title: Calcium and cyclic adenosine monophosphate as second messengers for vasopressin in the rat inner medullary collecting duct.
abstract: Vasopressin increases both the urea permeability and osmotic water permeability in the terminal part of the renal inner medullary collecting duct (terminal IMCD). To identify the second messengers that mediate these responses, we measured urea permeability, osmotic water permeability, intracellular calcium concentration, and cyclic AMP accumulation in isolated terminal IMCDs. After addition of vasopressin, a transient rise in intracellular calcium occurred that was coincident with increases in cyclic AMP accumulation and urea permeability. Half-maximal increases in urea permeability and osmotic water permeability occurred with 0.01 nM vasopressin. The threshold concentration for a measurable increase in cyclic AMP accumulation was approximately 0.01 nM, while measurable increases in intracellular calcium required much higher vasopressin concentrations (greater than 0.1 nM). Exogenous cyclic AMP (1 mM 8-Br-cAMP) mimicked the effect of vasopressin on urea permeability but did not produce a measurable change in intracellular calcium concentration.
  
  
  CONCLUSIONS
  (a) Cyclic AMP is the second messenger that mediates the urea permeability response to vasopressin in the rat terminal IMCD. (b) Vasopressin increases the intracellular calcium concentration in the rat terminal IMCD, but the physiological role of this response is not yet known.
authors.affiliation: Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892.
authors.forename: R A
authors.initials: RA
authors.lastname: Star
authors.forename: H
authors.initials: H
authors.lastname: Nonoguchi
authors.forename: R
authors.initials: R
authors.lastname: Balaban
authors.forename: M A
authors.initials: MA
authors.lastname: Knepper
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007679:Kidney Medulla; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D009994:Osmolar Concentration; D010539:Permeability; D051381:Rats; D011919:Rats, Inbred Strains; D013047:Specific Pathogen-Free Organisms; D014508:Urea / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor; D014508:Urea; D000242:Cyclic AMP; D003894:Deamino Arginine Vasopressin; D001920:Bradykinin; D002118:Calcium