UBC Theses and Dissertations
Studies of the sheep neurophypophysis during pregnancy and foetal development Vizolyi, Elizabeth
The biological activities of the neurohypophyses of pregnant and embryonic sheep, Ovis aries were studied. The levels of hormonal activities of the neurohypophyses varied with the stage of pregnancy, and were always lower than levels in the control (non-pregnant) glands. Chemical studies of the purified oxytocic and vasopressor moieties of the pregnant sheep have indicated that these agents are oxytocin and arginine vasopressin. An increase of biologically active agents of the posterior pituitary was detected concomitant with embryonic development. The amount of vasopressor activity greatly surpassed the oxytocic activity in the neurohypophyses of foetal sheep all through gestation, but the difference became smaller with the advancement of intrauterine life. Pharmacological and chemical studies indicated oxytocin and arginine vasopressin as the active peptides of the foetal neurohypophysis. In addition to these two neurohypophysial peptides characteristic of the mammals, the presence of a third peptide was indicated. Pharmacological studies indicate that this third neurohypophysial peptide of the foetuses may be arginine vasotocin, the antidiuretic principle of lower vertebrates.
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