Ethanol, growth hormone and testosterone in peripubertal rats.

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 Turkey'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.

Coupled reverse transcription-polymerase chain reaction (RT-PCR) technique is comparative, quantitative, and rapid: uses in alcohol research involving low abundance mRNA species such as hypothalamic LHRH and GRF.

The measurement of alterations in low abundance mRNAs such as the hypothalamic hormones luteinizing hormone-releasing hormone (LHRH) and growth hormone-releasing hormone (GHRH or GRF) from individual hypothalamic tissues in rats has previously been difficult and usually required either isolation of poly(A) mRNA or the pooling of numerous animals to obtain a reasonable signal on Northern blots. Although more sensitive detection methods exist, such as the use of RNA probes or solution hybridization (RNase protection), we have found the most reliable, sensitive, rapid, and accurate method is the reverse transcription-polymerase chain reaction (RT-PCR) using histone H3.3 as an internal control for both steps of this procedure. H3.3 is a cell-cycle independent and constitutively expressed gene in all tissues. We have developed an RT-PCR assay for LHRH and GRF mRNA quantitation and comparative analysis for hypothalamic and extrahypothalamic brain tissues and present the use of RT-PCR for LHRH quantitation in ethanol (EtOH) studies.

The effect of acute in vivo ethanol exposure on follicle stimulating hormone transcription and translation.

The impact of ethanol (EtOH) on male rodent reproduction has been well characterized for luteinizing hormone (LH) with suppression of LH release from the pituitary being reported. We have previously reported that acute ethanol (EtOH) exposure in vivo results in rapid and marked suppression of beta-LH gene expression and protein release from the pituitary. This suppression of beta-LH gene expression was unaccompanied by a change in the common alpha-subunit mRNA. To further explore the impact of ethanol on male rodent reproduction, we have expanded our studies to follicle stimulating hormone (FSH) and hypothalamic luteinizing hormone releasing hormone (LHRH) as well as of pituitary protein kinase C (PKC). Previously castrated male rats were acutely exposed to EtOH and a dramatic reduction in both serum FSH and LH levels was noted at 1.5 and 3 hr after treatment. These levels returned to saline injected control values at 6 and 24 hr. Despite the fall in serum FSH, there was no change in intrapituitary FSH content at any time point; this lack of pituitary FSH depletion in the face of a fall in serum levels is suggestive of impaired FSH release. In contrast to the fall in beta-LH steady-state mRNA levels seen previously and confirmed in the present studies, there was no change in beta-FSH steady-state mRNA at any time point suggesting that EtOH has dichotomous effects on the expression of these two gonadotropins. Pituitary PKC levels were also assessed and found to be unaffected by EtOH at any time point.(ABSTRACT TRUNCATED AT 250 WORDS)

The rat prolactin gene is expressed in brain tissue: detection of normal and alternatively spliced prolactin messenger RNA.

Previous work by our laboratory has described the presence and widespread distribution of a PRL-like immunoreactive protein in brain. The persistence of this PRL in brain after hypophysectomy provided substantial evidence that brain PRL represented the product of a synthetic pool separate from that of the anterior pituitary PRL. To pursue this concept of independent synthesis further, we sought to determine whether brain tissue expressed PRL mRNA. Although we were easily able to detect a single species of PRL mRNA in pituitary by Northern hybridization, we could not visualize message in hypothalamus or extrahypothalamic brain by this technique. Therefore, we performed the polymerase chain reaction on cDNAs from anterior pituitary, hypothalamus, discrete extrahypothalamic brain regions, and other tissues. Hypothalamus and extrahypothalamic brain parts, including the cerebellum, caudate, brain stem, amygdala, thalamus, cortex, and hippocampus, were all positive to varying degrees. Lung and liver were negative, and anterior pituitary was consistently positive. All positive tissues, including anterior pituitary, expressed two hybridization signals: the expected amplified product and another smaller one. The smaller amplified product is presumably the result of an alternatively spliced transcript that is missing part of the PRL gene. Hypophysectomized animals did not express PRL message in brain, but expression was restored in hypophysectomized animals treated with testosterone. Transcripts for Pit-1 (GHF-1), a transcription factor important in regulation of pituitary PRL, were not detected in hypothalamus or any of the extrahypothalamic brain parts. The finding of testosterone stimulation of brain PRL message and undetectable levels of Pit-1 (GHF-1) in hypothalamic and extrahypothalamic brain regions indicates that the transcriptional regulation of PRL in the brain is different from that in the anterior pituitary.

Presence of luteinizing hormone-releasing hormone (LHRH) mRNA in rat spleen lymphocytes.

Pursuant to our report of an immunoreactive and bioactive luteinizing hormone-releasing hormone (LHRH)-like molecule in rat spleen lymphocytes, we sought to determine whether these cells were capable of synthesizing LHRH by determining whether lymphocytes contain LHRH mRNA. To do this, total RNA was extracted from hypothalamic tissue, anterior pituitaries and from lymphocytes, and then this was reverse transcribed to cDNA and amplified via the polymerase chain reaction (PCR) utilizing synthetic oligonucleotides bracketing a portion of the LHRH gene. Following gel electrophoresis a discrete band of the expected size of 375 base pairs was found in the hypothalamus (positive control), and in lymphocytes, but not in the anterior pituitary (negative control). Furthermore, after Southern blotting, a 32P-labelled LHRH cDNA, hybridized to the 375 base pair, was amplified in hypothalamus fragments and in lymphocytes, but not in anterior pituitary tissue. These data strongly suggest that LHRH, in addition to being an important neuropeptide, is an immune cell synthesized immunomodulator.

Rat spleen lymphocytes contain an immunoactive and bioactive luteinizing hormone-releasing hormone.

An interaction between the immune and endocrine systems has been long known. This association is further strengthened by the finding that splenic lymphocytes have the capacity to produce molecules similar to if not the same as classical hormones, including several members of the opiate family, PRL, GH, and neuropeptide Y. Because of such findings and because of information from other laboratories suggesting that LHRH might have direct effects upon the immune system, we hypothesized that immune cells themselves might contain LHRH. Lymphocytes were purified from spleens of intact adult male Sprague-Dawley rats and the cells were lysed with sodium hydroxide. The concentration of immunoreactive LHRH was 403 +/- 184 pg/20 X 10(6) lymphocytes. Increasing amounts of lymphocyte lysate displaced [125-I]LHRH from LHRH antibody in a manner parallel to that produced by synthetic hypothalamic LHRH, suggesting immunologic similarity between lymphocyte and hypothalamic LHRH. Lymphocyte LHRH-like immunoactivity coeluted from Nova-Pak C18 columns with synthetic hypothalamic LHRH. When lymphocyte lysates were applied to rat anterior pituitary cells in monolayer culture, significant stimulation of LHRH secretion was seen, from 2,144 +/- 54 pg LH/ml.4 h to 15,364 +/- 587 pg LH/ml.4 h (P less than 0.001), a finding verified in five additional experiments. In other studies, this LH response evoked by lymphocyte lysates was found to be dose dependent and could be significantly inhibited by an LHRH-antagonist. Furthermore, when lymphocyte lysate and identically treated synthetic LHRH were HPLC fractionated, there was coelution of lysate and hypothalamic LHRH bioactivity. The lysate itself contained no substantial LH immunoreactivity. Thus, lymphocytes from spleens of adult male rats contain an immunoactive and bioactive LHRH, a finding further strengthening an association between the endocrine and immune systems.

The effect of in vitro ethanol exposure on LHRH release from perifused rat hypothalami.

A variety of indirect data suggest that the luteinizing hormone (LH) lowering effects of ethanol (ETOH) are mediated at a hypothalamic level decreasing the synthesis and/or release of LH-releasing hormone (LHRH). Little direct data support this concept, however. The current study was, therefore, designed utilizing a perifusion system with frequent sampling for LHRH with and without ethanol added to determine if ethanol had a direct effect on basal or stimulated LHRH release. A variety of secretagogues, including dopamine, norepinephrine, naloxone, prostaglandin E2, and a high dose of potassium were utilized. Ethanol at a dose of 300 mg% did not alter either basal or secretagogue-stimulated LHRH release from the hypothalami of ethanol-naive male rats. Thus, ethanol did not appear to have a direct effect on LHRH in this system. Alterations in LHRH release by ethanol may occur at a suprahypothalamic level, involving neurotransmitter-LHRH interactions. Alternatively, the well-described lowering effect of ethanol on LH may be secondary to a direct pituitary locus of action, or involve a metabolic breakdown product of ethanol rather than ethanol itself.

Cross-reaction of albumin with polyclonal LH antibody on western blots.

When pituitary tissue was subjected to Western blot analysis utilizing polyclonal antibody NIDDK-rLH-S-10, bands at 17 and 19 Kd representing LH subunits were identified. In addition, a high molecular weight 66 Kd band was seen. Surprisingly this high molecular weight band was also seen in rat cerebral cortex, brain stem, hypothalamus, spinal cord, lung, liver, pancreas, spleen, kidney, testis, and serum. Antibody preabsorbed with iodination grade rat LH antigen no longer recognized the 17 and 19 Kd bands in pituitary, but recognized the 66 Kd bands in pituitary and the other tissues examined. Since 66 Kd is the molecular weight of albumin, we found that antisera to rat albumin recognized this same high molecular weight band in the tissues examined. Preabsorption of LH antibody with albumin reduced the ability of that antibody to recognize this 66 Kd. A monoclonal antibody to bovine LH beta-subunit recognized only the LH protein in anterior pituitary, but no high molecular weight band in either pituitary or the other tissues studied. Finally, 10, 100, and 1000 micrograms of rat albumin caused no substantial interference under conditions of RIA. We conclude that the polyclonal antibody, provided by the NIH, is excellent for conditions of RIA, but caution must be exercised when it is used for Western analysis where some lots of this antibody may recognize other unrelated proteins.

Failure of in vitro ethanol to inhibit LHRH release from the hypothalamus.

The reproductive alterations induced by ethanol (ETOH) in the male rodent have been intensively investigated. Although gonadal effects are well characterized, the impact of ETOH on the hypothalamic peptide luteinizing hormone-releasing hormone (LHRH) has been less well defined. The releasability of hypothalamic LHRH in the presence of ETOH has not been directly studied. We report here that ETOH in concentrations of 50 mg% to 400 mg% failed to inhibit LHRH release in vitro.

Anatomical and functional effects of estrogen-induced prolactinomas on the rat hypothalamus.

Although estrogen-induced prolactinomas have been widely studied, little attention has been accorded to local pressure effects of the tumor on the hypothalamus and portal vasculature. To portray the magnitude of this phenomenon, four groups of 12-13-week-old female Fisher 344 rats were studied. Group 1 was an intact control receiving a subcutaneously (SC) placed placebo pellet; group 2 was an ovariectomized control with a SC placed placebo pellet; group 3 was ovariectomized with a 10 mg SC placed diethylstilbestrol (DES) pellet; and group 4 was ovariectomized receiving both 10 mg DES and 10 mg SC placed bromocriptine pellets. Blood samples were obtained at 4 weeks, and the animals were sacrificed at 8 weeks after pellet implantation at which time blood, pituitary and hypothalami were obtained. At 4 weeks serum prolactin levels were similarly and significantly elevated above the control groups in both the DES and DES/bromocriptine groups. By 8 weeks, however, serum prolactin level(s) in the DES-treated animals had tripled from the 4-week value, while levels in the DES/bromocriptine-treated animals were unchanged from the 4-week values. This finding matched the observation that the DES-treated animals had pituitaries 2.5-fold heavier than the DES/bromocriptine animals. The gross and histologic structure of the hypothalami and portal vessels were markedly disrupted in DES-treated rats and much less so in the DES/bromocriptine-treated group. These findings lead us to speculate that the pathogenesis of DES-induced prolactinomas proceeds in two phases: First, there is an early chemical induction phase in which estrogen directly and indirectly stimulates lactotrope proliferation and, second, a mechanical disinhibition phase, where tumor-induced destruction of the hypothalamus and portal vessels unleashes the pituitary from the dopaminergic restraining effects of the hypothalamus.

Hypothalamic prolactin: characterization by radioimmunoassay and bioassay and response to hypophysectomy and restraint stress.

Prompted by immunohistochemical reports of prolactin-like immunoreactivity in cell bodies within the rat hypothalamus, a study was undertaken to quantitate the immunologic and biologic activity of this material. Hypothalamic concentrations of prolactin-like immunoreactivity averaged 402 +/- 23 pg/mg of protein (n = 30). 97% recovery of rat prolactin standards added to homogenates of hypothalamus insured that neuronal tissue, as prepared for these studies, did not interfere with the radioimmunoassay of rat prolactin. Examination of the elution profile from Sephadex G-75 columns of the prolactin-like immunoreactivity in hypothalamic extracts showed that the majority of hypothalamic prolactin-like substance was of a larger molecular size than pituitary prolactin. While increasing amounts of brain extract progressively displaced more I125 prolactin from antibody-binding sites, the displacement curve produced by adding hypothalamic extract was not parallel to that produced by the addition of increasing amounts of anterior pituitary prolactin standards of rat origin. Hypothalamic extracts from hypophysectomized animals, analyzed for biologic activity in the Nb2 lymphoma cell assay, revealed prolactin-like bioactivity, but the bioactivity/immunoactivity (B/I) ratios for hypothalamic extracts were significantly lower than the B/I ratios for pituitary prolactin (0.71 +/- 0.04 for pituitary, vs. 0.19 +/- 0.06 in the hypothalamus; p less than 0.001). Hypophysectomy, which led to the expected fall in serum prolactin to undetectable levels, and restraint stress, which resulted in a statistically significant 4-fold rise in serum prolactin, caused no change in prolactin concentrations in the hypothalamus, indicating that brain prolactin-like substance is regulated independently of pituitary prolactin and circulating serum prolactin levels.