Colchicine blocks the action of parathyroid hormone but not nicotinamide on renal phosphate transport |
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Authors: | R A Bacon K I Wu A L Ying S A Kempson |
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Institution: | Department of Physiology and Biophysics, Indiana University Medical School, Indianapolis. |
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Abstract: | Nicotinamide, like parathyroid hormone, is a rapidly acting specific inhibitor of Na+-dependent transport of phosphate (Pi) across the brush-border membrane of the proximal tubule of the mammalian kidney. Pretreatment of rats with colchicine (0.7 mg/kg body weight) for 1 h led to a significantly diminished phosphaturic response to parathyroid hormone (synthetic 1-34 fragment, 4 micrograms/kg). In contrast, the same dose of colchicine had no effect on the renal response to nicotinamide (1.0 g/kg), measured both as the change in urinary Pi excretion and as Na+-dependent Pi uptake by isolated brush-border membrane vesicles. These data suggest indirectly that the intracellular mechanism that mediates the inhibitory effects of nicotinamide on renal Pi transport does not require intact microtubules. |
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