Thomas R. Forbes

Maintenance of pregnancy with subcutaneous pellets of progesterone in ovariectomized mice.

Summary Mice of the CHI and Brown Belt stocks received subcutaneous pellets of 17α-hydroxyprogesterone or progesterone and then were ovariectomized at various stages of pregnancy. The average daily absorption of progesterone from the pellets which was required to ensure fetal survival to term diminished as pregnancy progressed. 17α-Hydroxyprogesterone pellets were ineffective in maintaining pregnancy in castrate mice. When the day of finding the vaginal plug was counted as day 1, duration of pregnancy in the intact untreated CHI mouse was usually 19 or 20 days. In the Brown Belt mouse, it was usually 20 or 21 days.

Inactivity of bound plasma progesterone.

Summary Pellets of crystalline progesterone implanted into the spleens of ovariectomized mice had no effect upon the endometrium despite the presence of relatively high levels of bound progesterone in the plasma; the highest level of free progesterone in these animals was 0.7 μg per ml. Subcutaneous pellets of progesterone produced characteristic progestational changes in the endometrium when the level of free plasma progesterone exceeded 1.0 μg per ml. Binding appears to be a mechanism of hepatic inactivation of progesterone in the mouse.

Plasma Progesterone Levels and the Menstrual Cycle of the Monkey.

Summary Bioassay of the free and bound plasma progesterone at various intervals through a menstrual cycle in each of 2 monkeys indicate the level of free progesterone to be low during and following menstruation, high near the middle of the cycle, lower following this peak, and high in the latter half of the cycle. A low level was present at or preceding menstruation. The levels of the bound fraction were low at all times.

Steroid compounds and the dilatation of ovarian and uterine veins in the mouse

The possible role of reproductive steroids in the vascular changes o f the estrous and menstrual cycles and of pregnancy has prompted both clinical observations and animal experiments on the influence of sex hormones on the physiology of blood vessels. Research was carried out to develop a method for exposing blood vessels of the ovariectomized mouse to the continous influence of steroids, for quantitating resulting changes in blood vessel diameter, and for evaluatin the results. The method was used for direct comparison of the effects of 10 steroid compounds. Small pellets of each of 10 steroids, or glass pellets as controls, were tied to the right uterine horns of groups of 10 ovariectomized adult virgin mice. After 7 or 21 days, the mice were killed, and the diameters of the right and left ovarian and uterine veins were measured. The largest significant increases in diameter, particularly after 21 days, were observed in mice treated with testosterone, dihydrotestosterone, estrone, estradiol-17beta, and progesterone. Lesser or no significant increases were seen in mice that had received 20-alpha-dihydroprogesterone, 20-beta-dihydroprogesterone, cholesterol, 16-alpha-hydroxyprogesterone, and 17-alpha-hydroxyprogesetrone.

Steroid Compounds, Vasodilation, and Vasoconstriction in the Mouse

Summary The response of selected major veins in the ovariectomized mouse to the implantation beside the right uterine horn of a pellet of a crystalline steroid was determined by comparing venous diameters to corresponding diameters in control mice in which glass pellets had been implanted. The left and right ovarian and uterine veins and the inferior vena cava underwent significant enlargement, particularly after treatment with estriol, androsterone, and androstenedione. The left common iliac was unresponsive. Some compounds caused decreases in the diameter of the right common iliac vein.

Steroid Pellets and Venous Diameter in Orchidectomized, Ovariectomized, and Ovariectomized-Hysterectomized Mice

Summary Pellets of most steroids impeded hair regrowth in shaved areas. Estradiol-17β caused fatal obstruction of the urinary tract in males. The diameters of the internal spermatic, ovarian, uterine, and femoral veins and the inferior vena cava in the mouse were measured in intact males, in orchidectomized males bearing glass pellets (controls) and steroid pellets, and in ovariectomized and ovariectomized-hysterectomized females with similar pellets. Mice with steroid pellets had significant increases, and sometimes significant decreases, in vein size compared to control mice with glass pellets. Venous response was greater after removal of both ovaries and uterus than after removal of ovaries only. The diameter of the internal spermatic vein appeared to depend on the influence of a steroid rather than on the presence of the testis as such.

Maintenance of pregnancy in ovariectomized and nonovariectomized mice as an index of progesterone: steroid synergism and antagonism.

Abstract The influence of endocrine factors on the maintenance of pregnancy in mice was measured in terms of fetal survival until close to term. Fetuses die promptly after maternal ovariectomy unless appropriate replacement therapy has been begun. Subcutaneous pellets of progesterone improved fetal survival rates in both intact and ovariectomized mice as compared to controls. Eleven other steroids given individually to intact mice increased, did not affect, or decreased fetal survival. When ovariectomy followed implantation of pellets of any of 14 steroids except progesterone, survival of fetuses was at or close to zero. If pregnant mice were ovariectomized after receiving pellets of mixtures of progesterone with one of 16 steroids in proportions of 1:1 and 99:1, fetal survival ranged from 15 to 93 per cent, depending on mixtures and proportions. Cholesterol and pregnanediol were nonhormonal steroids acting synergistically and antagonistically in mixtures with progesterone.

Influence of 16α-Hydroxyprogesterone, 20α-Hydroxyprogesterone and 20β-Hydroxyprogesterone on Progesterone Activity in a Bio-Assay

Summary In the B6D2F1 mouse the MED by Hooker-Forbes bioassay of progesterone was 0.0005 μg; of 20α-hydroxyprogesterone, 0.0004 μg; of 20β-hydroxyprogesterone, 0.00006 μg; of 16α-hydroxyprogesterone, 2.0 μg. Progestin activity of mixtures of progesterone with 16α-hydroxyprogesterone, 20α-hydroxyprogesterone, and 20β-hydroxyprogesterone was measured by the same assay in CHI and B6D2F1 mice. Synergisms, partial antagonisms, and complete antagonisms were exhibited and were shown to depend on the components of the mixtures and their amounts and proportions.

Progesterone, 16a-hydroxy-progesterone, and maintenance of pregnancy in mice.

Summary In the Hooker-Forbes bio-assay in CHI mice, the minimal effective dose of 16a-hydroxy-progesterone was 0.006 μg. Subcutaneous pellets of this compound did not affect the normal duration of pregnancy or survival of fetuses in intact mice. In mice implanted with 2 progesterone pellets (about 18 mg) of pure progesterone on day 12 of pregnancy and ovariectomized on day 14, fetal survival was good. If pellets of 16a-hydroxy-progesterone were substituted, total abortion promptly occurred. If the pellets were a mixture of 16a-hydroxy-progesterone and progesterone, some fetuses survived, the survival rate diminishing as the proportion of 16a-hy-droxy-protesterone to a fixed amount (about 18 mg) of progesterone increased.

Inactivation of progesterone by fetal mouse tissues in vitro.

Summary Homogenates of whole fetal mouse of the 12th, 13th, and 14th days of pregnancy and of fetal mouse liver of the 15th and 16th days inactivate progesterone in vitro.