Effects of various ambient temperatures and of heating and cooling the hypothalamus and cervical spinal cord on antidiuretic hormone secretion and urinary osmolality in pigs.

Abstract

SUMMARY1. Plasma ADH concentration, urinary and plasma osmolality and -haematocrit were measured in young pigs placed in cold, thermoneutral, warm and hot ambient temperatures. In some experiments a thermode placed in the hypothalamus or over the cervical spinal cord was heated or cooled at various ambient temperatures.2. Plasma ADH concentration remained at a low level (0.5-5 ,uu. ml.-') over 2 hr or 3 hr periods when the pigs were in cold, thermoneutral or warm ambient temperatures. A hot environment, which caused a marked rise in the pigs' rectal temperature, was associated with a large rise in plasma ADH level.3. The rise in plasma ADH level which occurred during an increase in body temperature was consistently and completely suppressed by simultaneous cooling of the thermode in the pre-optic region to 5 or 10°C. When the thermode was in the region of the supraoptic nucleus the rise in ADH was only partly suppressed, and when it was over the cervical cord it was only sometimes suppressed. 4. Cooling the thermodes in any position at a cold or thermoneutral ambient temperature, or heating them at a thermoneutral or warm ambient temperature, caused no consistent change in ADH.5. A diuresis, with a urinary flow-rate of at most 1 ml. min-and minimal urinary osmolality of 53 m-osmole kg-', was observed on only three occasions, twice during cooling of a thermode in the hypothalamus and once after the end of a period when the thermode was heated. In each case, the plasma ADH was less than 2 /su. ml.-'.M. L. FORSLING AND OTHERS 6. A slight rise of haematocrit in cold ambient conditions and a slight fall in the warm were observed. Otherwise changes in haematocrit were trivial, and a shift of water between vascular system and interstitium could not be invoked to account for changes in ADH levels. Observed variation of plasma osmolality was also slight.

Responses of the Pituitary‐adrenal System of the Pig to Environmental Changes and Drugs

“…In these pigs the plasma concentration of ADH was measured in addition to the corticosteroid concentration. As can be seen in Figure 11, when the thermode was cooled the rise in corticosteroids in an ambient temperature of 43°C still occurred, but the rise in ADH which is normally seen on exposure to heat (Forsling et al, 1976) (compare Figure 10) In the present work the sensitivity of the pituitaryadrenal system of the domestic pig and the consistency of its response to disturbances in the environment of the animal has been tested.…”

“…Figure 8 shows the results of yet another experiment in which a pig was exposed to -5°C. In this case the plasma ACTH concentrations were measured by the radioimmunoassay as well as Figure 8 Effect of a cold environment (-5 In two other piglets figures were also obtained for the plasma concentration of ADH (Forsling et al, 1976). Both the plasma concentrations of ADH and corticosteroids increased on exposure to heat ( Figure 10); the ADH retumed to the control value sooner than the plasma corticosteroids.…”

“…Antidiuretic hormone (ADH) was measured by bioassay on waterloaded rats as described by Forsling (1974). Some of the ADH values discussed in the present paper have been published previously (Forsling, Ingram & Stanier, 1976 [3H]-cortisol (2 pCi/pig) was injected through one indwelling catheter in a volume of 3 ml saline and washed in with 5 ml saline. Blood samples were then taken from the second indwelling catheter in the contralateral jugular vein.…”

Integration of thermal and osmotic regulation of water homeostasis: the role of TRPV channels

“…In addition to hyperosmolality and hypovolemia and/or hypotension, an increase in hypothalamic temperature also stimulates VP secretion and thirst (27,28,77). Classic studies from the laboratory of Andersson (3, 4) using thermodes to locally heat and cool the preoptic-anterior hypothalamic area in the goat demonstrated that increasing and decreasing the temperature enhanced and inhibited drinking, respectively.…”

Effect of cooling on supraoptic neurohypophysial neuronal activity and on urine flow in the rat.

“…Decreased levels of this hormone have been reported in humans (Segar & Moore, 1968) and rats (Morgan, Anderson, Ellis & Berl, 1983), whereas increased levels in unanaesthetized dogs (Sadowski et al 1972) and no consistent changes in young pigs (Forsling et al 1976) have been observed.…”