The distribution of hypothalamic peptidases in pregnant and non-pregnant dogs.

Abstract

It appears to be generally accepted that oxytocin and vasopressin are synthesized in the hypothalamus and stored in the neurohypophysis. A variation in the hormone content of the neurohypophysis in physiological conditions involving the release of large amounts of oxytocin or vasopressin might be expected. For example, it has been established that dehydration and lactation deplete the neurohypophysis of hormones or neurosecretory material (for references see Ortmann, 1960). Some change in the metabolism of oxytocin might be expected during pregnancy. However, the concentration of hormones in pituitaries of pregnant rats did not differ greatly from that found in non-pregnant animals (Acher, Chauvet & Olivry, 1956). In view of this observation, it was decided to find out whether or not the hypothalamic enzymes inactivating oxytocin (Hooper, 1962) varied during pregnancy, for, if this were the case, it would appear probable that the metabolism of oxytocin in the hypothalamus changed during pregnancy. The present paper describes the intracellular distribution of hypothalamic enzymes inactivating oxytocin in a series of pregnant and non-pregnant dogs, and discusses certain points arising from the observed distribution patterns.