title: Colchicine blocks the action of parathyroid hormone but not nicotinamide on renal phosphate transport.
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.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008870:Microtubules / Q000187:drug effects / Q000502:physiology; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology*; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors*; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D019379:Teriparatide
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010710:Phosphates; D019379:Teriparatide; D009536:Niacinamide; D012964:Sodium; D003078:Colchicine