Ovine maternal and fetal renal vasopressin receptor response to maternal dehydration.
OBJECTIVE
Arginine vasopressin secretion increases in response to increased plasma osmolality or hypovolemia. Dehydration-induced increases in plasma arginine vasopressin levels have been shown to down-regulate arginine vasopressin V2 receptors in adult rat kidneys. Our study determined ovine maternal and fetal renal arginine vasopressin receptor characteristics and receptor response to maternal dehydration.


METHODS
Eight pregnant ewes (113 +/- 1 days) were dehydrated for 72 hours; eight animals served as controls. Renal medullary tissue was isolated from maternal and fetal kidneys, and arginine vasopressin receptor characteristics determined with saturation and competition assays using tritiated arginine vasopressin, arginine vasopressin, and arginine vasopressin analogs.


RESULTS
Euhydrated maternal and fetal renal medullary arginine vasopressin receptor dissociation constant (3.0 +/- 0.3 and 1.9 +/- 0.3 nmol/L) and maximal binding capacity (149 +/- 15 and 111 +/- 33 fmol/mg protein) values were similar. Pharmacologic profiles with selective agonists indicated a predominance of V2 receptors. Dehydration significantly increased maternal and fetal plasma osmolalities (304 +/- 2 to 320 +/- 2; 296 +/- 1 to 319 +/- 3 mOsm/kg water, respectively) and arginine vasopressin levels (3.8 +/- 1.4 to 29.3 +/- 4.6; 4.4 +/- 1.0 to 16.9 +/- 5.0 pg/ml, respectively) but had no effect on arginine vasopressin receptor binding.


CONCLUSIONS
Specific, saturable, single-site tritiated arginine vasopressin binding is present in ovine maternal and fetal renal medullary membranes. Ovine maternal and fetal renal arginine vasopressin receptors do not down-regulate in response to dehydration-induced elevations in plasma arginine vasopressin levels.
Kullama
L K
LK
Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center, UCLA School of Medicine, Torrance 90502.
Ross
M G
MG
Lam
R
R
Leake
R D
RD
Ervin
M G
MG
Fisher
D A
DA
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D003681:Dehydration / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005260:Female; D005333:Fetus / Q000378:metabolism*; D007668:Kidney / Q000196:embryology / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000378:metabolism*; D012016:Reference Values; D012756:Sheep
D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin