THE RELEASE OF POSTERIOR PITUITARY ANTIDIURETIC HORMONE BY ADENOSINE TRIPHOSPHATE

Abstract

SUMMARY: The antidiuretic effect of small doses of adenosine triphosphate has been confirmed in both the rat and the rabbit after intravenous, intraperitoneal and intramuscular injection. This action of adenosine triphosphate, which closely resembles that of 'pitressin', was shared, to a lesser degree, by related compounds possessing either a —6NH₂ or a —P₂O₇ group. The effect could not be explained in terms of pre-renal deviation of water, either by failure of absorption, or by the formation of an exudate at the site of injection. Nor could it be explained by an alteration in renal haemodynamics, since the blood pressure and glomerular filtration rate were unaffected by the intraperitoneal doses used. Noxious afferent stimuli were also excluded as causative factors. The antidiuretic action of adenosine triphosphate was inhibited by removal of the neurohypophysis and was accompanied by a fall in the antidiuretic hormone content of the posterior lobe of the pituitary. The plasma and urine of the adenosine triphosphate-treated rats contained an antidiuretic substance which behaved like 'pitressin'. In the rabbit, doses of adenosine triphosphate below the threshold for intravenous injection, caused marked changes in the rate of water excretion on intracarotid injection. The direction of the response depended on the state of hydration in the same way as the response to 'pitressin'. The antidiuretic effect of small doses of adenosine triphosphate is thought to be due to the liberation of antidiuretic hormone from the posterior lobe of the pituitary. After large doses of adenosine triphosphate the cardiovascular and the other changes accompanying the state of shock will contribute to the effect.