Reabsorption of betaine in Henle's loops of rat kidney in vivo
| Autor: | William H. Dantzler, Yeong Hau H. Lien, Stefan Silbernagl, Gilbert W. Moeckel, Katharina Völker, Stefan Pummer |
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| Rok vydání: | 2000 |
| Předmět: |
Male
medicine.medical_specialty Proline Physiology medicine.medical_treatment Lumen (anatomy) stat Absorption Kidney Tubules Proximal chemistry.chemical_compound Betaine In vivo Internal medicine medicine Animals Kidney Tubules Distal Kidney urogenital system Reabsorption Rats Inbred Strains Sarcosine Diuresis Rats Kinetics medicine.anatomical_structure Endocrinology chemistry Biochemistry Renal physiology Loop of Henle Diuretic |
| Zdroj: | American Journal of Physiology-Renal Physiology. 278:F434-F439 |
| ISSN: | 1522-1466 1931-857X |
| Popis: | This study was designed 1) to localize and 2) to characterize betaine reabsorption from the tubular lumen in rat kidney in vivo, and 3) to test whether reabsorption is modulated by the diuretic state. [14C]betaine (+ [3H]inulin) was microperfused through the proximal convoluted tubule (PCT) and microinfused into late proximal (LP) and early distal (ED) tubules, long loops of Henle (LLH), and vasa recta of the rat in vivo et situ, and the fractional recovery of the14C label was determined endproximally (PCT) and in the final urine, respectively. [14C]betaine was not reabsorbed during ED microinfusion, whereas fractional reabsorption during LP microinfusion was 82% at 0.06 mM betaine and decreased gradually to 4.8% at 60 mM. l-Proline had lower Michaelis-Menten constant ( Km) and sarcosine a higher Kmthan betaine. Chronic, but not acute, diuresis inhibited betaine reabsorption in Henle's loops. Fractional [14C]betaine reabsorption in PCT was much smaller than that during LP microinfusion. [14C]betaine (7.28 mM) microinfused 1) into LLH was reabsorbed to 30% and 2) into vasa recta appeared in the ipsilateral urine to a much higher extent than contralaterally. In both cases, no saturation was detected at 70 mM. We conclude that betaine is reabsorbed by mediated transport from descending limbs of short Henle's loops by a proline-preferring carrier in a diuresis-modulated manner. In the deep medulla, bidirectional blood/urine betaine transport exists. |
| Databáze: | OpenAIRE |
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