Relationships between COL2A1 gene polymorphisms and knee osteoarthritis in Han Chinese women

To investigate the relationships between two COL2A1 single nucleotide polymorphisms (SNPs; T2088C and G4006A) and osteoarthritis (OA) in Han Chinese women. One hundred and twenty OA women and 120 control women were recruited. Genomic DNA was extracted from the whole blood. The COL2A1 polymorphisms T2088C and G4006A were analyzed by TaqMan assay. The levels of plasma N-propetide of type IIA collagen (PIIANP) and urinary C-telopeptide of type IIA collagen (CTX-II) were determined by ELISA. The level of plasma PIIANP significantly decreased in the OA group, compared with that in the control group (P < 0.05), with 15.6 ± 4.2 ng/ml (Mean ± SD) in the OA group and 30.2 ± 7.8 ng/ml in the control group. The level of urinary CTX-II significantly increased in the OA group, compared with that in the control group (P < 0.05), with 201.4 ± 10.2 ng/ml in the control group and 250.8 ± 15.6 ng/ml in the OA group. There was no difference in the T2088C genotypes between the OA and control groups. The G4006A AA homozygous genotype significantly increased in the OA patients, when compared with that in the control women (P < 0.05, χ²), with 24.2% (29/120) in the OA group and 10.0% (12/120) in the control group; The A allele accounted for 49.2% (118/240) in the OA group and 35.8% (86/240) in the control group. Among the G4006A genotypes, the plasma PIIANP level of the AA genotype (16.4 ± 6.6 ng/ml) was significantly lower than those of the GG genotype (28.6 ± 4.2 ng/ml) and GA genotype (21.5 ± 8.0 ng/ml) while the urinary CTX-II level of the AA genotype (255.2 ± 18.4 ng/ml) significantly increased, compared with those of the GG genotype (218.4 ± 13.2 ng/ml) and GA genotype (221.2 ± 15.6 ng/ml). The haplotype analysis shows that T-G was a protective factor for OA and that T-A was a risk factor. The AA genotype, A allele and T-A may increase the risk of OA in the Han Chinese women while T-G may protect these women from OA.     

The influence of prolactin (PRL) on progesterone secretion by porcine luteal cells in vitro

Porcine luteal cells were obtained from corpora lutea on the 5th, 13th and 17th days of the estrous cycle. The cells were suspended at a concentration of 5 × 10⁴ cells/ml in Eagle's medium with 2% human serum albumin. These cells were incubated with or without 0.01, 0.1, 1 or 10 μg/ml porcine prolactin. The amount of progesterone in cultures was estimated by a radio-immunological method after 30 min, 3 h and 6 h of culturing.Luteal cells obtained on the 5th day of the estrous cycle and incubated without prolactin secreted 71.24 ± 21.91 ng progesterone/ml of medium, whereas under the influence of prolactin at 0.01, 0.1, 1 and 10 μg/ml, 39.06 ± 13.33, 44.31 ± 12.69, 44.88 ± 16.85 and 51.62 ± 15.01 ng progesterone/ml (P<0.01) were secreted. Luteal cells from the 13th day of the estrous cycle incubated without prolactin secreted on average 70.72 ± 9.21 ng progesterone/ml of medium, whereas under the influence of different prolactin doses 50.75 ± 8.52, 46.54 ± 7.13, 43.30 ± 6.78 and 41.68 ± 7.21 ng progesterone/ml (P<0.01) were secreted.Prolactin did not change progesterone secretion by luteal cells obtained on the 17th day of the estrous cycle. An influence of the incubation time on progesterone secretion by these cells was observed: after 30 min of incubation the cells secreted 8.83 ± 2.95 ng/ml, after 3 h 8.12 ± 2.57 ng/ml and after 6 h 6.86 ± 1.91 ng/ml, irrespective of the amount of PRL added.The results suggest that prolactin plays a role in the luteolysis of the corpus luteum.     

Simultaneous occurrence of pregnancylike lobuloalveolar morphogenesis and casein-gene expression in a culture of the whole mammary gland

Summary Entire second thoracic mammary glands of estrogen- and progesterone-treated immature virgin BALB/c mice were stimulated to pregnancylike lobuloalveolar morphogenesis after 6 days of incubation with insulin (5 μg/ml), aldosterone (1 μg/ml), growth hormone (5 μg/ml), cortisol (5 μg/ml), and prolactin (80 ng/ml, present as a contaminant in 5 μg/ml growth hormone). The alveolar growth in the glands, as judged by morphological studies, was accompanied by an increase in cell number as a function of incubation time in the hormonal medium. Hybridization of the total RNA from these glands to the casein mRNA specific complementary DNA probe (cDNA_csn) revealed that the level of casein mRNA rises from 0.00012 to 0.005% between 1 and 6 days of incubation. Estimates showed that the concentration of casein mRNA per cell rises 17-fold from 70 molecules on Day 1 to 1200 molecules on Day 6, whereas the number of epithelial cells increases only twofold during the same incubation time. When the growth hormone preparation was totally replaced by 80 ng of prolactin during the 6-day incubation, casein-mRNA levels were found to be 0.0083%. These results demonstrate that a pregnancy-like morphogenesis and concurrent expression of the casein gene in vitro can be achieved in a controlled hormone environment containing high cortisol and low prolactin concentrations. This one-step mammogenesis-lactogenesis culture model should be useful for studying the mechanisms of hormonal regulation of casein-gene expression observed in prepartum mammary gland in vivo. This work was supported by Department of Health, Education and Welfare Grants CA11058 and CA25304 from the National Cancer Institute.     

Salivary Nickel and Chromium Levels in Orthodontic Patients with and Without Periodontitis: a Preliminary Historical Cohort Study

Many periodontal patients may need orthodontic treatment. Alterations in oral environment particularly the reduction of pH in periodontal patients could affect metal ion release from orthodontic appliances. However, there is no study on metal ion release in periodontal patients. The aim of this preliminary study was to comparatively evaluate, for the first time, salivary levels of nickel and chromium in periodontal patients (versus healthy controls) under orthodontic treatment for 2 months. In this in vivo study, 40 subjects were evaluated. Patient selection and standardization of orthodontic treatment protocols were prospectively designed and performed. Two groups of n = 20 each (control: healthy orthodontic patients, cohort: orthodontic patients with periodontitis) underwent similar protocols of fixed orthodontic treatment for 2 months. After 2 months, salivary nickel and chromium concentrations of the case and cohort groups were measured using inductively coupled plasma mass spectrometry (ICP-MS). The values were compared between the two groups using t test. There were 10 men and 10 women in each group. The mean age of patients was 34.6 ± 3.6 years old. The salivary level of nickel was 338.2 ± 235.5 ng/ml and 182.8 ± 116.5 ng/ml in the cohort and control groups, respectively (P = 0.0118). The salivary level of chromium was 7.4 ± 3.15 ng/ml in the cohort and 6.35 ± 2.39 ng/ml in the control group (P = 0.2214). Salivary level of nickel might be considerably higher in periodontal patients undergoing 2 months of orthodontic treatment compared to orthodontic patients with healthy gingivae.

     

Measurement by radioimmunoassay of casein content in rabbit mammary gland during pregnancy and after prolactin stimulation in organ culture

A specific homologous radioimmunoassay was developed to measure rabbit beta-casein in rabbit mammary gland with a sensitivity of 0.5 ng/ml protein. It was used to measure casein concentration during pregnancy and in organ culture of mammary gland explants. Casein was detectable in virgin mammary glands, showed a small increase during the first half of pregnancy, increased more than 20-fold between Days 21 and 27, and diminished somewhat on the first days of lactation. After 24 hr of culture, mammary gland explants had no detectable casein, but the addition of increasing concentrations of prolactin to a culture medium which contained insulin (5 micrograms/ml) and cortisol (0.5 microgram/ml) induced a regular increase in the casein content of the tissue. Casein started to increase when 10 ng/ml of prolactin was present and maximal values were achieved for 100 ng/ml of the hormone.     

Plasma luteinizing hormone and prolactin in normothermic and hyperthermic ovariectomized ewes

The effect of bromocriptine on concentrations of luteinizing hormone (LH) and prolactin (PRL) as well as the rhythmicity of episodic profiles of plasma LH were investigated in twelve ovariectomized ewes exposed to 3-day trials during which ambient temperature/humidity conditions maintained either normothermia or induced an average of 1.4°C increase of rectal temperature (hyperthermia). In 24 of 48 trials, ewes received twice daily subcutaneous injections of 1 mg bromocriptine beginning at 1900 hr on day 1. Plasma PRL and LH were measured at 10-min intervals for 4 hr on days 2 and 3. Bromocriptine significantly decreased plasma PRL (65 ± 6 vs 5 ± 1 ng/ml), mean plasma LH (11.0 ± 0.2 vs 6.5 ± 0.2 ng/ml) and tended (P < 0.1) to decrease LH rhythmicity. In hyperthermic placebo-treated ewes, plasma PRL was increased (65 ± 6 vs 212 ± 20 ng/ml) and mean LH was decreased (11.0 ± 0.2 vs 8.2 ± 0.2 vg/ml) compared to normothermic, placebo-treated ewes, but there was no effect of hyperthermia on LH rhythmicity. Bromocriptine treatment of hyperthermic ewes decreased mean PRL (212 ± 20 vs 32 ± 9 ng/ml) on both days of sampling although mean levels were significantly higher on day 2 than on day 3(54 ± 14 vs 10 ± 6 ng/ml). Perhaps because mean LH was already inhibited in hyperthermic ewes, bromocriptine did not further decrease mean LH (8.2 ± 0.2 vs 6.6 ± 0.2 ng/ml), but LH rhythmicity was decreased (P < 0.01). There was no significant difference in mean LH between normothermic ewes receiving bromocriptine and hyperthermic ewes receiving bromocriptine (6.5 ± 0.2 vs 6.6 ± 0.2 ng/ml). These results indicate that bromocriptine inhibits PRL and LH secretion in normothermic ewes. In hyperthermic ewes, the inhibitory effect of bromoriptine on PRL was even more pronounced, but the effect on LH release was minimal perhaps because LH was already inhibited by hyperthermia.     

Homogeneous distribution of prolactin in human cerebrospinal fluid

Concentrations of prolactin were assayed from human cerebrospinal fluid (CSF). Samples were taken from lumbar CSF space (n=105 neurological patients) and from lateral ventricles (n=31 neurosurgical patients). Ventricular CSF samples were taken from operatively treated subarachnoidal hemorrhage (SAH) patients during the monitoring of intraventricular pressure. More voluminous and frequent sampling was obtained from six patients undergoing diagnostic pneumoencephalography (PEG) procedure. Prolactin concentrations in lumbar CSF ranged between undetectable and 2.8 ng/ml with a mean value of 0.78±0.54 (SD) ng/ml. Some fluctuation was seen in the fractionated samples taken at PEG, but no definitive gradient was noticed. Ventricular CSF concentrations of prolactin (n=18) were 0.85±0.67 (SD) ng/ml at operation (range : undetectable ? 2.5 ng/ml). Somewhat lower values were recorded in the 3-day postoperative period, prolactin mean concentrations being 0.3 ? 0.6 ng/ml. The CSF prolactin concentrations in the lateral ventricles and lumbar sac are practically identical with no concentration gradient between these compartments.     

Inhibition of casein synthesis by progestagens in vitro: modulation in relation to concentration of hormones that synergize with prolactin

We studied the effect of progesterone and its agonist, R 5020, on casein and transferrin production in pregnant rabbit mammary gland explant culture and its modulation by hormones that synergize with prolactin. The glands were obtained from rabbits on days 12-14 of gestation. The progestins had no effect alone, but significantly inhibited ovine and porcine prolactin stimulation of casein synthesis in a dose dependent manner. There were no effects on transferrin content of the tissue, demonstrating a specific effect of progesterone on casein synthesis. In approx 15% of the cultures, prolactin stimulated casein production to very high levels and the progestins lost their inhibitory action. Progestins were also ineffective when the tissue was cultured with prolactin and unphysiologically high levels of insulin (5 mg/l) or cortisol (280 nmol/l), which stimulated casein synthesis to higher levels than prolactin alone. The concentration of cortisol used was 10 times higher than the serum levels seen in rabbits at the stage of gestation studied (approx 10 ng/ml) and corresponded to levels seen at the end of gestation, a period when the glands are secreting milk and progesterone serum levels have commenced to decrease. Thus, when the prolactin effect upon casein synthesis had been potentiated, whether spontaneously or through synergism with insulin or corticoids, progestins were unable to inhibit it, as is the case in lactating tissues. The results show that utilization of unphysiological levels of hormones in culture may distort the response of the tissue, masking responses that are clearly seen in vivo.     

Control of mammary gland fibroblast growth by insulin, growth hormone and prolactin

Fibroblasts isolated from guinea pig mammary glands were cultured in 96 well culture plates in the presence of various concentrations of insulin, growth hormone and prolactin. Insulin (30 micrograms/ml increased uptake of tritiated thymidine by 30%. Higher concentrations of insulin did not result in any further increase in thymidine uptake. Growth hormone alone did not alter thymidine uptake in concentrations of 0 to 250 ng/ml. 300 ng/ml gave thymidine uptake of 136% of controls. In the presence of 20 g/ml insulin, growth hormone (250 ng/ml) increased thymidine uptake to approximately double that of controls. Prolactin alone (300 ng/ml decreased thymidine uptake by 19%. Insulin increased thymidine uptake, but the negative effect of prolactin was still evident above 150 ng/ml.     

Growth and Differentiation of Primary Cultures of Mouse Mammary Epithelium Embedded in Collagen Gel

Mammary glands from BALB/cfC3H midpregnant (9–11 days) mice were dissociated with collagenase and pronase, separated on a Percoll gradient, and the epithelial cells were cultured inside collagen gel. The cell number increased three-to five-fold when cultured for 6–8 days in DME/F12 (1: 1) medium containing 3% swine serum, insulin (10 μg/ml), cortisol (1.0 μg/ml), prolactin (10 μg/ml), transferrin (10 μg/ml), and epidermal growth factor (0.01 μg/ml). The casein level, as determined by radioimmunoassay, at the end of this growth phase, was much lower than that present in freshly dissociated cells. In order to stimulate casein production, the gels were released from the sides of the plastic dish and allowed to float for eight days in Waymouth's medium, containing insulin (10 μg/ml), cortisol (5 μg/ml), prolactin (10 μg/ml), and 0.25% bovine serum albumin. The casein level at the end of this differentiation phase was found to be comparable to that seen in the original freshly dissociated cells. Cells grown in DME/F12 (1: 1) medium containing 3% swine serum, insulin (10 μg/ml), and transferrin (10 μg/ml) were still capable of undergoing casein production, indicating that the presence of exogenous lactogenic hormones such as cortisol and prolactin, as well as exogenous growth factors such as epidermal growth factor, is not necessary during the growth phase for subsequent casein production during the differentiation phase. Two factors that seemed more important for subsequent casein stimulation were: (1) releasing collagen gels at the beginning of the differentiation phase, and (2) switching to'differentiation' medium. This present two-step protocol has allowed primary cultures of dissociated midpregnant mouse mammary epithelial cells to undergo several rounds of division inside a collagen gel matrix and to be subsequently stimulated to produce the mammary-specific protein, casein.     

Concentrations of LH,prolactin and progesterone in early-pregnant and oestradiol-treated pigs

Fifteen gilts (n = 5 per group) were used to study plasma LH, prolactin and progesterone concentrations on days 13–19 after oestrus in early-pregnant, oestradiol-treated (5 mg, administered on days 11–15) and control cycling pigs.Peripheral blood samples were taken without stress at one-hour intervals for 12 h on days 13–14, 15–16 and 18–19. There was no difference amongst groups in LH levels on days 13–14 and 15–16. The LH levels in the cycling untreated pigs was lower (P < 0.05) than in pregnant gilts on days 18–19. Concentrations of prolactin in oestradioltreated pigs were 7–20 times higher than in pregnant pigs. The greatest differences in progesterone concentrations were recorded on days 18–19. Progesterone levels were less (P < 0.01) in oestrogen-treated gilts (14.54±1.09 ng/ml) when compared with pregnant gilts (24.23 ± 4.10). A comparison of the secretion patterns for the three hormones showed that injections of oestradiol given to the cycling gilt did not result in patterns which fully imitate the implantation period of natural pregnancy in the pig.     

Mannose-Binding Lectin Serum Levels are Low in Persons with Clinically Active Coccidioidomycosis

Background  Mannose-binding lectin (MBL) is a circulating collectin that is part of the innate immune response. We explored the serum levels of MBL in persons with different forms of coccidioidomycosis. Methods  Serum MBL was measured by ELISA from samples obtained from healthy donors with immunity to Coccidioides, and those with various forms of active coccidioidomycosis. Blood cell specimens from a subgroup of subjects with active coccidioidomycosis were examined for single nucleotide polymorphisms of the MBL gene and promoter regions. Results  The control group comprised 29 healthy immune subjects. Patient groups with active coccidioidomycosis consisted of 20 patients with symptomatic primary pulmonary coccidioidomycosis, 26 with non-meningeal disseminated coccidioidomycosis, and nine with coccidioidal meningitis. The group with active coccidioidomycosis was significantly older and more likely to be male than the control group (for both, P < 0.001). The mean ± SEM level of serum MBL in the healthy controls was 169.4 ± 28.6 ng/ml, significantly higher than the 79.2 ± 10.9 ng/ml for all active groups (P < 0.001). Moreover, the active coccidioidomycosis group was significantly more likely to have serum MBL level ≤70 ng/ml compared to the control group (P = 0.001). Genetic analysis in 27 subjects with active coccidioidomycosis revealed marked variation based on race and ethnicity. Among a subgroup of 10 white, non-hispanic men with active coccidioidomycosis, there was a significant association between the H and P haplotypes and MBL levels ≤70 ng/ml (P < 0.036 and P < 0.035, respectively). Conclusions  These data suggest that there is an association between low serum MBL levels and symptomatic coccidioidomycosis.     

Primary culture of normal rat mammary epithelial cells within a basement membrane matrix. I. Regulation of proliferation by hormones and growth factors

Summary A serum-free primary culture system has been developed which allows for three-dimensional growth and differentiation of normal rat mammary epithelial cells (RMECs) within an extracellular matrix preparation. RMECs were isolated from mamary glands of immature 50- to 60-d-old rats and the organoids embedded within a reconstituted basement membrane matrix prepared from the Engelbreth-Holm-Swarm sarcoma. Cells grown in a serum-free media consisting of phenol red-free Dulbecco's modified Eagle's medium-F12 culture medium containing 10 μg/ml insulin, 1 μg/ml prolactin, 1 μg/ml progesterone, 1 μg/ml hydrocortisone, 10 ng/ml epidermal growth factor (EGF), 1 mg/ml fatty-acid-free bovine serum albumin (BSA), 5 μg/ml transferrin, and 5 μM ascorbic acid proliferated extensively (15- to 20-fold increase in cell number as quantitated using the MTT dye assay) over a 2- to 3-wk culture period and remained viable for months in culture. Several types of colonies were observed including the alveolarlike budding cluster which predominates at later times in culture, units with no or various degrees of ductal-like projections, stellate colonies, and two-and three-dimensional web units. Optimal proliferation required insulin, prolactin, progesterone, EGF, and bovine serum albumin. Hydrocortisone was not required for proliferation, but the colonies developing in its absence were morphologically altered, with a high frequency of colonies that formed an extensively branched network with many fine projections. Cell proliferation was also dependent on substratum, with significantly less growth and development occurring in RMECs grown within a type I collagen gel matrix compared to RMECs grown within the reconstituted basement membrane. In conjunction with other studies demonstrating extensive differentiation as well as proliferation, it is concluded that this model should prove to be an improtant tool to study the hormonal regulation of the growth and development of rat mammary cells. This work was supported by grants CA 33240 and CA 35641 and by core grant CA 24538 from the National Institutes of Health, Bethesda, MD.     

Effect of Selenium Supplementation on Blood Status and Milk,Urine, and Fecal Excretion in Pregnant and Lactating Camel

Ten pregnant female camels divided into two groups received, after a 2-week adaptation period, an oral selenium (Se) supplementation (0 and 2 mg, respectively) under sodium selenite form for 6 months from the three last months of gestation up to the three first months of lactation. Feed intake was assessed daily. Blood samples and body weight were taken on a biweekly basis, both in dams and their camel calves after parturition. Feces and urine samples were collected monthly and milk on a biweekly basis. The Se concentration in serum increased significantly in the supplemented group and was threefold higher than the concentration compared to the control group, respectively, 305.9 ± 103.3 and 109.3 ± 33.1 ng/mL. The selenium concentration increased in similar proportion in milk (86.4 ± 39.1 ng/mL in the control group vs 167.1 ± 97.3 ng/mL in treated group), in urine, and feces. The gluthathione peroxidase (GSH-Px) activity varied between 18.1 ± 8.7 IU/g hemoglobin (Hb) in control group and 47.5 ± 25.6 IU/g Hb in treated group but decreased after parturition in both groups. Vitamin E did not change significantly and was, on average, 1.17 ± 0.72 and 1.14 ± 0.89 ng/mL in the control and treated groups, respectively. Significant correlations were reported between serum Se, milk Se, GSH-Px, and fecal and urinary excretion or concentration. Blood values in camel calves were similar to those of the dams. The results seemed to confirm the sensitivity of camel to Se supplementation with an important increase of selenium in serum and milk.     

Prolactin regulation of cryptic prolactin receptors in cultured rat mammary tumor cells

Rat mammary tumors contain a unique class of cryptic cell-surface prolactin receptors that can be unmasked by depleting the cells of energy. These cryptic receptors, which are found in mammary tumors and nonlactating normal mammary cells but not in differentiated mammary tissue, are continuously inserted and rapidly removed from the cell surface. In this report we demonstrate that prolactin regulates the level of cryptic receptors. Treatment of primary cultures of rat mammary tumor cells with prolactin at concentrations between 0.1 and 0.5 ng/ml caused cryptic receptor levels to increase within 24 h, and this increase was maintained for up to 6 days. At prolactin concentrations of 10-50 ng/ml, receptor levels were the same as in cells incubated without hormone, while a decrease in the steady-state level of cryptic receptors was induced within 24 h by 100-500 ng prolactin/ml. Concentrations of 1,000-5,000 ng prolactin/ml caused a rapid, dose-dependent down regulation of cryptic receptor sites. Down regulation at 5,000 ng prolactin/ml was (1) complete (84 +/- 5% reduction) in 1 h; (2) specific for lactogenic hormones; (3) completely reversed within 10 h after prolactin removal; (4) energy dependent; and (5) not blocked by the cytoskeleton active agents cytochalasin B and colchicine or by NH4Cl, which inhibits hormone degradation. We conclude that rat mammary tumor cells have the capacity to auto-regulate cryptic prolactin receptors, a property that supports our notion that such receptors play a role in regulating prolactin responsiveness. The observed pattern of cryptic receptor autoregulation in response to prolactin concentration and time of exposure suggests that a pool of cryptic sites provides these cells with the capacity to respond to prolactin concentrations from pg to microgram/ml, a range well beyond the Kd for the receptor itself. Since prolactin receptors in mammary tumors are not down regulated unless prolactin concentrations are well beyond the saturation point, these cells may have a selective growth advantage over cells in normal mammary tissue.     

The effect of prenatal photoperiodic history on the postnatal endocrine status of female lambs

Postnatal photoperiodic experience plays a pivotal role in determining the timing of ovarian activity in female lambs. This study examines whether a photoperiodic history gained while in utero is able to influence this timing.Pregnant Soay ewes were maintained in either long days (n = 7, 18 h light : 6 h dark; group PLD) or short days (n = 12, y h light : 18 h dark; group PSD) from 25 days of gestation. At birth, female lambs (n = 8 per group) were transferred to long days for 10 weeks, and then placed under short days until the end of the experiment at 38 weeks of age. Blood samples were collected from lambs on the day of birth and three times weekly for the duration of the study and the resulting plasma assayed for progesterone and prolactin.Although both gestational photoperiods produced, at best, abbreviated periods of ovarian activity, lambs born to ewes which experienced long days during gestation (group PLD) exhibited elevated plasma progesterone concentrations significantly earlier (P < 0.05) than lambs born to ewes exposed to short days during gestation (group PSD) (mean ± SEM, 193 ± 17 versus 244 ± 14 days for PLD and PSD groups, respectively. Plasma prolactin concentrations in newborn lambs born between late December and early April were not affected by the ambient photoperiod, but reflected the artificial daylength experienced by their mothers during gestation. Lambs born to ewes maintained under long days during gestation (group PLD) had significantly higher prolactin concentrations on the day of birth than lambs born to ewes maintained under short days during gestation (group PSD) (45 ± 5.4 ng/ml versus 7 ± 3.7 ng/ml respectively, P < 0.001). The mean birth weight, rate of live weight gain and live body weight of lambs at the end of the experiment did not vary significantly between treatment groups. These results suggest that the ovine foetus is sensitive to photoperiodic information prior to birth, and develops a photoperiodic history which, under the present experimental conditions, modulates the subsequent endocrine status of the neonatal lamb.     

Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women

Kraemer, R. R., L. G. Johnson, R. Haltom, G. R. Kraemer, H. Gaines, M. Drapcho, T. Gimple, and V. Daniel Castracane. Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women. J. Appl.Physiol. 84(2): 703-708, 1998.Exercise elevatesgrowth hormone (GH) and prolactin (PRL) blood concentrations inpremenopausal women. Postmenopausal women taking hormone replacementtherapy (HRT) maintain higher estrogen levels that could affect GH andPRL. The purpose of the study was to determine the effects of HRT on GHand PRL responses to treadmill exercise. Seventeen healthy women whowere postmenopausal (naturally or surgically) [8 on HRT; 9 not onHRT (NHRT)], completed 30 min of treadmill exercise at 79.16 ± 1.2% maximal O₂ consumption (HRT group) and 80.19 ± 0.91% maximalO₂ consumption (NHRT group). Bloodsamples were collected from an intravenous catheter during an exercisesession and during a control session without exercise. GH and PRLconcentrations were significantly higher in the exercise trial than inthe nonexercise trial, whereas resting concentrations were similar forboth trials. GH and PRL peaked at 10.8 ± 1.60 and 12.67 ± 2.58 ng/ml, respectively, for HRT subjects and at 4.90 ± 1.18 and 9.04 ± 2.17 ng/ml, respectively, for NHRT subjects. GH concentrations inthe exercise trial were significantly higher for HRT than for NHRTsubjects. This is the first study to demonstrate that HRT enhancestreadmill-exercise-induced GH release and that similar PRL responses totreadmill exercise occur in postmenopausal women regardless of HRTstatus.