Is pineal melatonin released in the third ventricle in humans? A study in movement disorders.

In order to determine sources and metabolism of melatonin in human cerebrospinal fluid (CSF), melatonin and 6-sulfatoxymelatonin (aMT6S) concentrations were measured in CSF sampled during neurosurgery in both lateral and third ventricles in patients displaying movement disorder (Parkinson's disease, essential tremor, dystonia or dyskinesia) and compared with their plasma levels. Previous determinations in nocturnal urine had showed that the patients displayed melatonin excretion in the normal range, compared with healthy controls matched according to age. A significant difference in melatonin concentration was observed between lateral and third ventricles, with the highest levels in the third ventricle (8.75±2.75pg/mL vs. 3.20±0.33pg/mL, P=0.01). CSF aMT6s levels were similar in both ventricles and of low magnitude, less than 5pg/mL. They were not correlated with melatonin levels or influenced by the area of sampling. Melatonin levels were significantly higher in third ventricle than in the plasma, whereas there was no difference between plasma and lateral ventricle levels. These findings show that melatonin may enter directly the CSF through the pineal recess in humans. The physiological meaning of these data remains to be elucidated.

Unconjugated bisphenol A cord blood levels in boys with descended or undescended testes.

BACKGROUND: Human toxicity of bisphenol A (BPA), a weak estrogenic environmental endocrine disrupting compound, widely used in plastics, baby bottles, cans and dental sealants, is under investigation. Fetal or perinatal exposure in rodents is associated with programmed adult reproductive diseases. Human epidemiological studies remain scarce, especially concerning testicular development. We have investigated the relationship between fetal exposure to BPA and cryptorchidism. METHODS: Using a radioimmunoassay performed after extraction, validated by high-performance liquid chromatography and mass spectrometry, active levels of unconjugated BPA (uBPA) in cord blood (CB) were measured in 152 boys born after 34 weeks gestation, with cryptorchid or descended testes. RESULTS: Active uBPA was detectable in all CB samples, with values in the control group (n = 106) of 0.14-4.76 ng/ml, median: 0.9 ng/ml; mean ± SD: 1.12 ng/ml ± 0.86 ng/ml, which did not differ from cryptorchid boys (n = 46, 1.26 ± 1.13 ng/ml, P = 0.38). uBPA in controls correlated with CB inhibin B (P < 0.01) and total testosterone (P < 0.05), and with maternal milk polychlorinated bisphenyl 138 (P < 0.03). uBPA did not correlate with clinical maternal or fetal parameters or with other steroid or polypeptide CB hormones assessed. CONCLUSIONS: The presence of uBPA in all CB samples suggests placental transfer and fetal exposure. Similar uBPA levels in the control and cryptorchid groups make the participation of fetal exposure to uBPA in the physiopathology of undescended testes unlikely. However, the observed nanomolar uBPA concentrations support assessment of epidemiological relationships between CB uBPA and other human diseases.

Effect of constant light on prolactin and corticosterone rhythms evaluated using a noninvasive urine sampling protocol in the rat.

Circadian prolactin and corticosterone rhythms are usually investigated in the rat by analysis of plasma hormone profiles. In order to develop a nonstressful methodology for long-term studies, we validated prolactin and corticosterone radioimmunoassays in rat urine samples. Among the criteria of validation, prolactin was identified in urine by Western blot whereas both prolactin and corticosterone levels were undetectable in the urine of hypophysectomized rats. The determination of prolactin and corticosterone levels on serial urine samples showed daily variations in male rats entrained by the light-dark cycle. The acrophases of the 24-hour prolactin and corticosterone profiles were located at 03:26 h and 23:32 h respectively, a delay of 3-4 hours compared with the values of the 24-hour plasma profiles reported in the literature. Corticosterone and prolactin rhythms were abolished or dramatically delayed after 3 weeks of constant illumination. As expected, constant light suppressed the rhythm of 6-sulfatoxymelatonin, the major hepatic metabolite of melatonin. The noninvasive and nonstressful methodology we developed could be of interest for studying the regulation of hormone rhythms and their mutual endocrine interactions in physiological conditions, especially their evolution in the aging process.

Occurrence of hyperhomocysteinemia 1 year after gastroplasty for severe obesity.

Severe obesity exposes one to an increased risk of cardiovascular mortality. Gastroplasty has been shown to induce substantial weight loss and to improve the atherogenic profile of severely obese subjects. However, vitamin deficiencies after gastroplasty have been reported. Because hyperhomocysteinemia, an independent risk factor for cardiovascular disease, is influenced by nutritional status (and especially by folate intake), we hypothesized that a marginal folate deficiency induced by gastroplasty could promote hyperhomocysteinemia. Thus, plasma homocysteine concentrations were measured by high-performance liquid chromatography in 53 severely obese patients (body mass index = 42 +/- 1), before and 1 yr after vertical gastroplasty. Plasma homocysteine concentrations increased, on an average, from 9.9 +/- 0.4 to 12.8 +/- 0.6 micromol/L (P < 0.0001). This increase in homocysteine levels was observed in two thirds of the subjects, leading to clear-cut hyperhomocysteinemia (>15 micromol/L) in 32%. The changes in homocysteine concentrations were correlated to weight loss (P < 0.001) and to decrease in plasma folate concentrations (P < 0.01). Whereas gastroplasty induced a mean 32-kg weight loss and a striking improvement in conventional risk factors, the occurrence of iatrogenic hyperhomocysteinemia might hamper the benefit of surgery on cardiovascular risk in most of the patients. Our results further support use of a systematic efficient folate supplementation after gastroplasty.

Heterogeneity of human prolactin. Influence on immunoassays (RIA and IRMA).

Plasma hPRL consists of a complex mixture of molecular forms. The monomeric form, derived from the pituitary, is the main form. Others (dimeric or oligomeric) can form de novo in plasma. Recently, BBPRL (big big PRL) has been identified in some cases as an antiPRL autoantibody, but these data require further investigation. The PRL forms are differently recognized by immunoassays (IRMA and RIA) and are a source of inter-assay discrepancy.

Concanavalin-A-bound and -unbound prolactin in normal and hyperprolactinaemic rats.

Concanavalin-A (Con-A)-bound and -unbound forms of prolactin were studied in female Wistar-Furth rats, both normal and with hyperprolactinaemia induced by treatment with oestrogen or a prolactinoma graft. In normal rats, Con-A-bound prolactin was the major circulating form (more than 50%) and a minor pituitary component (less than 10%), essentially as 25 kDa prolactin. In oestrogen-treated rats, plasma prolactin levels were 100-fold higher and pituitary weight was fivefold higher than in the controls, but total pituitary prolactin content was unmodified. Under oestrogen, Con-A-bound prolactin represented about one-third of the total hormone levels in the plasma and less than 10% in the pituitary. In the pituitary, bound prolactin was found essentially as 25 kDa and unbound prolactin as 22, 30 and 40-45 kDa. A similar increase in plasma prolactin levels was induced 6 months after the graft of a prolactinoma. Pituitary weights and total pituitary prolactin contents were slightly decreased. Plasma and pituitary Con-A-bound prolactin levels were similar to those observed in oestrogen-treated rats. On the other hand, unbound prolactin was only present as a 22 kDa monomer. In the tumour, Con-A-bound prolactin (essentially as 25 kDa prolactin) represented one-third of the total hormone level and unbound prolactin was composed of the 22 and 45 kDa forms, this latter form being partially transformed into 22 kDa by heating.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct radioimmunoassay of 6-sulfatoxymelatonin in plasma with use of an iodinated tracer.

We describe here a direct a radioimmunoassay (RIA) for the determination of 6-sulfatoxymelatonin (aMT6s) in plasma, with iodinated aMT6s as tracer. The aMT6s antiserum was raised in rabbit by immunization with a bovine serum albumin conjugate, giving negligible cross-reactivities for related compounds. The low limit of detection (15 pmol/L) allowed a direct assay that required only a 100-microL plasma sample. Dilutions of plasma and of synthetic aMT6s gave the same parallel response in the RIA. A preliminary study showed a circadian variation in healthy volunteers, with mean concentrations ranging from 52 (at 1600-2100 h) to 378 pmol/L (at 0400 h), whereas this rhythm was abolished in pinealomectomized patients. After administration of melatonin orally, or by infusion, the aMT6s concentrations in plasma concorded with previous data on aMT6s production and pharmacokinetics, with aMT6s being cleared from plasma more slowly than melatonin. This assay should have practical application in the development of new pharmaceutical formulations that minimize the hepatic metabolism of melatonin.

Brain autoradiographic study in the golden hamster after intracarotid injection of [14C]melatonin.

The distribution of [14C]melatonin [( 14C]MT) after systemic injection was studied in the plasma and brain of golden hamsters. Thin-layer chromatographic analysis indicated that the radioactivity of the biological samples taken at two different times following the injection of label was exclusively associated with [14C]MT. Representative autoradiograms revealed a heterogeneous localization of [14C]MT in the grey matter. Two min after injection, the highest regional values were found in the hippocampus, caudate-putamen, medial thalamus and choroid plexuses. Lower radioactive concentrations were observed in the cingulate and frontoparietal cortex, anterior thalamus, inferior colliculus, dorsolateral geniculate nucleus, lateral and medial hypothalamus and amygdala. Fifteen min after injection, a significant level of radioactivity remained in the hippocampus, caudate-putamen, ventral thalamus and hypothalamus area. The heterogeneous distribution and the partial retention of [14C]MT in the brain are compatible with the existence of specific brain binding sites for this hormone.

Plasma, cerebrospinal fluid, and brain distribution of 14C-melatonin in rat: a biochemical and autoradiographic study.

The distribution of 14C-Melatonin (14C-MT) after systemic injection was studied in the plasma, cerebrospinal fluid (CSF), and brain of rats. Chromatographic analysis (thin-layer chromatography and high-performance liquid chromatography) indicated that the radioactivity from biological samples taken at various times following the injection of label was mainly associated with 14C-MT. Computer analysis of plasma 14C-MT kinetics showed a three-compartment system with half-lives of 0.21 +/- 0.05, 5.97 +/- 1.11, and 47.52 +/- 8.86 min. The volume of distribution and the clearance were 1,736 +/- 349 ml.kg-1 and 25.1 +/- 1.7 ml.min-1.kg-1 respectively. The entry of 14C-MT into the CSF was rapid and reached a maximum at 5 min. The decay followed a two-compartment system with half-lives of 16.5 +/- 2.9 and 47.3 +/- 8.6 min. The CSF/plasma concentration ratio was 0.38 at the steady state (30 min). At 2 min the level of 14C-MT in the brain was 3.8 higher than in the CSF. Representative autoradiograms revealed an heterogeneous localization of 14C-MT in the grey matter. The highest regional values, as evaluated by the permeability area product technique, were found in cortex, thalamic nuclei, medial geniculate nucleus, anterior pretectal area, paraventricular nucleus of the hypothalamus, choroid plexuses, and bulb-pons. Thirty minutes later 14C-MT was still detected in most of the brain regions analyzed. These results point to a low but rapid penetration of circulating MT into the brain and the CSF. The heterogeneous distribution and the partial retention of 14C-MT in the brain are compatible with the hypothesis of a central action of this hormone mediated via binding sites.

Pharmacokinetics of human growth hormone releasing factor (hGRF-44 NH2) in normal men after intravenous administration of a large range of doses.

Three ranges of doses of growth hormone releasing factor (2.5-80 micrograms, 80-320 micrograms and 75-600 micrograms) were intravenously administered to healthy young volunteers in three double blind studies. Serum circulating GRF levels were determined by radioimmunoassay. Experimental concentration curves were fitted, using the extended least squares method, to a biexponential model for the structural model and power function for the variance model. The power variance model, compared to the constant variance model greatly reduced the coefficient of variation of the biexponential parameters. The power of the variance model was estimated to be 1.95. The distribution half-life was 6.6 min and the elimination half-life was 39.0 min (harmonic means). Total clearance was 0.12 +/- 0.01 microgram/l/min. No difference between these parameters was found for the various doses. GRF kinetics was linear established in the range 10 to 600 micrograms which means that elimination was not altered by the increased doses.