Plasma antidiuretic hormone levels and liver vasopressin receptors in the jerboa, Jaculus orientalis, and rat

Abstract

V 1 vasopressin, angiotensin, α-adrenergic, and glucagon receptors in liver were studied on membrane fractions prepared from two groups of jerboas ( Jaculus orientalis) given dry or water-enriched diets for periods of 4 to 7 weeks, and from rats acutely treated with pharmacological amounts of arginine-vasopressin (AVP) or (1-deamino-8- d-arginine)-vasopressin (dDAVP). Tritiated (8-lysine)-vasopressin ([ 3H]vasopressin), tritiated (1-asparagine-5-valine)-angiotensin II ([ 3H]angiotensin II), tritiated dihydroergocryptine ([ 3H]DHEC), and iodinated glucagon ([ 125I]-glucagon) were used as specific labeled ligands of these receptors. The V 1 vasopressin, angiotensin, α-adrenergic, and glucagon receptors detected in both groups of jerboas were identical to receptors found in rat liver plasma membranes in regard to the apparent dissociation constants for their respective labeled ligands. Furthermore, vasopressin receptors in jerboa liver membranes discriminated as efficiently as rat liver receptors between the natural neurohypophyseal peptides arginine-vasopressin and lysine-vasopressin on the one hand and the structural analogs (1-deamino-8- d-arginine)-vasopressin and (4-valine-8- d-arginine)-vasopressin on the other. The reduction of antidiuretic hormone (ADH) secretion in jerboas fed a water-enriched diet compared to those on a dry diet (76 ± 25 p M versus 372 ± 86 p M) was accompanied by an increase in the number of liver vasopressin receptors (2.79 ± 0.53 versus 1.25 ± 0.14 pmol [ 3H]vasopressin bound/mg protein). The modifications observed were specific for vasopressin receptors, as judged by the maximal binding capacities of [ 3H]angiotensin II, [ 3H]DHEC, and [ 125I]-glucagon, which remained unchanged in jerboas whatever the levels of endogenous circulating ADH. Similarly, administration of pharmacological doses of AVP by iv infusion to rats induced, 2 hr later, a loss of about 50% of V 1 liver vasopressin receptors, while the numbers and apparent dissociation constants of angiotensin, α-adrenergic, and glucagon liver receptors remained unchanged, and V 2 kidney vasopressin receptors were almost desensitized. For V 1 liver and V 2 kidney vasopressin receptors, the desensitization process was strikingly dependent on the antidiuretic/glycogenolytic activity ratio of the peptide used. Thus, im injection to rats of dDAVP (an analog possessing a very high antidiuretic/glycogenolytic activity ratio) induced, 1 hr later, a total loss of V 2 kidney receptors without modification of the number and apparent dissociation constant of V 1 liver receptors.