Short term changes in melatonin and cortisol serum levels after a single administration of estrogen to menopausal women.

OBJECTIVES: It has been well-documented that serum melatonin levels are insensitive to estrous or menstrual ovarian steroid variations in the female rat or the human. However, a negative coupling has been already demonstrated between the nocturnal serum melatonin peak and serum E2 concentration during the late premenopausal period in the woman. The objection of the present study was designed to determine if diurnal serum melatonin values can be also lowered by a single administration of estrogen. METHODS: We performed a detailed analysis of variations of serum estradiol, LH, FSH, melatonin and cortisol after one single I.M. injection of 2 mg of a conjugated estrogen, delestrogen (estradiol valerate) in 0.1 ml of oil. A 15 ml blood collection was done at 8:00 a.m. before the injection, and at 8:30 a.m., 9:00 a.m., 10:00 a.m., 12:00 noon, and 4:00 p.m. 17beta-estradiol, LH and FSH were determined by microparticle enzyme immunoassays kits. Melatonin determination was made using a RIA kit and cortisol was assayed by a RIA method. RESULTS: A significant rise in serum 17beta-estradiol was already seen by one hour after the injection of estradiol valerate. Then, an almost linear increase was observed up to at last eight hours after the injection of estradiol valerate. A significant decrease in serum LH was not seen before four hours after the injection of estradiol valerate. Overall, there was a trend toward a decline in serum melatonin and cortisol concentration. The decreasing trend of cortisol serum level was tested as significant over time (p< 0.001). However, the decrease in serum concentration did not reach a significant level for melatonin. CONCLUSION: Overall, these results show that after menopause an acute administration of estrogen during the early diurnal period of the day leads to a significant rapid decrease in cortisol serum values, but to only a partial non significant decrease in melatonin serum values.

Substance P plasma concentration during the LH preovulatory surge of the menstrual cycle in the human.

OBJECTIVES: In order to determine the exact pattern of plasma Substance P (SP) concentration during the LH preovulatory surge and the functional correlates which could exist between plasma SP, LH, 17 beta-estradiol (E2) and Progesterone, we performed a detailed analysis of changes in plasma SP concentration, during the critical phases of the LH preovulatory surge in the Human. METHODS: The experimental study was performed in 21 women between the ages of 26 and 35 years. For each subject, blood samples were taken every 15 min, between 07:00 a.m. and 09:00 a.m. for 3 consecutive days when E2 plasma values reached at last 125 pg/ml. Then, each subject, according to the mean LH value of each day, was classified into one of the following groups: 1) the day before the day of the ascending phase, 2) the day of the ascending phase, 3) The day of the LH surge, 4) the day of the descending phase, 5) the day after the day of the descending phase. RESULTS: Mean SP plasma values for the day of the LH peak, the day of the descending phase and the day after the day of the descending phase were all significantly higher than the values of the day of the ascending phase. Overall, there was an almost linear increase for plasma SP values between the day before the day of the ascending phase and the day after the day of the descending phase Also,this linear increase in plasma SP concentration exhibited a positive correlation (p = 0.016) with plasma progesterone concentrations which also started to increase on the day of the ascending phase of the LH surge. CONCLUSIONS: Taken together with previous results which have shown that the administration of a SP antagonist reduces both the amplitude and the duration of the preovulatory LH surge in the monkey, the increase in plasma SP concentrations, possibly driven by the rise in serum progesterone concentration, which take place at the time of the preovulatory LH surge, is certainly an important element of the Hypothalamo-Pituitary-Gonadal interactive network necessary for the full development of the preovulatory LH surge in the Human.

ACTH-cortisol activity during the 17beta-estradiol and LH preovulatory surges of the menstrual cycle.

OBJECTIVES: A strong positive coupling has been already documented between the adrenocortical axis and the gonadal axis at the time of the initiation of the preovulatory LH surge of the menstrual cycle in the human. The LH preovulatory surge starts in the morning at the time of the acrophase (maximal plasma cortisol values) of the cortisol circadian rhythm. Also, it was shown that morning maximal plasma cortisol values were higher during the follicular phase than during the luteal phase. The objective of the present study was designed to determine the exact day of the fall of morning maximal plasma cortisol values and the functional correlates which could exist between plasma 17beta-Estradiol, LH, ACTH and Cortisol at the time of the preovulatory LH surge. METHODS: We performed a detailed analysis of variations of plasma ACTH and cortisol concentrations during the various phases of the LH surge: 1) the day before the ascending phase, 2) the day of the ascending phase, 3) the day of the LH peak, 4) the day of the descending phase, 5) the day after the descending phase. 17beta-Estradiol, LH and FSH were determined by microparticle enzyme immunoassays kits and Progesterone determination was made using a radioimmunoassay kit. ACTH determination was made using a RIA kit and Cortisol was assayed by a RIA method. RESULTS: Plasma ACTH concentrations were at their highest the day before the day of the ascending phase of the LH surge and significantly higher than the day of the descending phase and the day after the day of the descending phase (p < 0.02). Plasma cortisol concentrations were at their highest, with almost similar values, the day before the day of the ascending phase, the day of the ascending phase and the day of the LH peak; then, plasma cortisol concentrations were significantly lower than those of the preceding days, the day of the descending phase (p = 0.0001) and the day after the day of the descending phase (p = 0.02), when plasma 17beta-Estradiol starts to decrease. CONCLUSION: Overall, these results suggest that the positive ACTH-Cortisol-Estrogen dependency, well documented in the female rat, is also operating at midcycle during the menstrual cycle in the human.

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague-Dawley rat.

INTRODUCTION: It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague-Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented. METHODS: The aim of this study was to compare the potency of melatonin to limit the frequency of mammary cancer initiation with its potency to inhibit tumor progression once initiation, at 55 days of age, was achieved. The present study compared the effect of preventive treatment with melatonin (10 mg/kg daily) administered for only 15 days before the administration of DMBA with the effect of long-term (6-month) curative treatment with the same dose of melatonin starting the day after DMBA administration. The rats were followed up for a year after the administration of the DMBA. RESULTS: The results clearly showed almost identical preventive and curative effects of melatonin on the growth of DMBA-induced mammary ADK. Many hypotheses have been proposed to explain the inhibitory effects of melatonin. However, the mechanisms responsible for its strong preventive effect are still a matter of debate. At least, it can be envisaged that the artificial amplification of the intensity of the circadian rhythm of melatonin could markedly reduce the DNA damage provoked by DMBA and therefore the frequency of cancer initiation. CONCLUSION: In view of the present results, obtained in the female Sprague-Dawley rat, it can be envisaged that the long-term inhibition of mammary ADK promotion by a brief, preventive treatment with melatonin could also reduce the risk of breast cancer induced in women by unidentified environmental factors.

Long term inhibition by estradiol or progesterone of melatonin secretion after administration of a mammary carcinogen, the dimethyl benz(a)anthracene, in Sprague-Dawley female rat; inhibitory effect of Melatonin on mammary carcinogenesis.

A single intragastric administration of 7,12-dimethylbenz(a)anthracene (DMBA) has been shown to induce mammary tumors in young cycling female Sprague-Dawley rats. The appearance of the tumors is preceded by a series of neuroendocrine disturbances, including attenuation of the preovulatory Luteinizing Hormone surge and Gonadotropin-Releasing Hormone release and amplification of the preovulatory 17beta-Estradiol (E2) surge. In this study, we examined the hypothesis that a single administration of DMBA increases the E2 and Progesterone inhibition of the spontaneous and Isoproterenol-induced Melatonin (MT) secretion from the pineal gland, during the latency phase. Also, the incidence of mammary tumors, as well as the possible preventive effect of various doses of Melatonin, were recorded up to 6 months after daily administration. For all studies, Sprague-Dawley rats, 55-60 days of age, received, on the Estrous day of the Estrous cycle, a single dose of 15 mg DMBA delivered by intragastric intubation. For the study on ovarian steroids, they were ovariectomized 5 days later and then sacrificed by decapitation at 10 a.m., one month later. Pineal glands were removed and placed in perifusion chambers containing Hanks 199 medium. The medium was saturated with O2/CO2 (95%/5%) and its pH was 7.4. Ten independent chambers were immersed in a water bath at 37 degrees C. Each pineal gland received medium (flow rate: 0.16 ml/min) through a system of input lines. The fractions were collected every 10 min, and immediately frozen at -20 degrees C until Melatonin RIA. Experiments were repeated to obtain up to five experimental points for each treatment. E2 (10(-11)-10(-9) M) and Progesterone (10(-9)-10(-7) M) were applied during the entire perifusion period (7 h). Isoproterenol (10(-6) M) was applied for 20 min after 2.5 h in perifusion. Melatonin concentrations and Areas Under the Curves were compared using two-factor ANOVA as well as parametric or nonparametric two-sample methods after testing sample normality. For the study on the possible preventive effect of Melatonin, they were daily treated, by the intragastric route, with increasing doses of Melatonin for 6 months. The percentage of female rats having at least one mammary carcinoma were compared using the Fischer exact t-test. During the latency phase, in vehicle-treated rats, E2 and Progesterone treatments lead an almost significant inhibition of the Isoproterenol-induced stimulation of Melatonin secretion. In DMBA-treated rats, E2 treatment leads to a complete blunting of the Isoproterenol-induced stimulation of Melatonin and Progesterone treatment leads to a cyclic inhibition of the Isoproterenol-induced Melatonin secretion. During the promotion phase, there was a dose-dependent inhibitory effect (up to 65% inhibition) of the daily administration of Melatonin, on mammary tumors occurrence. In conclusion, the long term inhibition of DMBA upon Melatonin secretion from the pineal gland might accelerate the promotion of mammary tumors induced by the mammary carcinogen. Inversely, the daily administration of Melatonin for 6 months induces a long lasting protective effect against the formation of mammary tumors.

Timing of initiation of the preovulatory luteinizing hormone surge and its relationship with the circadian cortisol rhythm in the human.

The relationship between the hypothalamo-pituitary-gonadal (HPG) axis and the hypothalamo-pituitary-adrenal (HPA) axis has been well documented in the rat. In most cases, a negative coupling was observed and an inhibitory effect of the HPA axis upon the HPG was shown. In the female rat, a marked circadian rhythm of corticosterone plasma values is observed during each day of the estrous cycle, with maximal values around 08:00 p.m. The preovulatory luteinizing hormone (LH) surge also occurs at 08:00 p.m. on the day of proestrus. Here we measured circadian variations of plasma cortisol in humans in relation with the time of initiation of the preovulatory LH surge. Blood samples were taken at 08:00 a.m., 12:00 a.m., 04:00 p.m., 08:00 p.m., 12:00 p.m., and 04:00 a.m. from 19 subjects for 4 consecutive days, once 17beta-estradiol (E(2)) values reached 125 pg/ml (days 7-10 of the menstrual cycle). Serum E(2) and LH determinations were performed by microparticle enzyme immunoassays. Serum progesterone and plasma cortisol determinations were made using RIA methods. For plasma cortisol values, a marked circadian rhythm, with 2- to 3-fold higher values during the morning than during the afternoon, was almost identical before, during and after the LH surge. However, values were generally higher during the follicular phase than during the luteal phase. Maximum cortisol values occurred between 04:00 and 08:00 a.m. and minimal cortisol values between 04:00 and 08:00 p.m. Initiation of the LH surge (50% over the mean of previous values) occurred at 04:00 a.m. (20% of the cases) or at 08:00 a.m. (80% of the cases). There was a strong coupling between the onset of the surge and the acrophase of the cortisol circadian rhythm: maximal cortisol plasma values were seen at 04:00 a.m. when the LH preovulatory surge started at 04:00 a.m. and 08:00 a.m. when it started at 08:00 a.m. The present results show that the positive coupling documented in the female rat between the HPA and the HPG axis at the time of preovulatory LH surge is also present during the menstrual cycle in the human.