On the Mechanism of Action of Intra-Amniotic Hypertonic Saline Treatment in Rabbits

Abstract

A study was made into the effects of hypertonic saline upon the intra-uterine pressure in non-pregnant and pregnant rabbits. In non-pregnant rabbits intra-luminal administration of hypertonic saline caused an almost immediate transient increase in amplitude and frequency of uterine pressure cycles, a response which was abolished by prior treatment with progesterone. In pregnant rabbits, provided all placentae were damaged by the treatment, intra-amniotic administration of 20% NaCl resulted in abortion of all foetuses in 56 \ m=+-\ 7\m=.\3hr SE.If one conceptus escaped damage pregnancy was not interrupted. Furthermore, treatment with 25 \g=m\g/day oestradiol propionate prevented abortion. Of the procedures carried out, only dislocation of the placentae also caused abortion, whereas pregnancy was not terminated by extra-amniotic administration of hypertonic saline, by cutting the umbilical cords (i.e. causing foetal death), nor by the intra-amniotic administration of normal (0\m=.\9%) saline. The abortion produced by both intra-amniotic hypertonic saline and dislocation of the placentae could be prevented by oestrogen administration, but not if ovariectomy were combined with placental dislocation. From these results, it is concluded that intra-amniotic hypertonic saline induced abortion in rabbits by interrupting the luteotrophic function of the placenta which resulted in loss of the luteal function essential for the defence of pregnancy.

Serum Leptin Levels in a Patient with Pheochromocytomah

“…In rabbits (and goats), the corpus luteum secretes progesterone throughout pregnancy (13), so that a disorder in placental progesterone secretion will not adversely affect the pregnancy. In these animals, placental choriogonadotropin is needed to maintain the maternal corpus luteum, but the placenta is not needed to produce progesterone (14). By contrast in human beings, the corpus luteum secretes progesterone only during the first trimester; placental progesterone becomes sufficient to maintain pregnancy only after about 6 weeks gestation; the so-called "luteoplacental shift" (13,15).…”

Identification and Preliminary Characterization of Luteotropic Activity in the Rabbit Placenta1

“…It has further been demonstrated that the fetal portion of the placenta is the most important component of the conceptus in maintaining luteal P 4 production. Removal of the fetus and placenta results in luteal regression, whereas removal of the fetus alone has no effect on P 4 production [2,[5][6][7][8]. The factor(s) produced by the conceptus that is responsible for maintaining P 4 production has not yet been fully identified or characterized, although previous investigators have reported identification of a potential placental luteotropin using a cultured luteinized granulosa cell bioassay system…”

Bilateral maintenance of rabbit corpora lutea by the feto-placental unit

“…Corpora lutea of the pregnant rabbit require the pres¬ ence of the fetal placenta to maintain progesterone production throughout pregnancy (Chu, Lee & You, 1946;Porter, Becker & Csapo, 1968;Holt & Ewing, 1974;Lanman & Thau, 1979). It is not known, however, whether the effect of the feto-placental unit is antiluteolytic and/or luteotrophic or whether it is exerted locally and/or systemically.…”