Fetal Neurohypophyseal Arginine Vasopressin and Arginine Vasotocin in Man and Sheep

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Abstract
Summary: Immumoreactive arginine vasopressin (AVP) and arginine vasotocin (AVT) were quantitated in 15 of 17 human fetal pituitary glands early in gestation (11–19 weeks) and in 8 of 9 ovine fetal pituitary glands late in gestation (109–137 days). In 14 of 15 human fetal glands, AVT content exceeded that of AVP. There was a significant rise of AVP (as a percentage of total AVP plus AVT content) with gestational age over the period of 12–19 weeks (P < 00.01). The ovine fetal glands demonstrated a preponderance of AVP over AVT. The mean AVP and AVT content in the ovine glands was 5.7 ± 2.9 and 0.8 ± 0.2 mU/mg gland weight, respectively, compared with the values in the human fetal pitiutarics, 0.8 ± 0.2 and 1.2 ± 0.2 mU/mg gland weight, respectively. The relative percentage of AVP and AVT in the ovine fetal pituitaries was 76.0 ± 9.6% and 23.9 ± 9.6%, respectively, as contrasted to the human fetal glands, 36.7 ± 2.7% AVP and 63.3 ± 2.7% AVT. The preponderance of AVT over AVP in the early gestational age mammalian fetus may represent a primative first step in molecular evolution of the neurohypophyseal peptides. Speculation: The results suggest that fetal neurohypophyseal vasotocin, present in early fetal life, decreases with gestational maturation, with a corresponding increase in vasopressin. Further studies are needed in the same mammalian species periodically throughout gestation to confirm this chronologic change which suggests that ontogeny recapitulates phytogeny.