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The availability of norethindrone (NET) in serum was studied in 8 women after daily administration of a combination oral contraceptive pill (MinovlarR) containing 1 mg norethindrone acetate (NETA) and 50 μg ethinyl estradiol (EE2) from day 5 to day 25 of the menstrual cycle. The pill was taken daily at 9.30 a.m. after a light breakfast and blood samples were collected at 3 hr on alternate days and at 24 hr on other days after ingestion of the pill. On day 12 or day 15 of the first treatment cycle, serial blood samples were also collected at 1/2, 1, 2, 4, 6, 8 and 24 hr after taking the pill. Serum NET levels were estimated by the radioimmuno-assay (RIA) technique. The plot of serum NET concentration versus time (0 — 24 hr) profile showed a rapid absorption of steroid and a peak NET concentration (18.3±4.8 ng/ml) reached at 2 hr after ingestion of the pill. By linear regression analysis of data (y = 0.27 + 0.12x; r=0.95), it was observed that the serum NET level was initially about 1 ng/ml. Thereafter, it increased by 0.12 ng/ml per day up to 3.5 ng/ml by the end of 21 days' treatment with oral pills. The serum NET concentration decay slope fitted a two-compartment open model with an initial rapid decay (half-life of 1.2±0.1 hr) followed by a slower β-phase with a half-life of 8.5±1.5 hr. The study revealed that there was an accumulation of norethindrone in plasma during the treatment period and this suggests the possibility of exploring a reduction in the dose of this preparation so as to achieve the optimum NET concentration for contraception, and thereby avoiding unwanted steroid accumulation in the plasma of women.

A study of the metabolism of oestradiol in the human endometrium and myometrium of the proliferative and secretory phases of the cycle showed that the conversion of oestradiol to oestrone by endometrium in the proliferative phase was higher than that in the secretory phase. The decreased metabolic activity of the secretory phase endometrium was attributed to the influence of progesterone on the endometrium. The metabolic conversion of oestradiol to oestrone was enhanced when pyridine nucleotides were added to the system. The conversion of oestradiol to oestrone was maximum in the cytoplasmic and nuclear fractions of the endometrium. Furthermore, the conversion of oestradiol was low in all the subcellular fractions of the myometrium as compared with the endometrial subcellular fractions. The presence of co-factors increased the metabolic conversion of oestradiol to oestrone in the subcellular fractions of the endometrium. The presence of 17β-hydroxysteroid oxidoreductase was indicated in all the subcellular fractions. A correlation was found between the amount of oestradiol and oestrone bound to the receptors in the uterus and the rate of metabolism of oestradiol in the uterus. The physiological significance of metabolism of oestradiol and the hormone action are discussed.

Studies on the metabolism of progesterone in rabbit plasma and tissues during constant infusion of [3H]progesterone revealed a gradual increase in the concentration of progesterone in plasma until a state of equilibrium was attained about 2 h after the start of infusion. The metabolic clearance rate of progesterone was 0·116 l/min and the turn-over time was 0·006 min/ml plasma. Under conditions of equilibrium, the concentration of radioactivity as well as that of labelled progesterone was higher in the tissues than in plasma. On a unit–weight basis, myometrium localized 6·6 nCi, Fallopian tube 5·5 nCi and vagina 6·1 nCi [3H]progesterone/g tissue. A higher concentration of progesterone, 16·5 nCi, was localized in the mammary gland tissue. Skin localized only 0·9 nCi progesterone and the lowest amount (0·34 nCi/ml) was found in plasma.The metabolism of progesterone in tissues differed from that in plasma. In plasma only 5·6% of the infused steroid was recovered as unconverted progesterone and the major amount was metabolized to polar compounds with smaller amounts of 5α-pregnane-3,20-dione, 5α-pregnan-3β-ol-20-one and 20α-hydroxypregn-4-en-3-one. In the myometrium and Fallopian tubes the major metabolites were 5α-pregnan-3β-ol-20-one and 5α-pregnane-3,20-dione respectively. In the vagina, like the myometrium, 5α-pregnan-3β-ol,20-one was the major metabolite. 20α-Hydroxypregn-4-en-3-one was the major identified metabolite of mammary gland tissue.

The in vivoand in vitrobinding of 3H-oestradiol-17β to cytoplasmic and nuclear fractions of the human endometrium and myometrium was demonstrated by different techniques. Sucrose density gradient ultracentrifugation of the endometrial cytoplasm showed that oestradiol binds with two specific proteins sedimenting at 8.5 S and 5.1 S. Myometrial cytoplasmic oestrogen binding protein (OeBP) had a sedimentation coefficient of 5.1 S. Nuclear OeBP in the endometrium and myometrium had the same sedimentation value of 4.2 S. The endometrial cytoplasmic OeBP separated by gel chromatography showed association with both oestradiol and oestrone in the ratio of 2:1. The OeBP in nuclear fraction of the endometrium and myometrium showed binding with oestradiol and oestrone in the ratio of 2.5:1 and 2:1 respectively. The association of oestrone along with oestradiol with receptors of the endometrial and myometrial nuclear and cytoplasmic fractions suggests that oestrone may play a significant role in the overall action of oestrogens in the human uterus. Studies on ligand specificity of the OeBPs showed that oestrone which is a comparatively weaker oestrogen, competitively displaced bound 3H-oestradiol, more or less in a similar way as a highly potent oestrogen diethylstilboestrol (DOeS). Chlormadinone acetate (CAP), among the progestational steroids tested, maximally displaced bound oestradiol. The significance of these findings in the mechanism of action of oestradiol in the human uterus is discussed.

The human endometrium and the myometrium have the capacity to convert [6,7-3H]norethynodrel to norethindrone, 17α-ethynyl-3α,17β-dihydroxy-5-(10)-oestrene and two other unidentified metabolites. Under in vitroconditions, 80–90 % of 3H-norethynodrel was converted to its metabolites within 90 min. The metabolites formed were the same for both the endometrium and the myometrium. The amount of norethynodrel converted to its metabolites was more in the proliferative phase than in the secretory phase. Among the subcellular fractions of the myometrium, mitochondrial and microsomal fractions metabolised norethynodrel to norethindrone and two polar metabolites with low chromatographic mobility. In the myometrial 105 000 × gsupernatant fraction, 17α-ethynyl-3α,17β-dihydroxy-5(10)-oestrene was formed in addition to norethindrone and the polar metabolites. The significance of the formation of norethindrone – a potent oral progestin as a product of the metabolism of norethynodrel and its possible action at the uterine level in the control of fertility is discussed.

After an iv injection of [14,15-3H]d,l-norgestrel into 7 women, its disappearance from the plasma and its distribution in the reproductive organs has been investigated. It was found that initially norgestrel disappeared rapidly from the plasma with a half-life of 38.8 min followed by a slower disappearance with a half-life of 45.18 h. The disappearance curve has been analysed on the basis of a biexponential curve representing a two compartmental model. The low metabolic clearance rate of 458.5 1/24 h indicated a more prolonged persistance of norgestrel in the body.Uptake of norgestrel and its metabolites was very high in the endometrium, myometrium, cervix, Fallopian tube, ovary and body fat. Compared to the myometrium. more norgestrel as such was concentrated in the endometrium at 30 min and 12 h after injection of [14,15-3H]d,l-norgestrel. The myometrium on the other hand contained higher amounts of norgestrel at 5 min. The significance and the possible role of localization of norgestrel at multiple sites in the reproductive tract and its contraceptive action are discussed.

The metabolic clearance rate (MCR) of norethindrone acetate1(NETA) and norethindrone (NET) levels in plasma were studied after an iv injection of [3H]NETA in three women before and at 1 week, 1, 2 and 6 months following the insertion of a single silastic subdermal implant releasing microquantities of NETA. No significant change in the MCR of NETA was observed at 1 week (459 ± 72 1/day), 1 month (489 ± 113 1/day) and 2 months (522 ± 144 1/day) compared with that of control (525 ± 108 1/day). However, MCR of NETA showed significant increase in women exposed to continuous presence of NETA for a period of 6 months (608 ± 121 1/day; P< 0.025). NETA was rapidly and extensively metabolized into NET. At 1 week, 1, 2 and 6 months of study, NET was observed to be present in higher amounts compared with NETA. The production rate (PR) of progesterone decreased significantly at 2 and 6 months of NETA implant insertion compared with the PR before the insertion of implant.

Summary.A 1·5 cm long copper wire caused complete inhibition of fertility in male rats when placed properly in the vasal lumen. The contraceptive effectiveness of the device was directly proportional to the surface area of the device and was non-obstructive. The release rate of copper in vivofrom a 1 ·5 cm long wire was 11·6 μg/day during the first month and 6·8 μg/day over the first 3 months. The contraceptive action of the wire starts about 20 days after insertion. Fertility was regained in 67% of the rats by 90 days after removal of the device. Similar devices of stainless steel and silver did not affect fertility.

Summary.Copper wire was inserted into the vas deferens and its effect on the reproductive system and fertility performance of rats was investigated. The copper wire was 100% effective as a contraceptive for up to 4 months if placed correctly, and resulted in decapitation of most of the spermatozoa. No differences between the rats with an intravasal copper wire and the sham-operated controls were found for the weights of the gonads and accessory sex glands or for protein, RNA, DNA and fructose concentrations. The intravasal copper device appears to be promising for the development of a long-term method for male contraception.

Under in vitroconditions, the human endometrium and myometrium metabolized norgestrel to 13β-ethyl,17α-ethynyl-5β-oestrane,3α,17β-diol; 13β-ethyl,17α-ethynyl-5β-oestrane,3β,17β-diol and to some unidentified polar compounds, which suggests that the enzyme 3-ketosteroid reductase is present in these tissues. There was no qualitative difference in the conversion of norgestrel to its metabolites by the endometrium and myometrium, though some quantitative differences were observed i.e. more norgestrel was metabolized by the proliferative as compared with the secretory endometrium and myometrium. Furthermore, the conversion of norgestrel to its metabolites was higher in the endometrium as compared with the myometrium. Among the subcellular fractions of the endometrium and myometrium, the cytosol fraction showed the highest conversion of norgestrel. The main metabolite formed in the endometrium, myometrium and in their subcellular fractions was 3α-hydroxy-5βH-tetrahydronorgestrel. The implications of the formation of metabolites of norgestrel with very low biological activity as a factor involved in the regulation of the action of norgestrel in the endometrium are discussed.

The metabolism of [3H]progesterone in the rabbit endometrium and myometrium was studied in vitro. The major metabolities identified were 5alpha-pregnane-3,20-dione, 20alpha-hydroxypregn-4-en-3-one, 3beta-hydroxy-5alpha-preganan-20-one and 5alpha-pregnane-3beta,20alpha-diol. Other minor metabolites tentatively identified were 3alpha-hydroxy-5beta-pregnan-20-one,20alpha-hydroxy-5beta-pregnan-3-one and 5beta-pregnane-3alpha,20alpha-diol. The ability of the endometrium to metabolize progesterone on a unit weight bais was about 2.7 times that of the myometrium. The metabolism of [3H]progesterone in the rabbit uterus under the influnce of oestradiol-17beta and progesterone was studied. The ability of the oestradiol-treated rabbit uterus to metabolize progesterone was increased to 3.47 times that of the overiectomized control uterus, whereas the oestradiol-progesterone-treated rabbit uterus metabolized only 1.86 times that of the control. Study of the metabolism of progesterone with uterine subcellular preparations revealed that the 5alpha-reductase enzyme was present mainly in the nuclear fraction; 20alpha-hydroxysteroid dehydrogenase was found in the cytosol fraction and 3beta-hydroxysteroid dehydrogenase in the particulate fraction of the uterus. The metabolic pathways of progesterone in the rabbit uterine tissue are discussed.

This paper deals with some aspects of uterine metabolism in the presence of an intrauterine contraceptive device (IUD) in the rat. The weight and protein content of the IUD-bearing horn, compared with the control horn, were increased in ovariectomized rats, in ovariectomized hormone-treated rats, and in cycling and pregnant animals. Acid and alkaline phosphatase and β-glucuronidase activities were higher in the IUD-containing horn than in the control horn, whereas the activity of lactic dehydrogenase was invariably lower in the IUD-bearing horn. The present finding of alterations in enzyme activities in the presence of an IUD in the rat uterus leads to the conclusion that an IUD changes the metabolism of the rat uterus. The increase in the activity of estrogen-stimulated enzymes in the presence of an IUD further supports the hypothesis that an IUD may be producing an estrogen-like effect.

This report deals with a comparative study of the uptake of radioactivity in the genital, neural and other tissues of intact male, castrate male and female rats after constant infusion of radiochemically pure 1,2-3H-testosterone. Castration has been found to have a marked effect in enhancing the uptake of radioactivity in the different tissues particularly liver and kidney which have a metabolic and excretory role.Prostate and seminal vesicles, on the other hand, did not show any difference in uptake in intact and castrate rats. The uptake of testosterone and its metabolites in the prostate of intact animals was 3.46 × 10−9m. In experiments on subcellular localization of radioactivity after constant infusion of 1,2-3H-testosterone, it was found that prostate and seminal vesicle had heavy localisation in the nuclear and 105 000 × g soluble fraction while the major localisation of radioactivity in the case of nontarget tissues like liver, intestine, muscle etc. was in the soluble fraction. Castration caused a higher uptake of radioactivity in the anterior pituitary gland, anterior and middle hypothalamus also, which could be explained on the basis of the negative feedback of the hormone. An interesting feature of the uptake of testosterone and its metabolites in the female rat was the high uptake in the anterior pituitary gland, and the various parts of the hypothalamus. These findings are discussed in light of information available on the action and feedback of sex hormones.

After an iv injection of [6,7-3H] norethynodrel to six women, the disappearance of radioactivity in plasma and the uptake in endometrium, myometrium and cervix at different times have been studied. The plasma disappearance curve due to norethynodrel and its metabolites showed an initial rapid disappearance with an average half-life of 76 min and a subsequent slower disappearance with a mean half-life of 45 h. The average volumes of distribution V1 and V̄ are about 17 and 119 litres respectively. The disappearance curve has been analysed on the basis of a biexponential curve representing a model consisting of two compartments. The second average half-life of 45 h is much longer than that of other hormones studied and it also explains the effectiveness of norethynodrel for 24 h or longer. Disappearance of radioactivity in the erythrocytes followed a similar pattern of disappearance of radioactivity in plasma, however, the levels were lower.The molar concentration of radioactivity was of the order of 14.5 × 10−9m in the endometrium, 7.1 × 10−9m in the myometrium and with the progress of time a higher uptake in the endometrium compared with the myometrium was found. Sub-cellular distribution showed 60–70% in the 105 000 g supernatant and 30% in the nuclear fraction of the endometrium. The significance of these results on the transport and action of norethynodrel is discussed.

The concentration of proteins, RNA and DNA, incorporation of carbon-14 amino acids into proteins and the labelling of RNA in 10 placentae each from normal and toxaemic pregnancies have been investigated. The protein content either on a wet tissue basis or on a dry tissue basis was lower in the toxaemic placenta. In this group of placentae, the concentration of RNA and DNA was also lower as compared with the normal. While there was no change in the RNA/Protein ratio in the two groups of placentae, the DNA/Protein ratio was significantly lower in toxaemic placentae. When the various subcellular fractions were compared, the concentration of protein was lower in the nuclear, mitochondrial, microsomal and pH 5 enzyme precipitate fractions of toxaemic placentae.The incorporation of carbon-14 amino acids into proteins and the labelling of RNA was lower in the various subcellular fractions of toxaemic placentae. The time course of the incorporation of carbon-14 amino acids into proteins and the labelling of RNA in cell-free system increased with time in both groups of placentae, however, these were lower in toxaemic placentae as compared with the normal at the various time intervals studied.From the data presented, it may be concluded that toxaemia exerts some deleterious effect on the biosynthesis of proteins in the placenta. It is suggested that damage to protein synthesis may be the cause of the altered biosynthetic and metabolic activities reported in the placentae during toxaemia.

The validity of the calculation of secretion rates from the specific activity of a urinary metabolite after the injection of the radioactive hormone (secretion rate equals radioactivity injected divided by the specific activity of a urinary metabolite ) has been critically examined. Although in previous applications of the method the expression has been assumed to be valid on an intuitive basis, it is concluded that this is not justified unless after continuous infusion the specific activity of the hormone is constant throughout the body. In the case of a single injection, where W has been termed the single injection factor, and must be equal to one for the method to be valid. If the transport and metabolism of the hormone can be described in terms of an outer and inner pool, it has been shown that the single injection factor is nearly equal to one unless the metabolite which is analyzed is formed mostly in one pool but the overall metabolism largely occurs in the other space.Other assumptions and sources of error in the method are discussed. It is concluded that a comparison of the specific activities of various metabolites is the most generally applicable experimental test of the validity of the method. On this basis, applications of the method to obtain the secretion rates of aldosterone and cortisol seem to be justified.

Reconsideration of the question of the validity of the calculations of the secretion rates from the specificity activity of a urinary metabolite after the single injection of a radioactive hormone has led us to conclude that the basic equations used in a previous theoretical treatment are not generally applicable to the nonisotopic steady state if the radioactive steroid and hormone are introduced into the same compartment. If this is so, in a two compartmental model with metabolism occurring in both pools, it is now shown that the calculation (S = R — τ) is rigorously valid if certain precautions are taken. This is in contrast to the previous treatment which concluded (in certain special circumstances) that the calculation might not be correct.However, if the hormone is secreted in both compartments and the radioactive steroid is injected into only one, then the calculation (S = R — τ) may not be correct in certain circumstances as was previously concluded (Laumas et al.1961).

This paper reports studies on the incorporation of [U-14C]glucose into lipid, RNA and proteins of the rat uterus in the presence of an IUD after treatment with oestrogen and progesterone and on Day 5 of pregnancy at the time of implantation. The results show that there is an increase in the incorporation of [U-14C]glucose into lipid, RNA and proteins in the IUD horn compared with that of the control horn of ovariectomized and oestrogen-treated animals. The increase in weight of the IUD horn compared with the control horn can be interpreted as due to an increased oestrogen-like response by the uterus in the presence of an IUD. This response may be caused by oestrogens, histamines or other amines.A significant decrease in the incorporation of [U-14C]glucose into lipid, RNA and proteins of the IUD horn compared with the control horn was found on treatment of the animals with oestrogen+progesterone and progesterone alone for 6 hr. Treatment of the animals for 9 days with oestrogen+progesterone also significantly depressed the rate of protein synthesis in the IUD horn compared with the control horn. On Day 5 of pregnancy at the time of implantation, there was a statistically significant decrease in the incorporation of [U-14C]glucose into lipid, RNA and proteins of the IUD horn compared with the control horn. These experiments indicated an increased sensitivity of the uterus to progesterone in the presence of an IUD.The uterus shows an increased oestrogen-like response in the presence of an IUD. The increased sensitivity of the uterus to progesterone at the time of implantation produces asynchronous changes in the uterus and results in an anti-implantation effect of the IUD. The mode of action of an IUD in the light of these observations is discussed.

The effect of long-term oral administration of norethynodrel and 17α-ethynyl oestradiol-3-methyl ether (mestranol, EO3Me) on biochemical changes in the uterus, ovary and adrenal of rabbits has been studied. It was found that the administration of norethynodrel significantly increased the incorporation of [U-14C]glucose into lipid, RNA and protein of the rabbit uterus. In this respect, the effect of norethynodrel resembled that of an oestrogenic compound besides its known progestational action. EO3Me increased glucose metabolism and its incorporation into lipid and RNA in the uterus. Norethynodrel also increased lipid and protein synthesis in the ovary, but EO3Me enhanced only lipid synthesis in the ovary. Glucose metabolism was markedly depressed in the adrenal gland after the administration of norethynodrel. The mode of action of norethynodrel has been discussed in relation to the disturbance in the biochemical changes it produced in the uterus and the ovary.

Little information is available on the uptake of progesterone by various tissues of the rat. In the present investigation ovariectomized adult female rats were primed with oestradiol and the disappearance of [1,2-3H]progesterone was studied after a single injection. Tissue and blood samples were removed after varying intervals of time and radio activity was determined with a liquid scintillation counter (Packard, Model 3324) after dissolving the tissues in hyamine. Tritiated toluene was used as an internal standard for quenching corrections. The results are presented in Fig. 1.The data indicate that progesterone (and its metabolites) is rapidly taken up by the brain and pituitary. The portion of brain taken for determination of radioactivity included a part of the hypothalamus and adjoining cortical areas. Within 2 min. of the injection, maximum radioactivity, which is of the order of 7·2 × 10−9and 5·7 × 10−9moles/kg., respectively, was