in the renal Li transport, i.e., transition from net reabsorption of this ion (FELi = CLi/GFR 1), where CLi—lithium clearance, GFR—glomerular filtration rate, 65ZnDTPA clearance. Maximal values of the fractional lithium excretion (FELi) amounted to about 1.5 and 2.0 after the water and salt loads, respectively. A repeated salt load (4–5 NaCl injections by 9 mmol/kg at 20–40 min intervals) induced a long (2–3 h) net secretion of lithium in the chicken kidney. This regime of renal functioning was characterized by abundant urination (20–30 ml/kg/h) and a substantial increase of the Na+ concentration in blood plasma (from 138 ± 9 to 172 ± 10 mM, the mean ( standard deviation) and in urine (to 157 ± 19 mM). The data obtained were considered in terms of a hypothesis suggesting that the renal lithium secretion indicates the appearance of net water and Na+ secretion in the proximal tubule of the avian kidney in response to water and salt load. The fractional reabsorption of Na+ and water in the chicken kidney were calculated by means of lithium clearance during both the net reabsorption and the secretion of lithium in the kidney. In the former regime of renal functioning (FELi 1, the fractional reabsorption of Na+ and water decrease significantly: the minimal values amount to about 60%, while the mean values, about 80%.
Published Version
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