The selective appetite for Na⁺ shown by Na⁺‐deficient sheep

Abstract

In view of the importance of Na+ equilibrium to normal function of higher species, an innate behaviour pattern promoting its intake in the face of deficiency could give an important survival advantage to the organism. Richter (1956) has shown that young rats, for whom their mother's milk has been the sole source of nourishment, consistently showed an active appetite for NaCl when confronted with it for the first time. He states that with mammals there is a universal liking for NaCl, and he considers this to be indicative of an inherited behaviour pattern which has conferred survival advantage. This primitive attraction for salt was modified by metabolic conditions, as is evidenced by the increased intake of NaCl solution which occurred when NaCl loss was caused by adrenalectomy.Previous publications from this laboratory have described the preparation and maintenance of sheep which have a permanent unilateral parotid fistula (Denton, 1956(Denton, , 1957 a; Denton, Goding & Wright, 1959), and lose 1-41./day of alkaline parotid saliva containing 170-680 m-equiv of NaHCO3. An animal prepared in this manner is an excellent subject for the study of physiological adaptations in the face of a controlled and precisely defined stress on the milieu interieur. This paper reports experiments on the voluntary intake by sheep of Na-containing solutions, and the effect of Na+ deficiency caused by loss of saliva on this voluntary intake. METHODSTwenty sheep of Merino or Merino cross-breeds were used. Six were ewes, the remainder were wethers. They were 1-7 years old. Apart from the normal sheep in Table 1 all had Wright-type permanent unilateral parotid fistulae and ipsilateral carotid artery loops. A number had contralateral carotid artery loops also. Three sheep, T.P. 1, T.P. 4, and T.P. 12, had the left adrenal gland transplanted to a combined carotid-artery-jugular-vein skin loop in the neck (McDonald, Goding & Wright, 1958) and the right adrenal gland removed.Most of the sheep were purchased from sale yards, and their previous history was unknown in relation to the possibility of access to salt licks or to bore water containing salt. The animals were kept in stainless-steel metabolism cages which effectively separated excreta, 7 PHYSIO. CLVII

The Effect of Aldosterone, Cortisol, and Corticosterone Upon the Sodium and Potassium Content of Sheep's Parotid Saliva*

“…The animals were allowed 0.4 kg oaten chaff and 0.4 kg lucerne chaff per day with a Na content of approximately 100 mEq per day. All animals were housed in metabolism cages, and had free access to water and sodium bicarbonate solution except during Na depletion (13). Voluntary Na intake and volumes of saliva and urine were recorded daily.…”

Studies of the Control of Plasma Aldosterone Concentration in Normal Man

“…For example, the sheep has an exquisitely sensitive salt appetite so that a sodium deficit is both precisely and rapidly corrected when a sodium solution is offered (23). This is uncommon in normal man.…”

Arousal of a specific and persistent sodium appetite in the rat with continuous intracerebroventricular infusion of angiotensin II.

“…It was first described by Richter (1936) in the adrenalectomized rat and is induced, we know now, by a variety of challenges (Denton & Sabine, 1961;Falk, 1961;Fregly & Waters, 1966;Stricker, 1973;Wolf, 1964), some of which occur naturally (adrenal insufficiency, Na deprivation) others of which are inventions of the laboratory (i.P. dialysis, parotid fistulation, s.c. trauma with formalin, treatment with frusemide and other diuretics), all of which have in common a reduction of plasma Na.…”