Role of arginine vasopressin in medullary thick ascending limb on maximal urinary concentration
Kim, J.K.; Summer, S.N.; Erickson, A.E.; Schrier, R.W.
American Journal of Physiology 251(2 Pt 2): F266-F270
1986
ISSN/ISBN: 0002-9513 PMID: 3740273 Document Number: 284121
Two groups of Spraque-Dawley rats, Harlan (H) and Charles River (CR), were discovered in that the medullary thick ascending limb (MAL) had a profoundly different adenylate cyclase response to arginine vasopressin (AVP). Using these two groups of rats, we studied the correlation between AVP action on the MAL and maximal urinary concentration. AVP (10-6 M) significantly stimulated adenylate cyclase in MAL of H rats (7.4 .+-. 0.9 to 43.8 .+-. 4.6 fmol cAMP formed .cntdot. 30 min-1 .cntdot. min-1, P < 0.001) but not in CR rats (10.3 .+-. 1.4 to 12.7 .+-. 2.0 fmol cAMP formed .cntdot. 30 min-1 .cntdot. mm-1, NS). In contrast, AVP significantly stimulated adenylate cyclase of cortical, outer and inner medullary collecting tubules from both H and CR rats. Glucagon (10-6 M) significantly stimulated adenylate cyclase of MAL from both H and CR rats. After 48 h of fluid deprivation, urinary osmolality was significantly higher (P < 0.001) in the H (4,504 .+-. 399 mosmol/kg H2O, n = 14) than CR (2,840 .+-. 176 mosmol/kg H2O, n = 12) rats. This observation was not attributable to differences in creatinine clearance (CR, 1.30 .+-. 0.24; H, 1.24 .+-. 0.03 ml/min, NS, n = 4) or plasma AVP (CR, 12.75 .+-. 1.44; H, 12.38 .+-. 1.17 pg/ml, NS, n = 6) levels. These results therefore suggest that the action of AVP on the MAL, in addition to the effect on collecting tubules, is involved in maximal urinary concentration in rats.