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Background: Locally produced androgens and estrogens are important in the hormonal regulation of follicular development. The present study aimed to further elucidate the mechanism through which androgens exert their ambivalent effects on aromatization., Methods: Non-cultured human granulosa-luteal cells (GC) were treated with different concentrations of androstenedione (A4), testosterone (T), 5alpha-androstane-3,17-dione (5alpha-A) and dihydrotestosterone (DHT). The effects on aromatase activity were evaluated in a tritiated water assay (incubation time 2 h) and the availability of aromatase active sites was measured in a radiotracer-binding assay using the non-steroidal competitive aromatase inhibitor [11C]-vorozole (incubation time 15 min)., Results: A4, T and 5alpha-A caused dose-dependent inhibition of both aromatase activity and [11C]-vorozole binding; IC50-values for both inhibition processes were calculated for these three steroids, revealing A4 as the most potent inhibitor and T and 5alpha-A as moderate inhibitors. At low concentrations (0.01 and 0.1 micro M), DHT stimulated aromatase activity but did not affect [11C]-vorozole binding. At the higher concentrations tested (1 and 10 micro M) DHT suppressed both processes thus weakly binding the aromatase active site., Conclusion: Because the incubation time in the tritiated water assay was short, the stimulation by DHT at low concentrations might therefore most likely include mechanisms other than new synthesis of aromatase protein such as allosteric action of DHT upon aromatase or liganded androgen receptor-aromatase interaction.

Background: Infertile women in Sweden are offered in vitro fertilization (IVF) within the frame of the social security system. The present investigation was undertaken to evaluate the prevalence of genital human papilloma virus (HPV) infection in relation to the results of cytologic screening and to the infertility in these women., Material and Methods: Two hundred and fourteen women, mean age 32 years (range 20-40), admitted to the Center for Reproduction at Uppsala University Hospital for investigation of infertility and IVF were studied. Human papilloma virus tests were performed by a sensitive polymerase chain reaction-based technique in cervical smears obtained at a medical examination or during oocyte retrieval. Cytologic screening results were obtained from medical records or at the time of investigation. The infertile women were compared with 197 healthy female controls., Results: Infertility resulted from female factors in 47% and male factors in 29% of the cases, and remained unexplained in 24%. Seven percent of the infertile women were HPV-positive compared with 9.1% of the controls. Only genital and oncogenic HPV types were identified. Human papilloma virus type 16 was most prevalent, and examination of the HPV 16 E6 gene showed that this prototype predominated over variants. No correlation was found between HPV infection and cause of infertility. Abnormal cytology was observed in 2.3% of the infertile women and 4.1% of the controls., Conclusions: Human papilloma virus infections might appear somewhat less frequently in infertile women admitted for IVF than in a control population. In both groups HPV infection was more common than cytologic abnormalities, possibly indicating that present HPV tests are more sensitive in detecting HPV infections than cytologic screening.

Infertility caused by ovarian failure is a characteristic feature in Turner's syndrome. Spontaneous pregnancies are seen in 2-5% of these women, and up to 30% have at least some pubertal development, indicating the presence of follicles in their ovaries in adolescence. It has not been clear at which age the follicles disappear. We analyzed the numbers and densities of follicles in ovarian cortical tissue from nine adolescent girls with Turner's syndrome who came to our clinics after having been informed about the study, with an aim to preserve ovarian tissue for possible infertility treatment later in life. A quarter to one whole ovary was laparoscopically removed for the procedure. Follicles were seen in the biopsy tissue in eight of nine subjects from whom ovarian tissue was laparoscopically obtained, the highest numbers being seen in the youngest girls and in those with mosaicism. In one 17-yr-old girl, no ovarian tissue was found. Follicle density was correlated with serum levels of FSH; individuals with the lowest FSH levels had the highest follicle density. One to 190 follicles were counted in the approximately 0.1-2.0 mm(3) of tissue analyzed, giving a density of 1.5-499 follicles/mm(3) of ovarian cortical tissue. Girls up to the age of 17 had primordial follicles in their ovaries. Three girls, two aged 15 yr and one aged 19, had only secondary follicles, with many being atretic. Our finding that adolescent girls with Turner's syndrome still have follicles in their ovarian cortical tissue raises the possibility of future fertility through cryopreservation of ovarian tissue. However, before such procedures can be recommended for clinical management, it is essential that future studies be performed to determine whether the oocytes retrieved from girls with Turner's syndrome have a normal chromosomal complement.

Background: To determine whether prolongation of embryo culture in vitro from day 2 to day 5 after ovum pick-up (OPU) and fertilization can improve the results of in vitro fertilization (IVF), and the morphology of the spare embryos on day 2 can predict the developmental capacity during prolonged culture. We also wanted to consider this as a strategy to avoid twin pregnancies if it could be possible to transfer only one blastocyst at a time in the future., Methods: A retrospective analysis with embryo transfer timed according to the weekday of OPU. Embryo transfer was performed on day 2 in 103 cases and on day 5 in 120 cases. Only one cycle per couple was included., Results: The pregnancy rates per embryo transfer on day 2 (27/103, 26%) and day 5 (36/120, 30%) were similar. There were significantly more miscarriages in the day 5 (50%) than in the day 2 group (22%, p = 0.02), but there was no significant difference in the baby take home rate (20% in day 2 group, 15% in day 5 group). The morphological appearance of the embryos on day 2 was poorly correlated to the developmental potential during prolonged culture in vitro. On day 5, transfer of one or two blastocysts resulted in a pregnancy rate that tended to be higher than that after transfer of morulae only., Conclusion: Prolongation of embryo culture from day 2 to day 5 did not improve the clinical outcome of the IVF treatment when measured as baby take home rate. Therefore, for the time being, this strategy does not increase our chances to move towards single embryo transfer.

We have studied the chromosomal content in 68 normally fertilised freeze-thawed human embryos of good morphology from 34 patients with an average maternal age of 32,6 years. Forty embryos showed post-thaw cellular division and twenty-eight post-thaw cleavage arrest. After spreading of the embryos on microscope slides, analysis of chromosomes X, Y, 15, 16, 17 and 18 was performed using two rounds of fluorescent in situ hybridisation (FISH). According to the results, the embryos were divided into four groups: (I) normal, all nuclei uniformly diploid, (II) diploid mosaics, normal diploid blastomeres in combination with abnormal blastomeres, (III) abnormal, all nuclei abnormal, (IV) chaotic, the chromosome constitution varies randomly from cell to cell. Approximately 25% of the embryos had normal number of the chromosomes tested, while the majority of the embryos were abnormal. Most of the abnormal embryos were diploid mosaics (57%). This was true for the embryos showing cleavage division as well as the embryos showing cleavage arrest. Our data show a slightly higher incidence of abnormal embryos compared to those obtained with FISH in non-cryopreserved embryos and confirm that the majority of preimplantation embryos fertilised in vitro contain abnormal blastomeres. The results, mechanisms, significance and implications are discussed.

An in vitro method for measuring aromatase cytochrome P450 enzyme (P450AROM) in human granulosa cells (GC) has been developed, based on binding of the 11C-labeled aromatase inhibitor vorozole. GC were obtained following superstimulation during in vitro fertilisation. The method revealed a binding affinity (Kd) of 0.4 nM and a maximum binding (Bmax) at 11 fmol/4000 cells which is equal to 1.6 million binding sites per cell. Linear Scatchard plots indicated a single type of binding site. P450AROM concentrations measured by [11C]vorozole binding correlated positively with aromatisation of [1beta-3H]androst-4-ene-3,17-dione measured as [3H]water release, and a positive association was also found with the ovarian in vivo response to follicle-stimulating hormone (FSH) stimulation expressed as 1000 times the ratio of the number of oocytes recovered from a patient and the total dose of recombinant FSH administered. Frozen cells could be used for P450AROM quantitation, provided the correct freezing procedure was used. Quantitation of P450AROM, based on binding of [11C]vorozole is an accurate and sensitive in vitro method, which might be extended to the measurement of aromatase expression by a noninvasive technique in the intact ovary in vivo using positron emission tomography.

Objective: To compare two gonadotropin-releasing hormone agonists for down-regulation prior to superovulation in in vitro fertilization/embryo transfer treatment., Methods: Infertility patients (n=181) were randomized to receive buserelin (1200 microg/day, n=90) or nafarelin (800 microg/day, n=91) intranasally starting in the luteal phase. Serum levels of LH, estradiol and progesterone were measured during the treatment. The cycles were compared with regard to number of oocytes, fertilization and implantation rates and achieved pregnancies., Results: Serum LH was lower after two weeks on buserelin: 1.8 (1.3-2.4) IU/L (median, with lower and upper quartile in parenthesis), than after nafarelin: 2.6 (1.8-4.0) IU/L, (p=0.0001). No other differences in serum hormone levels could be detected. More oocytes were recovered in the buserelin group: 13.0 (8.0-19.0) vs 11.0 (6.8-15.0), (p=0.046), but the fertilization rate was higher in the nafarelin group (49.9%, vs 45.1%, p=0.023). Implantation rate was higher in the nafarelin group (26.28% vs 15.5%, p=0.030), but there were an equal number of deliveries in both groups (20.9% vs 15.6% per started stimulation, p=0.420). In the subsequent frozen-thawed embryo transfer cycles the implantation rate was 21.1% (nafarelin group) and 10.6% (buserelin group, p=0.067), the pregnancy rate/ET was 31.7% and 17.0% (p=0.107) and the delivery rate was 22.0% and 10.6% (p=0.148), respectively., Conclusions: Differences exist in IVF-cycles down-regulated with buserelin or nafarelin which might affect embryo quality and treatment outcome.

Objective: To determine the effects of gonadotropin-induced ovarian stimulation on the plasma levels of endothelin-1 as well as on uterine blood flow and endometrial thickness., Design: Controlled cross-over clinical study., Setting: Academic research environment., Patient(s): Eighteen volunteer infertile women (31.4 +/- 2.5 years, mean +/- SE) participating in an IVF-ET program., Intervention(s): Transvaginal Doppler ultrasound was performed and blood samples were collected 4 days after the LH surge in a spontaneous cycle and 4 days after hCG administration in a subsequent gonadotropin-stimulated cycle., Main Outcome Measure(s): Plasma levels of E2, P, and endothelin-1; uterine artery pulsatility index; and endometrial thickness., Result(s): Stimulated cycles were associated with significantly higher E2 levels (101.0 +/- 10.2 versus 723.5 +/- 57.3 pg/mL [conversion Factor to SI unit, 3.671]; spontaneous versus stimulated), thicker endometrium (9.2 +/- 2.5 versus 11.4 +/- 2.9 mm), and lower endothelin-1 levels (2.5 +/- 0.1 versus 2.1 +/- 0.1 pg/mL [conversion factor to SI unit, 0.4]) and pulsatility index (3.22 +/- 0.12 versus 2.63 +/- 0.08) than spontaneous cycles. Endothelin-1 correlated negatively with E2 (r = -0.38), but not with P or pulsatility index. Differences in endothelin-1 and endometrial thickness between spontaneous and stimulated cycles correlated negatively (r = -0.56) with each other., Conclusion: Our results suggest an inhibitory role for E2 in the release of endothelin-1, which could be a factor in the regulation of uterine and endometrial blood flow.

Objective: To verify whether uterine artery impedance, measured as pulsatility index and resistance index is related to the outcome of in IVF-ET cycles., Design: Prospective study of infertile women participating in an IVF-ET program., Setting: University Hospital., Patients: Two hundred women (24 to 40 years of age), who had one to three good quality embryos transferred to the uterus after a standardized IVF cycle., Intervention: Transvaginal color Doppler and a blood sample on the day of ET., Main Outcome Measures: Uterine artery pulsatility index and resistance index, endometrial thickness, serum E2 and P concentrations, clinical pregnancy rate (PR)., Results: Pulsatility indices and resistance indices were lower in conception (2.45 +/- 0.54 and 0.85 +/- 0.04, respectively) than in nonconception cycles (2.66 +/- 0.39 and 0.87 +/- 0.04, respectively), although the overlap of the values is considerable. Overall PR was 35% per ET, and it decreased significantly when pulsatility index was > 3.0 (15%) and resistance index > 0.92 (13%), being lowest when pulsatility index was > 3.3 and resistance index > 0.95 (10%). Such a high impedance was detected in 9% of nonconception cycles., Conclusion: In IVF-ET cycles the uterus is likely to be unreceptive when uterine artery pulsatility index is > 3.3 and resistance index > 0.95 before ET, but this occurs only in 9% of the cycles.

Objective: To evaluate the effect of elective cryopreservation of all embryos in the prevention of severe ovarian hyperstimulation syndrome in women at increased risk, following superovulation for in vitro fertilisation., Design: Three hundred and ninety women undergoing superovulation for in vitro fertilisation between September 1991 and December 1992., Setting: University Infertility Clinic, Helsinki, Finland., Interventions: Twenty-three women were considered to have an increased risk of developing ovarian hyperstimulation syndrome. They were characterised by more than 20 retrieved oocytes and/or by serum oestradiol levels exceeding 10,000 pmol/l on the day of administration of human chorionic gonadotrophin. Instead of cancelling the cycle the oocytes were harvested and fertilised, and all good quality embryos were cryopreserved. The embryos were thawed and replaced during subsequent natural cycles., Main Outcome Measures: Occurrence of ovarian hyperstimulation syndrome and pregnancy rate., Results: One out of the 23 patients at increased risk developed a moderate degree ovarian hyperstimulation syndrome, while the others had only mild symptoms. Two of the remaining 367 women with no risk developed ovarian hyperstimulation syndrome, both during early pregnancy. Among the 23 patients at increased risk there have been 15 clinical pregnancies after transfer of two to three frozen-thawed embryos in natural cycles, with a 32.6% pregnancy rate., Conclusions: Withholding embryo replacement and elective cryopreservation of the embryos is effective in preventing severe ovarian hyperstimulation syndrome. After subsequent replacement in natural cycles the implantation rate per embryo is good (22.7%).

The in vitro binding affinities of toremifene (TOR), 4-hydroxy toremifene (4-OH-TOR) and several other metabolites for the rat uterine cytosolic estrogen receptor were compared with those of tamoxifen (TAM) and 4-hydroxy tamoxifen (4-OH-TAM). Only small differences were observed and the binding affinities of both 4-hydroxy metabolites were similar to that of estradiol (E2). Uterine uptake and subcellular distribution of [3H]TOR and [3H]TAM were then compared at 1, 8 and 72 h after administration to castrated rats. The uptake and retention of both antiestrogens were similar at all times. In each case the amount of nuclear bound radioactivity declined to low levels at 8 and 72 h but the ratios of 4-OH-TAM/TAM and 4-OH-TOR/TOR determined by HPLC analysis increased dramatically at 72 h. The level of radioactivity in both plasma and uterine cytosol at 72 h was significantly higher following [3H]TAM administration. However, most of the radioactivity appeared to be in a conjugated form since it was not extractable with solvent. Finally, the ability of prior administration of each antiestrogen (100 mg/kg) to block uterine [3H]estradiol uptake was examined at 3 and 7 days. It was found that uterine wet weights were higher than control one week after administration of both compounds. Prior administration of TOR increased nuclear uptake of [3H]E2 whereas TAM had no effect. The results of these experiments suggest that toremifene and tamoxifen have very similar in vitro and in vivo binding properties but differences in metabolism exist that may be important.

The serum pancreatic and catalytic phospholipase A2 level (PLA2) in human pregnancy is normal, and the increase of pancreatic enzyme before delivery is small. In patients with pruritus associated with obstetric hepatosis maternal serum had a slightly lower pancreatic PLA2 level if the cholic acid level was higher. Umbilical cord blood has twice as much pancreatic PLA2 as maternal blood. If the enzyme concentration was very high, pregnancies were postterm and the newborns had low Apgar scores. Amniotic fluid contains these enzymes, but there is no change in the enzymes during the course of pregnancy. The amount of pancreatic enzyme was not reflected in catalytic activity. A very high PLA2 activity was observed in 1 patient with suspected amniotic fluid embolism and in the meconium, but low in the first urine of neonates.

14C-Arachidonic acid (AA, 66 nmol) was injected into the pulmonary circulation of isolated perfused hamster lungs. The metabolites were analysed from the nonrecirculating perfusion effluent, which was extracted with ethyl acetate first at pH 7.4 (to extract unmetabolized AA, metabolites of lipoxygenase and HHT) and then at pH 3.5 for prostaglandins and thromboxanes. When indomethacin was infused into the pulmonary circulation, the metabolism of AA was decreased dose dependently. The amounts of all metabolites were decreased rather similarly by indomethacin. The present study indicates that indomethacin inhibits arachidonate metabolism via cyclo-oxygenase and lipoxygenase in hamster isolated lungs.

The ability of the lungs to release fatty acids from circulating triglycerides or lipoproteins for its own phospholipid synthesis may be one of the factors which limit the rate of surfactant formation. Therefore, the development of the lipolytic activity of lungs obtained from late fetal and neonatal rabbits has been studied and the results correlated to the phospholipid content of lungs of similar ages. Isolated lungs were perfused with a medium which contained cold and radioactive triglyceride, and the release of fatty acids into the perfusion medium was analyzed by both colorimetric and radiochemical methods. The phospholipids of the postmitochondrial supernatant fractions of the lungs were extracted and quantified by measuring inorganic phosphorus. Finally, the influence of maternal cigarette smoke exposure on the lipolytic activity of the lungs of their litters were studied. A high lipolytic activity in the lungs of 28-day-old fetuses was detected. The activity decreased towards birth, and was lowest on the first day after birth (about 20% of that observed in 28-day-old fetuses). However, it increased again during the first week after birth. Exposure of the mothers to cigarette smoke during the last 10 days before delivery did not affect the pulmonary lipolytic activity of the offspring. Although the lung phospholipid content increased 3.6-fold from 28 days of fetal life to 1 week after birth, it remained unchanged on the days when the lung lipolytic activity was lowest. We conclude that changes in lung lipolytic activity influence lung phospholipid synthesis, and consequently influence also surfactant formation in the lungs.

Aspirin (100 microM or 1 mM) or indomethacin (10 microM or 100 microM) was incubated with a microsomal preparation of hamster lungs in the presence of NADPH for 10 min. Then 14C-arachidonic acid (20 microM) was added and the incubation was continued for an additional 20 min. The metabolites were extracted with ethyl acetate first at pH 7.4 and then at pH 3.5 and analysed by thin layer chromatography. Both aspirin and indomethacin inhibited dose dependently the formation of all identified prostaglandins, including PGF2 alpha, 6-keto-PGF1 alpha, PGE2 and PGD2. The rate of formation of some unidentified metabolites extracted at pH 7.4 and 3.5 was, however, not changed by aspirin or indomethacin. We have earlier reported that in isolated perfused hamster lungs the formation of all arachidonate metabolites is inhibited by both aspirin and indomethacin. As the present study indicates that in the microsomes of hamster lungs all metabolic pathways of arachidonic acid are not inhibited by aspirin or indomethacin, it is possible that in isolated tissues and in vivo aspirin-like drugs have some other inhibitory effects on arachidonate metabolism than the inhibition of the cyclo-oxygenase enzyme.

Pregnant rabbits were treated with aspirin (100 mg/kg/day) for ten consecutive days during the last third of the pregnancy. The ability of isolated perfused fetal rabbit lungs to metabolize arachidonic acid (AA) was studied on the 31st day of the pregnancy. After the infusion of 14C-AA (100 nmol) into the pulmonary circulation about 10% of the radioactivity was found in the nonrecirculating perfusion effluent and about 80% was incorporated into the lung lipids. Aspirin pretreatment of the rabbits inhibited the formation of AA metabolites in the lungs of their fetuses. The inhibition was clear when the metabolites of AA were extracted from the perfusion effluent at pH 7.4 (mainly lipoxygenase products) but a slight inhibition was also seen in the amounts of some metabolites extracted at pH 4.5 (cyclo-oxygenase products). When aspirin (1 mM) was infused simultaneously with AA into the pulmonary circulation the inhibition of AA metabolism was nearly complete. Aspirin pretreatment of the pregnant rabbits caused a slight increase in the amount of 14C-AA incorporated into some of the phospholipid and neutral lipid fractions of the perfused fetal lungs. Aspirin pretreatment clearly inhibited the TXB2 formation during clotting in the blood of maternal rabbits but not significantly in the blood of their fetuses.

The developmental pattern of fetal and neonatal rabbit lungs to generate an antiaggregatory compound from arachidonic acid (AA) was studied in isolated rabbit lungs, which were perfused with Krebs bicarbonate buffer. The antiaggregatory effect of the nonrecirculating perfusion effluent was tested by adding a small portion of the effluent to human platelet rich plasma (PRP) in a Born-type aggregometer before the aggregation was induced by ADP. The production of an antiaggregatory compound was minimal, when exogenous AA was not infused into the pulmonary circulation. When arachidonate (40 nmol/min) was infused into the pulmonary circulation of rabbits which were 1 day or 1 week old, the perfusion effluent significantly inhibited the ADP induced aggregation of PRP. Perfused lungs from fetal rabbits (gestation age 28-31 days) formed also an antiaggregatory compound from AA, but the antiaggregatory effect was not as great as 1 day after birth. It seems that neonatal rabbit lungs metabolize AA more to an antiaggregatory compound than late fetal lungs. The fact that the AA induced production of an antiaggregatory compound is inhibited by simultaneous infusion of indomethacin favours the hypothesis that this antiaggregatory compound could be PGI2.

The effects of nicotine and carbon monoxide on the production of PGI2 by rat arterial rings were studied. For PGI2 analysis, we used a bioassay based on platelet-rich plasma aggregation with ADP. Neither nicotine in the incubate nor pretreatment with carbon monoxide decreased PGI2-production as detectable in this bioassay system. Also, neither had a direct effect on the ADP-induced aggregability of human platelet-rich plasma. Consequently, these agents do not seem to be responsible for the temporary increase in platelet aggregability after cigarette smoking.

The activity of aryl hydrocarbon hydroxylase (substrate: benzo(a)pyrene) was increased in the tracheas of rats exposed to cigarette smoke for 1 h daily for either 1 or 10 days. However the degree of increase in activity was lower in the trachea than in the lung. After a single exposure, activity in the trachea was at its highest level 12 h following exposure (3.2-fold compared to the control), but had returned to the control level within 24 h. Also, the amounts of covalently bound metabolites of benzo(a)pyrene were increased (2-fold) in nucleic acid and protein fractions of the trachea, when the rats were killed 12 h after a single cirgarette smoke exposure. No significant changes in activity of epoxide hydratase (substrate: styrene oxide) could be detected in the trachea. After repeated exposures the activity of UDP-glucuronosyltransferase (substrate: methylumbelliferone) was increased (1.7-fold) in the trachea.

We have provided a brief historical review of developments in our understanding of the endocrine mechanisms underlying the expression of androgen action in women. An alternative to the free hormone concept is considered which proposes that, at least in some target cells, androgens bound to SHBG are the biologically relevant molecules. In nearly every instance, the changes in blood levels of SHBG that have been observed are consistent with this idea. At present there are only bits of direct evidence to support the hypothetical mechanism proposed. As already mentioned, control of androgen action at the level of cellular uptake would provide obvious advantages as well as a potential mechanism to explain the antagonism between androgens and oestrogens which is still a mystery. It is important to note that the proposed mechanism is not obligatory for androgen or other steroid hormone action. Synthetic steroids which do not bind to SHBG or CBG clearly can gain access to target cells by simple diffusion and bind to intracellular receptors. Compounds such as methyltestosterone and dexamethasone are metabolized much more slowly than their natural counterparts and therefore are cleared slowly from the circulation. It is possible that the well-known difficulties in selecting appropriate therapeutic regimens with such compounds is related to the fact that they bypass an important regulatory step in steroid hormone action-modulated entry into target cells. Hopefully, the recent development of powerful new tools of molecular endocrinology will hasten the answer to the question: What is the active androgen in blood?

The inactivation of prostaglandin E2(PGE2) and 5-hydroxytryptamine (5-HT) was studied in isolated perfused lungs from fetal and neonatal rabbits. PGE2 inactivation was considerable already at the 28th day of fetal life, as only 11% of injected substrate survived passage through the pulmonary circulation. However, the inactivation increased significantly during the last 3 prenatal days (4% survival) and remained at this level when analyzed one week postnatally. In contrast to PGE2-metabolism, 5-HT inactivation was relatively stable during the studied fetal period (47-49% inactivation), but was decreased significantly on the 7th day postnatally when compared to newborn litters. The results indicate that pulmonary prostaglandin and amine metabolism reach maturity at different times during the perinatal period.

The inactivation of prostaglandin E2 (PGE2) was studied in isolated perfused lungs of fetal and neonatal rabbits. 200 nmol of 14C-PGE2 was infused into the pulmonary circulation and the metabolites of PGE2 were analysed from the nonrecirculating perfusion effluent. The amount of the main metabolite, 13,14-dihydro-15-keto-PGE2, increased significantly between the 28th and 30th day of fetal life, remained relatively constant at the time of birth and increased again between 1st and 7th postnatal day. In contrast, the amount of 15-keto-PGE2 remained relatively stable during the studied period. The activity of NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-OH-PGDH) was determined from the 100.000 g supernatant fraction of fetal, neonatal and maternal rabbit lungs using 14C-PGE2 (20 microM) as the substrate. In the lungs of late fetal rabbits the activity of 15-OH-PGDH was significantly higher compared to the early postnatal period. Maternal rabbit lungs possessed, however, very high activities compared to the studied perinatal lungs. The results show, that the activity of the pulmonary 15-OH-PGDH is high already during the late fetal period. The inactivation of PGE2 in isolated perfused lungs seems, however, to increase during the last prenatal days. Thus it seems possible that the uptake mechanism could be the rate limiting step in the metabolism of PGE2 in rabbit lungs during the perinatal period.

The developmental pattern of fetal and neonatal rabbit lungs to metabolize arachidonic acid (AA) to different cyclo-oxygenase products was studied in isolated rabbit lungs, which were perfused with Krebs bicarbonate buffer. 14C-AA (66 nmol) was injected into the pulmonary circulation and the nonrecirculating perfusion effluent was collected for four minutes. About ten per cent of the injected radioactivity was found in the 0-4 min perfusion effluent. The metabolites of AA in the effluent were analyzed by thin layer chromatography. The major metabolites of AA were PGE2 and its 15-keto-derivates, but also PGF2 alpha and its 15-keto-derivates, TXB2 and 6-keto-PGF1 alpha were found in the effluent. The most drastic developmental change was the increase in the amount of 15-keto-metabolites of PGE2 from late fetal period to the lungs of one day old rabbits (1.8 fold increase between birth and first postnatal day). Smaller changes were detected in the amounts of other cyclo-oxygenase products.

We investigated estrogen (estrone and estradiol) levels in serum and in nipple aspirates of breast fluid in relation to reproductive and menopausal characteristics in 104 normal women. In general, breast fluid and serum estrogen levels were not correlated and breast fluid estrogen levels were approximately 5 to 45 times higher than serum levels. Serum estrogen levels were lower in post-menopausal than in pre-menopausal women. In contrast, breast fluid estrogen levels were approximately the same in pre- and post-menopausal women. Breast fluid estrogen mean levels were lower in pre-menopausal parous women than in nulligravidous or nulliparous women whereas serum estrogen levels did not differ in these 3 groups. Breast fluid estrogen levels were positively correlated with months since last birth or since last breast-feeding. Estrogen levels were low in nipple aspirates of breast milk but gradually increased in breast fluid of non-lactating women over a period of several years after cessation of lactation. Serum estrogen levels did not increase with months since last breast-feeding. We were unable to evaluate the post-partum effect of pregnancy without lactation due to the small numbers of these subjects. The high concentrations of estrogen in breast fluid and the absence of a relationship to serum estrogen levels may explain why prior serum studies have failed to link variations in serum estrogens with breast cancer risk. The prolonged low levels of breast fluid estrogens following full-term birth and lactation may, in part, provide a mechanism by which parity reduces breast cancer risk.