The Effect of Vasopressin (Pitressin) Administration on Sodium, Potassium and Urea Excretion in Rats With and Without Diabetes Insipidus (Di), With a Note on the Excretion of Vasopressin in the Di Rat

Abstract

The effect of the administration of vasopressin as subcutaneous Pitressin Tannate in oil (PTO) was studied in the Brattleboro rat. Rats with hereditary hypothalamic diabetes insipidus (DI), and rats heterozygous for this abnormality, were used. A minimum dose of 1000 mu. of PTO/24 h was necessary to restore the urinary volume and osmolality of DI rats to values comparable with those of heterozygous rats. The urinary excretion of antidiuretic activity in DI rats was shown to be related to the dose of PTO. Sodium and urea excretion, but not potassium excretion, were reduced by up to 50 % in the DI rat. No comparable changes were produced in the heterozygous rat. The possible mechanisms of these actions of vasopressin are discussed.

The Effect of Chlorpropamide on Water Balance in Pitressin‐treated Brattleboro Rats

“…It is interesting to note that the administration of various doses of Pitressin to the polydipsic heterozygous rat induced decreases in fluid intake (see Fig. 2) comparable to the decreases in urine volume observed in DI rats (Laycock & Williams, 1973), but at the lower doses (e.g. 50 mu/24 h) the resulting decrease was greater in the DI rat (56%) than the glucosehydrated heterozygous rat (30%).…”

“…While the normal urine concentration of the heterozygous rat is generally lower than that of the Long Evans or Wistar strains of rats (usually over 2000 mosmol/kg H20) the exogenous administration of Pitressin (1000 mu/24 h) failed to increase further the urine osmolality (Laycock & Williams, 1973). However, Lee & Williams;(1972), did observe that the stimulus of 72 h dehydration to the heterozygous rat was sufficient to raise drastically the urine osmolality to a maximum value of 4560 with a mean of 3300 mosmol/kg.…”

“…It is appreciated that as the hormone was given in an oily solution it is possible that the percentage reabsorbed may be less than that assumed; ie. the excess may not be reaL However, indirect evidence which suggests that the hormone was being absorbed in sufficient quantities was provided by Laycock & Williams, (1973), who estimated the urinary excretions of 'vasopressin' in DI rats treated with various doses of Pitressin. From this good, indirect evidence, it would therefore appear that even when the hormone is administered in this manner, the polydipsic rat is relatively insensitive.…”

“…Vasopressin was administered as Pitressin tannate in oil (Pitressin, containing a mixture of porcine and bovine vasopressins in unspecified proportion). Two of the doses administered (25 and 50 mu Pitressin/24 h) were considered as submaximal from the dose-response curve obtained by Laycock & Williams, (1973). Chlorpropamide, from 10 ml vials containing 50 mg/ml, was also injected daily into the experimental animals, the injection volume being proportional to the dose.…”

Vasopressin Receptors, the Signalling Cascade and Mechanisms of Action

“…Vasopressin could act there by negative feedback following its action on the basolateral membrane of the inner medullary collecting duct (Nonoguchi et al, 1995). In particular, this effect would be possible in the presence of tubular vasopressin which is excreted in the urine in a concentration-dependent manner (Laycock and Williams, 1973).…”