Effects of Adrenalectomy and Hypophysectomy on Water and Electrolyte Metabolism in Male and Female Rats With Inherited Hypothalamic Diabetes Insipidus (Brattleboro Strain)

Abstract

Observations on water and electrolyte metabolism after hypophysectomy or adrenalectomy, in male and female rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain) are confirmed and extended. The diabetic (homozygous, DI) state relative to the non-diabetic (heterozygous, non-DI) state was characterized by (1) water intake of 55-120% body weight; (2) copious urine hypo-osmotic to plasma; (3) greater excretory rates of total solute, Na, Ca and Mg; (4) similar plasma composition except that in male DI rats, K concentration was less, and in female DI rats osmolarity was higher; (5) glomerular filtration rates (GFR) were similar with close correlations between: food and water intakes, water intake and output, urinary Na and K, Na and Cl, K and Cl, and Ca and Mg; (6) both female DI and non-DI rats had lower urinary Na:K ratios and lower plasma Na concentrations than males; (7) female DI rats excreted relatively larger amounts of K and Cl, and had higher plasma Ca concentrations than other groups. Hypophysectomized DI rats had decreased water intake and urine output, decreased solute excretion, decreased loss of osmotically free water, lower excretory rates of Na, K and Cl, and increased urinary osmolarity and K concentrations. Hypophysectomized non-DI rats had increased urinary excretory rates, decreased solute excretion (by 60-70%), decreased osmotically free water absorption, decreased urinary osmolarity, Na and K concentrations, and increased excretory rates of Ca and Mg. Hypophysectomized DI and non-DI rats had increased plasma osmolarity and Na concentration. Plasma renin activities (PRA) were higher in DI than in non-DI rats with female values lower than those of males; values for both sexes of DI and non-DI rats were reduced after hypophysectomy. Adrenalectomized DI rats had about a 50% reduction in water intake, urine output and free water clearance, increased urinary concentration of electrolytes and total solute by day 4 after operation; their Na balance (dietary:urine) did not change significantly in contrast to adrenalectomized non-DI rats in which a greater percentage of dietary Na appeared in the urine. GFR was similarly reduced in adrenalectomized DI and non-DI rats. Plasma osmolarity increased in adrenalectomized male DI, decreased in female DI and non-DI, and did not change in male non-DI rats. Plasma K concentrations increased after adrenalectomy in all groups, only non-DI rats had a significantly decreased plasma Na concentration. There was no sex difference in pituitary oxytocic activity but it was consistently reduced in DI rats; there was little change after adrenalectomy in male DI and non-DI rats; but there was an increase in DI and non-DI females. Pituitaries of DI rats had no measurable ADH activity (except the inherent activity of oxytocin). Pituitary ADH values for male and female non-DI rats were similar and were unaffected by adrenalectomy.

Production of Aldosterone in Male Rats with Inherited Diabetes Insipidus (Brattleboro Strain)

“…While, Balment, Henderson and Chester Jones (1974) found that plasma potassium concentration of DI rats was higher than those of control rats, our results confirm the previous observations of a slight reduction of kaliemia in homozygous Brattleboro rats of Mohring et al (1974) and Balment, Chester Jones, Henderson and Oliver (1976).…”

Renal and blood pressure changes in response to vasopressin antagonism in the New Zealand genetically hypertensive rat

“…A similar natriuresis is presented by the Brattleboro DI rat, which normally excretes more (up to 60%) sodium than Long Evans or AVPreplete DI hétérozygote rats (Laycock & Williams 1973;Balment et al 1976). The apparent fall in cir¬ culating aldosterone may also contribute, in part, to the loss of sodium by these animals.…”

Influence of captopril on fluid and electrolyte balances and adrenocortical responses during sodium deprivation in the rat

“…Water and electrolyte balances and adrenocortical function Daily (24-h) food and water intakes and urinary excretory rates were measured in individual rats held in all-glass metabolism cages (Metabowl; Jencons, Hemel Hempstead). Animals were acclimatized to the cages for 7 days before measurements were begun (Balment, Chester Jones, Henderson & Oliver, 1976).…”

“…Grouped data were compared by Student's /-test and data from the metabolism cage studies by a paired /-test (see Balment et al 1976). …”