title: Effect of aging on urinary concentrating mechanism and vasopressin-dependent cAMP in rats.
abstract: The effect of aging on urinary concentrating ability and the pathogenic mechanism involved were investigated in Fischer 344 rats. While the rats had free access to drinking water, 24-mo-old rats were polydipsic and polyuric compared with 6- and 12-mo-old rats. The maximum urinary concentrating ability after 40-58 h of water deprivation was not different between 6- and 12-mo-old rats (Uosmol 2,941 +/- 173 vs. 2,706 +/- 96 (SE) mosmol/kg), but it was significantly decreased in 24-mo-old rats (1,885 +/- 172 mosmol/kg, P less than 0.01). Similarly, although 5 mU/ml vasopressin increased the concentration of cAMP and papillary slices in 12-mo-old rats (delta +2.81 +/- 0.62 pmol/mg tissue, P less than 0.01), the same concentration of vasopressin failed to increase the cAMP concentration in 24-mo-old rats (delta +0.25 +/- 0.21 pmol/mg tissue, P greater than 0.05). In the adenylate cyclase preparation of renal papilla, the response to low concentrations of vasopressin was diminished in 24-mo-old rats. The dose-response curve was shifted to the right and the ED50 concentration of vasopressin was increased in 24-mo-old rats compared with 12-mo-old rats: 1.40 +/- 0.12 mU/ml vasopressin vs. 3.04 +/- 0.22. These results suggest that the decrease in vasopressin-dependent cAMP generation may in part be responsible for the impairment of urinary concentrating ability in 24-mo-old rats.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000375:Aging; D000818:Animals; D001696:Biomechanical Phenomena; D000242:Cyclic AMP / Q000032:analysis / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D007671:Kidney Concentrating Ability; D007679:Kidney Medulla / Q000032:analysis; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D011916:Rats, Inbred F344; D012964:Sodium / Q000652:urine; D014667:Vasopressins / Q000494:pharmacology*; D014868:Water Deprivation
chemical_list: D014667:Vasopressins; D012964:Sodium; D000242:Cyclic AMP; D000262:Adenylyl Cyclases