Kinetics of urea and water permeability activation by vasopressin in rat terminal IMCD.

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Wall SM, Han JS, Chou CL, Knepper MA

Kinetics of urea and water permeability activation by vasopressin in rat terminal IMCD.

Am J Physiol. 1992 Jun;262(6 Pt 2):F989-98.

PubMed ID

1320335 [ View in PubMed

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Abstract

The vasopressin-regulated urea carrier and the vasopressin-regulated water channel are distinct transporters present in the apical membrane of the inner medullary collecting duct (IMCD) cells. To assess whether these transporters may be activated by common mechanisms, we investigated the time course of increase of urea and water permeability in response to vasopressin in isolated perfused terminal IMCD segments. The permeability responses were determined through the use of a specially designed continuous-flow fluorometer for rapid analysis of collected tubule fluid samples. The time courses of activation of the two transporters by vasopressin were virtually identical. Both urea and water permeability displayed a rapid initial increase for the first 10 min followed by a slower secondary response lasting at least 30 additional min. The lag periods between vasopressin addition and the initial rise in permeability were the same for urea (34.2 +/- 8.8 s) and water (34.8 +/- 8.9 s) transport activation. Furthermore, the initial rate of permeability increase (normalized by the total increase) was not significantly different for the two transport processes. The lag periods for the increase in urea permeability in response to 8-bromoadenosine 3',5'-cyclic monophosphate and vasopressin were not significantly different. The results are consistent with the view that the rate-limiting step in vasopressin-induced activation is the same for both the urea carrier and water channel and may lie at a step beyond generation of adenosine 3',5'-cyclic monophosphate.

DrugBank Data that Cites this Article

Drug Transporters

Drug	Transporter	Kind	Organism	Pharmacological Action	Actions
Urea	Urea transporter 2	Protein	Humans	Unknown	Substrate	Details