The uterotrophic and antiuterotrophic activities of tamoxifen and 6-hydroxy-2-(p-hydroxyphenyl)-benzo(b)thien-3-yl p- <2-(1-pyrrolidinyl) ethoxyphenyl ketone (LY 117018) in the immature rat uterus have been evaluated. The antioestrogens were administered alone, concurrently or sequentially with or without oestradiol. LY 117018 administered alone was less uterotrophic (oestrogenic) than tamoxifen. At high doses, when administered concurrently with oestradiol, LY 117018 was more antiuterotrophic (antioestrogenic) than tamoxifen. When uterine growth was maximally stimulated by prior treatment with oestradiol, tamoxifen and LY 117018 were equally effective in reducing uterine weight. However, when uterine growth was induced with a dose of oestradiol producing an oestrogenic effect equivalent to that of tamoxifen (but less than that produced by LY 117018) LY 117018 was more effective than tamoxifen in reversing the uterotrophic effect of oestradiol. In animals pretreated with LY 117018 a further increase in uterine weight occurred on treatment with tamoxifen. The increase in uterine weight after tamoxifen was progressively reversed by increasing doses of LY 117018. The hypothesis that tamoxifen and LY 117018 may act by different mechanisms, based on the apparent failure of LY 117018 to antagonize the uterotrophic action of tamoxifen, is not supported by these studies.

In prepubertal cattle, mammary development is characterized by the growth of an epithelial-rich parenchyma (PAR) into the mammary fat pad (MFP). This proliferation and accumulation of mammary epithelial cells require estrogen. Paradoxically, both epithelial cell proliferation and PAR accumulation rate decline with rising plasma estrogen as puberty approaches. The possibility that variation in abundance of estrogen receptors (ERs) in PAR or MFP accounts for a portion of these effects has not been examined in cattle. Additionally, we recently demonstrated that MFP is highly responsive to exogenous estrogen, suggesting that this tissue may play a role in coordinating estrogen’s effects on PAR; however, the developing bovine MFP has yet to be studied in detail. To address these hypotheses, Holstein heifers were assigned to planes of nutrition supporting body growth rates of 950 (E) or 650 (R) g/day and harvested every 50 kg from 100 to 350 kg body weight (BW). Post-harvest, their mammary glands were dissected into PAR and MFP compartments. Transcript abundance of genes encoding members of the ER family (ERα, ERβ, and estrogen-related receptor α-1 (ERRα)) and estrogen-responsive genes (IGF-I and progesterone receptor (PR)) were measured in both mammary compartments by quantitative real-time RT-PCR. Significant expression was detected for all genes in both compartments, with the exception of the ERβ gene. Transcript abundance of both ERα and IGF-I decreased linearly with increasing BW within both compartments. ERRα and PR expressions decreased with increasing BW in PAR but not in MFP. Nutrition stimulated ERα and ERRα expression in the PAR but had no effect on IGF-I or PR in either PAR or MFP. Overall, ERα and IGF-I transcript abundance are consistent with the drop in mammary epithelial cell proliferation and PAR accretion observed over development, but do not support a negative effect of nutrition on PAR growth.

Steroid receptors are key transcriptional regulators of mammary growth, development and lactation. Expression of estrogen receptors alpha (ERα) and beta (ERβ), progesterone receptor (PR), and estrogen-related receptor alpha-1 (ERRβ) have been evaluated in bovine mammary gland. The ERRα is an orphan receptor that, in other species and tissues, appears to function in the regulation of estrogen-response genes including lactoferrin and medium chain acyl-CoA dehydrogenase and in mitochondrial biogenesis. Expression of ERα, ERβ, PR and ERRα was characterized in mammary tissue obtained from multiple stages of bovine mammary gland development using quantitative real-time RT-PCR. Expression was evaluated in prepubertal heifers, primigravid cows, lactating non-pregnant cows, lactating pregnant cows and non-lactating pregnant cows (n=4 to 9 animals/stage). In addition, ERα, ERβ, PR and ERRα were mapped to chromosomes 9, 10, 15 and 29 respectively, by linkage and radiation hybrid mapping. Results indicated that expression of ERα, PR and ERRα was largely coordinately regulated and they were present in significant quantity during all physiological stages evaluated. In contrast, ERβ transcripts were present at a very low concentration during all stages. Furthermore, no ERβ protein could be detected in bovine mammary tissue by immunohistochemistry. The ERα and PR proteins were detected during all physiological states, including lactation. Our results demonstrate the presence of ERα, PR and ERRα during all physiological stages, and suggest a functional role for ERRα and a relative lack of a role for ERβ in bovine mammary gland development and lactation.

A reciprocal relationship between the endocrine and immune system has been demonstrated under pathophysiological conditions. However, few studies have assessed the relationship between thyroid hormones and immune function in apparently healthy individuals. Therefore, to clarify our understanding of normal physiological endocrine–immune interactions this study aimed to examine the interrelationships between thyroid hormones and immunity in healthy individuals. Total triiodothyronine (T₃), total thyroxine (T₄) and markers of immune status were assessed in 93 free-living and apparently healthy individuals aged 55–70 years. T₃ and T₄ concentrations were determined by commercially available kits. Immune status was assessed using flow cytometry and biochemical markers. Statistical analysis was performed by partial correlation, controlling for age. Thyroid hormone concentration was positively associated with markers of inflammation (P≤0.05), natural killer-like T cells (P≤0.001), expression of interleukin-6 (IL6) by activated monocytes (P≤0.05); percentage expression of memory T-lymphocytes (P≤0.01), memory T-helper lymphocytes (P≤0.05) and memory T-cytotoxic lymphocytes (P≤0.05), and higher IL2 receptor density on CD3+T-lymphocytes (P≤0.05). Thyroid hormone concentration was inversely associated with early lymphocyte apoptosis (P≤0.05) and the ratio of naïve- to memory T-cytotoxic lymphocytes (P≤0.05). The current study provides preliminary evidence of a role for T₃ and T₄, within normal physiological ranges, in the maintenance of lymphocyte subpopulations, and in mediating the inflammatory response. In conclusion, these findings highlight the potential implications of altered thyroid function in older individuals and the importance of future research examining thyroid–immune interactions.

Production and regulation of activin A and inhibin B during the cycle of the seminiferous epithelium were investigated in adult rats. Immunohistochemistry localised the activin β_A-subunit to the Sertoli cell cytoplasm, with much weaker expression in spermatocytes and spermatids. Both activin A and inhibin B, measured by ELISA were secreted by, seminiferous tubule fragments over 72 h in culture. Activin A was secreted in a cyclic manner with peak secretion from tubules isolated at stage VIII. Tubules collected during stage VI produced the least activin A. Inhibin B secretion was highest from stage IX-I tubules and lowest from stage VII tubules. Addition of interleukin-1β (IL-1β) had relatively little effect on activin A or inhibin B secretion in culture. In contrast, the peak secretion of activin A by stage VIII tubules was blocked by co-incubation with an excess of human recombinant IL-1 receptor antagonist, whereas inhibin B secretion increased slightly. Dibutyryl cAMP stimulated activin A secretion by late stage VII and VIII tubules and stimulated inhibin B across all stages. These data indicate that activin A and inhibin B are cyclically regulated within the seminiferous epithelium, with endogenous IL-1 (presumably IL-1α produced by the Sertoli cells), responsible for a peak of activin A production subsequent to sperm release at stage VIII. These data provide direct evidence that production of activin A and inhibin B by the Sertoli cell is locally modulated by IL-1α , in addition to FSH/cAMP, under the influence of the developing spermatogenic cells.

The regulation of Sertoli cell activin A and inhibin B secretion during inflammation was investigated in vitro. Adult rat Sertoli cells were incubated with the inflammatory mediators, lipopolysaccharide (LPS), interleukin-1β (IL-1β), IL-6 and the IL-1 receptor antagonist (IL-1ra) over 48 h in culture. Activin A, inhibin B and IL-1α were measured in the culture medium by specific two-site ELISAs. Both IL-1β- and LPS-stimulated activin A and inhibited inhibin B secretion. LPS also stimulated the production of IL-1α in the cultures. In contrast to IL-1β, IL-6 had no effect on activin A, although it did have a significant inhibitory effect on inhibin B secretion. Ovine follicle-stimulating hormone (FSH) and the cAMP analogue dibutyryl cAMP opposed the actions of IL-1 and LPS by suppressing activin A and IL-1α secretion and by stimulating inhibin B. Blocking IL-1 activity in the cultures by addition of an excess of IL-1ra completely prevented the response of activin A to exogenous IL-1β, and reduced the response to LPS by 50%. In the presence of IL-1ra, basal secretion of inhibin B was increased, but IL-1ra was unable to reverse the suppression of inhibin B by LPS. These data indicate the importance of both IL-1 isoforms in regulating secretion of activin A and inhibin B by mature Sertoli cells during inflammation. The data also establish that inflammation exerts its effects on activin A and inhibin B secretion via other pathways in addition to those mediated by IL-1, and that hormonal stimulation by FSH and cAMP moderates the Sertoli cell response to inflammation. Interference with the complex interactions between these cytokines and hormones may contribute to the disruption of reproductive function that can accompany infection and illness in men.

The release of activin A in response to intravenous injection of the bacterial cell-wall component lipopolysaccharide (LPS) was investigated in an ovine model of acute inflammatory challenge in newborn and adult sheep, and in non-pregnant and pregnant ewes. Neonatal lambs (<20 days of age) showed a quantitatively similar response in terms of circulating concentrations of activin A, its binding protein follistatin and the cytokine interleukin-6 compared with adult ewes challenged with an equivalent dose (300 ng/kg bodyweight) of LPS. The fever response and plasma tumour necrosis factor-α release in response to LPS, however, were significantly (P < 0.01) less in lambs than in the adult group. Pregnant ewes in the last trimester of gestation had similar responses to LPS, in all aspects measured, compared with their non-pregnant counterparts, apart from an ablated fever response. Although the adult and neonatal sheep responded to LPS, a similar response was not apparent in the fetal circulation, possibly due to a protective effect of the placenta. A 10-fold increase in the dose of LPS (from 300 ng to 3 μg/kg bodyweight) given to neonatal lambs elicited an increase in several cytokine responses measured, with a significant (P< 0.05) increase in follistatin release. In contrast, the amount of activin released by the increased dose of LPS was similar to that invoked by the lower dose. The effect of tolerance to LPS was investigated by giving a second challenge of LPS 5 days after the initial injection. In all animals studied, there was an ablated (P < 0.05) response to the subsequent LPS injection, apart from a similar temperature-response profile. These data provide further evidence that activin A concentrations in the bloodstream are acutely responsive to inflammatory challenge in post-natal life and suggest that the response forms a significant component of the innate immune system.

In several biological systems, the inhibin β_A homodimer activin A is stimulated by, and in turn, inhibits the action of interleukin (IL)-1 (both IL-1α and IL-1β) and IL-6. The possibility that a similar regulatory relationship operates within the testis was investigated. Sertoli cells from immature (20-day-old) rats were cultured with human IL-1α or IL-1β, human IL-6 and/or ovine FSH or dibutyryl cAMP. Activin A and the inhibin dimers, inhibin A and inhibin B, were measured by specific ELISA. Immunoreactive inhibin (ir-inhibin) was measured by RIA. Activin/inhibin subunit mRNA expression was measured by quantitative real-time PCR. Both IL-1 isoforms, but not IL-6, stimulated activin A secretion through increased synthesis of β_A-subunit mRNA. IL-1 also stimulated activin A secretion by testicular peritubular cells. In contrast to the effect on activin A, IL-1 suppressed inhibin β_B-subunit and, to a lesser extent, α-subunit mRNA expression, thereby reducing basal and FSH-stimulated inhibin B secretion by the Sertoli cells. Conversely, FSH inhibited basal activin A secretion and antagonised the stimulatory effects of IL-1. Dibutyryl cAMP partially inhibited the action of IL-1 on activin A secretion, but had no significant effect on basal activin A secretion. Secretion of inhibin A was low in all treatment groups. These data demonstrate that IL-1 and FSH/cAMP exert a reciprocal regulation of activin A and inhibin B synthesis and release by the Sertoli cell, and suggest a role for activin A as a potential feedback regulator of IL-1 and IL-6 activity in the testis during normal spermatogenesis and in inflammation.