Abstract

Ethanol (EtOH) has previously been shown to have profound effects on various endocrine systems. The present study further investigates the action of EtOH on testosterone and on the GH–IGF-I axis. Since these hormones are particularly important in male rats progressing through puberty, we examined the effect of 10 days of EtOH treatment at three different ages (35, 50 and 65 days old) as male rats progressed through puberty into adulthood. After 10 days of feeding a 6% EtOH liquid diet, serum testosterone levels were markedly decreased in all three ages (P<0·02 at 35 days, P<0·01 at 50 days and P<0·03 at 65 days). IGF-I was assessed and was differentially affected at each age. At 35 days IGF-I levels were suppressed by EtOH (P<0·0002), at 50 days no change was apparent, and at 65 days levels were significantly higher in EtOH-treated (P<0·01) compared with liquid-fed controls. The levels of IGF-I in the EtOH-treated animals paralleled pituitary GH mRNA levels with a significant fall in the expression of GH mRNA levels noted at 35 days (P<0·04), no change at 50 days and a significant rise observed at 65 days (P<0·03). At the hypothalamic level, GH-releasing hormone (GRF) mRNA was significantly reduced in the two younger EtOH-treated age groups compared with controls (P<0·04 at 35 days; P<0·02 at 50 days). At 65 days of age, EtOH did not alter GRF mRNA levels. No EtOH-induced changes were seen in GRF content at any age. These observations indicate definite age-related alterations in hormonal gene expression and circulating serum hormone levels and emphasize the importance of studying these critical peripubertal ages after chronic EtOH exposure.

Journal of Endocrinology (1997) 154, 363–370

ABSTRACT

Alphaxalone is considered the anaesthetic of choice in neuroendocrine reproductive studies in female rats, since it appears to have little, if any, effect on release of gonadotrophin-releasing hormone. There has been less study of the effects of this anaesthetic on the male reproductive neuroendocrine axis, however. Accordingly, the time-dependent effects of alphaxalone, as well as of urethane and ketamine, on the increased levels of LH in castrated rats were determined. Each anaesthetic was administered i.p. and each depressed LH levels significantly compared with those in castrated unanaesthetized rats killed by decapitation (controls). The effect of the anaesthetics was noted 15 min after administration and persisted at 30 and 60 min in animals anaesthetized with alphaxalone and urethane. Only in ketamine-anaesthetized animals did serum concentrations of LH finally rise to concentrations not significantly different from those in control rats. Thus alphaxalone, though useful in female neuroendocrine studies, is as profoundly disruptive as other anaesthetics on the male rat hypothalamic-pituitary reproductive unit.

J. Endocr. (1987) 115, 221–223

ABSTRACT

The effect of exposure to ethanol on hypothalamic LH-releasing hormone (LHRH) release in vivo was investigated in rats both acutely (i.p. injection) and after 3 days of administration, utilizing a permanent gastric cannula. In both designs, the animals were castrated before being given ethanol and, in both experiments, ethanol successfully lowered the post-castration LH rise compared with control castrated animals. In both the acutely and chronically treated groups, basal LHRH release was not impaired, despite the documented decrease in LH levels. Finally, stimulated LHRH release was investigated with depolarizing concentrations of potassium and, again, no change was noted between the hypothalamic release of this decapeptide in the ethanol-exposed compared with the ethanol-naive animals. Thus, ethanol failed to inhibit basal or stimulated LHRH secretion in the acutely and chronically treated animal. This lack of effect on LHRH occurred despite a concomitant lowering of serum concentrations of LH.

Journal of Endocrinology (1989) 121, 37–41

Abstract

Many studies have consistently shown that castration induces a prompt increase in serum levels and pituitary content of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as a concomitant rise in steady state levels of the messenger RNAs directing their synthesis. The reports of effects of castration on the overall physiology of hypothalamic luteinizing hormone-releasing hormone (LHRH) — steady state levels of LHRH mRNA, post-translational processing and secretion — have, however, not been consistent.

The goal of the studies reported here was to provide the first analysis of the effect of castration, at multiple post-operative time points, on steady state levels of LHRH mRNA and on the levels of hypothalamic proLHRH. All these data are correlated with hypothalamic levels of the mature LHRH decapeptide and with serum and pituitary levels of immunoreactive LH and FSH.

Adult male rats were either castrated or sham-castrated (controls) and then sacrificed at 1, 3, 5, 7, 14, 21 or 28 days postoperatively. As expected, there was a prompt and sustained rise in serum immunoreactive LH and FSH in castrates compared with sham-operated animals. Intrapituitary LH levels rose above levels in the sham-operated animals by 14 days post castration. Intra-pituitary FSH showed a biphasic response, first falling significantly below control levels, then rising above control levels at 21 days.

Steady state levels of LHRH mRNA in castrates, measured by reverse transcription/polymerase chain reaction, were increased about 2-fold above control levels by 1 day postoperatively, but were virtually identical to control levels at each of the other time points despite marked changes in the gonadotropins.

ProLHRH content in castrates was 1·8-times that seen in controls at 1 day post castration (P<0·05), concomitant with the rise in steady state levels of LHRH mRNA at that time point. However, proLHRH content in castrates was no different from that seen in controls at each of the later time points examined. LHRH content was unchanged through 7 days after castration, but then fell significantly to 57% of control levels in hypothalami from animals gonadectomized 14 to 21 days previously (P<0·001 vs control), and to 54% of sham-operated levels at 28 days postoperatively (P<0·001).

We conclude that: (1) changes in steady state levels of LHRH mRNA after castration are small and transient and (2) increased proLHRH coupled with unchanged LHRH levels at 1 day post castration, and castrate animal pro-LHRH at control levels coupled with falling LHRH at later post-castration time points indicate that the effect of gonadectomy on post-translational processing of pro-LHRH to LHRH is, likewise, small and transient.

In aggregate our data suggest that most of the increase in serum LH and FSH seen in male rats after castration is not mediated at the hypothalamic level.

Journal of Endocrinology (1996) 148, 509–515

The deleterious effects of ethanol on the hypothalamic pituitary growth hormone axis in adult male humans and animals have been well documented. It is also well established that ethanol has toxic effects on testicular function in adult humans and animals. Much less is known, however, about the effects of ethanol on the growth hormone (GH) axis and testicular function in adolescence. Recent studies have established that adolescent problem drinking is a widespread and growing threat to the health of young people in the United States. In the present study, therefore, we investigated if acute ethanol exposure in peripubertal male Sprague–Dawley rats altered normal pituitary and testicular function.

Serum levels of GH and testosterone were measured at 1·5, 3, 6, and 24 h after a single i.p. injection of either saline or 3 g/kg body weight ethanol. Histologic analysis as well as serum testosterone levels allowed us to assign animals to either early puberty (35-day-old animals), mid-puberty (41-day-old animals), or young adult (51- and 66-day-old animals) status. Ethanol produced significant decrements in serum testosterone in the 51-and 66-day-old animals, with a trend toward suppression in the 41-day-old group. Furthermore acute ethanol administration significantly decreased serum GH (P< 0·0001 by 3 way ANOVA) demonstrating a significant effect of ethanol on serum GH in all age groups and at all time points studied when compared with saline injected controls (P<0·01 by Tukey's studentized range test). Despite this significant fall in peripheral GH levels, there was no decrease in either GH mRNA or growth hormone-releasing factor (GRF) mRNA levels nor in hypothalamic concentration of GRF peptide.

We conclude that, as in adult animals, acute exposure to ethanol causes a prolonged and severe decrement in serum GH which is possibly mediated at the level of secretion. In addition, there is attenuation in testosterone secretion. These data are all the more important since GH and testosterone play critical roles in organ maturation during this stage of development.

Journal of Endocrinology (1997) 152, 477–487

Abstract

Jurkat cells were used to study the immunomodulatory role of luteinizing hormone-releasing hormone (LHRH) in immune cells. The Jurkat cell, a human mature leukemic cell line, phenotypically resembles resting human T lymphocytes and has been widely used to study T cell physiology. The data from this study demonstrate that the Jurkat cell concentration of immunoreactive LHRH was 210 ± 36 pg/10⁶ cells and that of proLHRH was 188 ± 27 pg/10⁶ cells (means ± s.e.m.). The authenticity of this LHRH immunoreactivity is documented in two ways. First, both Jurkat LHRH and proLHRH immunoreactivity demonstrate dilutional parallelism with hypothalamic LHRH and proLHRH. Second, Jurkat lysates show LHRH bioactivity by releasing luteinizing hormone from rat anterior pituitary cells in culture. The presence of substantial amounts of LHRH in medium in which Jurkat cells were cultured for 72 h indicated that LHRH can be released from the cells. Using specific primers to exons 2 and 4 of the LHRH gene, we have found that Jurkat cells (like human T cells) express LHRH mRNA.

The LHRH agonist, des-Gly¹⁰,d-Trp⁶-LHRH ethylamide, significantly increases the proliferative activity of Jurkat cells, as assessed by tritiated thymidine incorporation, from 15 980 ± 1491 c.p.m. in controls to 28 934 ± 3395, 30 457 ± 3861 (P=0·05 vs control) or 35 299 ± 5586 c.p.m. (P<0·01 vs control) with 10⁻¹¹, 10⁻⁹ or 10⁻⁷ m agonist respectively. LHRH antagonist, [d-pGlu¹,d-Phe²,d-Trp^3,6]-LHRH, at a concentration of 10⁻⁸ m decreases Jurkat cell proliferative activity from 17 145 ± 526 c.p.m. in control medium to 10 653 ± 1323 c.p.m. (P=0·05). Co-incubation with the LHRH antagonist completely inhibits the proliferative stimulation induced by the LHRH agonist. Furthermore, applying monoclonal LHRH antibody to Jurkat cells inhibits the cell proliferative activity assessed by tritiated thymidine incorporation from 19 900 ± 2675 c.p.m. in controls to 15 680 ± 2254, 15 792 ± 1854 and 9700 ± 908 c.p.m. in media with 1:40, 1:20 and 1:10 dilution of purified antibody respectively (P<0·01, 1:10 dilution compared with control). In addition, the cAMP level in LHRH-stimulated Jurkat cells is decreased to 74, 27 and 57% of control levels after 15, 30 and 45 min respectively of exposure to 10⁻⁷ m LHRH agonist.

In summary, Jurkat cells produce, process and release immunoreactive and bioactive LHRH, as do normal human T cells. Endogenous and exogenous LHRH increase Jurkat cell proliferative activity, and cAMP may be involved in LHRH-induced Jurkat cell proliferation. The Jurkat cell may be a useful model with which to study the role of LHRH in human T cell function.

Journal of Endocrinology (1997) 153, 241–24