The placenta, which produces many hormones,
is not known to produce oxytocin. This
hormone is produced in the posterior pituitary
and primarily responsible for uterine contraction
claimed that she uses powdered dried sheep placenta,
administered orally, to facilitate delivery in
patients with uterine inertia.
Sisson et al. (1961) have shown that dialysates
from homogenates of rabbit placenta contain a
hypotensive-inducing, smooth muscle contracting
principle, which was later shown by Sisson (1963)
to be a polypeptide which was not oxytocin or
bradykinin. The substance, however, did not contract
the gravid rabbit uterus.
Even if the sheep placenta produced an oxytocic
peptide, it would seem unreasonable to assume
that the dried placenta could contain an active
oxytocic peptide. Nonetheless, it was decided to
investigate the possible oxytocic effects of infusions
of fresh placenta in normal saline. To our
great surprise, it was found that the infusion had
a strong oxytocic action on pregnant and nonpregnant
adult guinea-pig uteri, and that from 1 g
of the sheep placenta, an oxytocic effect equipotent
with 2.5 60 IU of oxytocin could be obtained.
Pregnant and non-pregnant rat uteri were
also stimulated, The oxytocic activity was not
affected by boiling or by autoclaving the infusion
for 15 min at 121°C at a pressure of 1.05 kg/cm 2.
It was therefore decided to examine the oxytocic
effects of normal saline extract of the pulverized
dried placenta on pregnant and non-pregnant mature
guinea-pig uterus, and on pregnant rat
uterus. The effects of heat, changes in pH of the
extract, and enzyme hydrolysis with trypsin and
pepsin on the oxytocic activity were then investigated.
The effect of the saline extract on the
intestine (guinea-pig ileum) and on the cardiovascular
system using four animal models were also
examined.