Arginine vasotocin and a novel oxytocin-vasotocin-like material in plasma of human newborns.

Plasma of human adults contains an oxytocin, vasotocin-like (OT-VT) immunoreactive material that is estrogen responsive in both males and females and the levels of which are elevated during pregnancy. Although OT-VT is immunoreactive with an antiserum raised against synthetic arginine vasotocin (AVT), the elution profile of OT-VT by high-performance liquid chromatography (HPLC) is distinct from AVT, arginine vasopressin (AVP) or oxytocin (OT). Because the fetus is also exposed to high estrogen levels during pregnancy and AVT has been reported to be present in human fetal pituitaries, cord blood samples from 16 vaginally delivered human newborn infants were examined for evidence of OT-VT and AVT. Analysis of an extracted pool of cord blood plasma by HPLC revealed 4 peaks (I-IV) of AVT-like immunoreactivity. Peaks II and IV coeluted with synthetic AVP and OT, respectively, and were attributable to cross-reaction of the AVT antiserum with these peptides. Peak I was identified as AVT on the basis of its coelution with synthetic AVT. Peak III eluted in a manner identical with OT-VT. These results indicate that human newborn plasma contains at least three neurohypophysial peptides, AVP, OT and AVT. Additionally, newborn plasma contains an AVT-like immunoreactive material that is distinct from AVT, AVP and OT, but is identical with a novel OT-VT material observed in plasma of estrogen-primed adults. The physiological significance of AVT and OT-VT in newborn plasma remains to be determined.