Actions of NAD+ on renal brush border transport of phosphate in vivo and in vitro
| Autor: | S. T. Turner, Ahad N.K. Yusufi, Thomas P. Dousa, Stephen A. Kempson |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
Glycerol
Male Proline Brush border Physiology Renal cortex Biological Transport Active Fructose Phosphates Kidney Tubules Proximal chemistry.chemical_compound Non-competitive inhibition In vivo medicine Animals Microvilli Nicotinamide Rats Inbred Strains NAD In vitro Rats Kinetics medicine.anatomical_structure chemistry Biochemistry NAD+ kinase |
| Zdroj: | American Journal of Physiology-Renal Physiology. 249:F948-F955 |
| ISSN: | 1522-1466 1931-857X |
| DOI: | 10.1152/ajprenal.1985.249.6.f948 |
| Popis: | Previous studies showed that an increase in NAD+ content in renal cortex in vivo was accompanied by specific inhibition of Na+-dependent inorganic phosphate (Pi) transport across the renal brush border membrane (BBM). Further, in vitro addition of NAD+ to isolated renal BBM vesicles specifically inhibited Na+ gradient-dependent transport of Pi. The present study examined some aspects of the mechanism of this inhibition by NAD+ in vitro and in vivo. When NAD+ was increased in vivo by nicotinamide injection, the apparent Vmax was decreased, but the apparent Km was not different, indicating apparent noncompetitive inhibition. In the presence of 0.3 mM NAD+ added in vitro, the apparent Km for Na+-dependent Pi transport by BBM vesicles was increased, whereas the apparent Vmax was unchanged, indicating apparent competitive inhibition. These changes in apparent Km and apparent Vmax were identical when Pi uptake was measured either at 30-s or at 5-s (the initial rate) incubation times. Inhibition of Pi transport by BBM vesicles in vitro was due primarily to the action of intact added NAD+, although there may be some contribution by isotope dilution due to Pi released from NAD+ by enzymatic hydrolysis. Although in vitro inhibition of Pi transport by added NAD+ was reversed by washing the BBM, the inhibition due to increased NAD+ in vivo persisted after extensive washing of the isolated BBM. The specificity of the inhibitory effect of NAD+ in vivo was indicated by the finding that changes in renal cortical content of ATP or Pi, evoked by loading with glycerol or fructose, did not change BBM transport of Pi.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: | OpenAIRE |
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