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

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

The TALLYHO/JngJ (TH) strain is a newly established, polygenic mouse model for type 2 diabetes (T2D) and obesity, and we have previously reported some key physiological features of this model after the overt onset of diabetes. In the present work, we conducted a comprehensive phenotypic characterization of TH in order to completely characterize this new and relevant model for human T2D and obesity. We monitored the development of obesity and diabetes starting at 4 weeks of age by measuring body weight, glucose tolerance, and plasma levels of insulin, glucose, and triglyceride. Additionally, histological alterations in the pancreas and glucose uptake and glucose transporter 4 (GLUT4) content in soleus muscle were also examined. Compared with age- and sex-matched C57BL/6J (B6) mice, both male and female TH mice were significantly heavier, hyperleptinemic, and hyperinsulinemic at 4 weeks of age, without glucose intolerance or hyperglycemia. TH mice maintained higher body weights throughout the study period of 16 weeks. The hyperinsulinemia in TH mice worsened with age, but to a lesser degree in females than in males. Both the male and the female TH mice had enlarged pancreatic islets. Male TH mice showed impaired glucose tolerance at 8 weeks that became more prominent at 16 weeks. Plasma glucose levels continuously increased with age in male TH mice resulting in frank diabetes, while female TH mice remained normoglycemic throughout the study. Impaired glucose tolerance and hyperglycemia in male TH mice were accompanied by impaired 2-deoxyglucose uptake in the soleus muscle at basal and insulin-stimulated states, but without any reduction in GLUT4 content. Interestingly, male TH mice exhibited a drastic elevation in plasma triglyceride levels in the pre-diabetic stage that was maintained throughout the study. These findings suggest that obesity and insulin resistance are an inherent part of the TH phenotype and glucose intolerance is evident preceding progression to overt diabetes in male TH mice.