Recurrence of hyperprolactinemia after withdrawal of long-term cabergoline therapy

CONTEXT

Recurrence of hyperprolactinemia after cabergoline withdrawal ranges widely from 36 to 80%. The Pituitary Society recommends withdrawal of cabergoline in selected patients.

OBJECTIVE

Our aim was to evaluate recurrence of hyperprolactinemia in patients meeting The Pituitary Society guidelines.

DESIGN

Patients were followed from the date of discontinuation to either relapse of hyperprolactinemia or the day of last prolactin test.

SETTING

We conducted the study at an academic medical center.

PATIENTS

Forty-six patients meeting Pituitary Society criteria (normoprolactinemic and with tumor volume reduction after 2 or more years of treatment) participated in the study.

INTERVENTIONS

After withdrawal, if prolactin returned above reference range, another measurement was obtained within 1 month, symptoms were assessed by questionnaire, and magnetic resonance imaging was performed.

MAIN OUTCOME MEASURES

We measured risk of and time to recurrence estimates as well as clinical predictors of recurrence.

RESULTS

Mean age of patients was 50 +/- 13 yr, and 70% were women. Thirty-one patients had microprolactinomas, 11 had macroprolactinomas, and four had nontumoral hyperprolactinemia. The overall recurrence was 54%, and the estimated risk of recurrence by 18 months was 63%. The median time to recurrence was 3 months (range, 1-18 months), with 91% of recurrences occurring within 1 yr after discontinuation. Size of tumor remnant prior to withdrawal predicted recurrence [18% increase in risk for each millimeter (95% confidence interval, 3-35; P = 0.017)]. None of the tumors enlarged in the patients experiencing recurrence, and 28% had symptoms of hypogonadism.

CONCLUSIONS

Cabergoline withdrawal is practical and safe in a subset of patients as defined by The Pituitary Society guidelines; however, the average risk of long-term recurrence in our study was over 60%. Close follow-up remains important, especially within the first year.

GABRA6 gene polymorphism and an attenuated stress response

The glucocorticoid component of the stress response has been the subject of intense scientific scrutiny because of the wide ranging pathological consequences resulting from excess glucocorticoid exposure, including mood and anxiety disorders, and cognitive impairment. Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic adrenomedullary system, which are regulated by neuronal pathways, including the inhibitory GABAergic (gamma-aminobutyric acid) system. Approximately 60% of the variance in glucocorticod levels may be attributable to genetic individual differences. In the present study, 56 healthy subjects underwent genotyping to determine the influence of the T1521C single nucleotide polymorphism (SNP) in the GABA(A)alpha6 receptor subunit gene (GABRA6) on the hormonal and autonomic responses to psychological stress induced by the Trier Social Stress Test (TSST). Adrenocorticotropin (ACTH), cortisol, diastolic blood pressure, and mean blood pressure responses to the TSST were significantly greater in subjects homozygous for the T allele or heterozygous compared to subjects homozygous for the C allele. Behavioral data was collected employing the Revised NEO Personality Inventory (NEO PI-R); subjects homozygous for the C allele scored significantly lower on the Extraversion factor compared to subjects homozygous for the T allele or heterozygous. These results suggest that the T1521C polymorphism in the GABRA6 gene is associated with specific personality characteristics as well as a marked attenuation in hormonal and blood pressure responses to psychological stress.

Opioids and alcoholism

Although far from conclusive, evidence implicating the endogenous opioid system in the development and maintenance of alcoholism is growing. Currently available data suggest that ethanol increases opioid neurotransmission and that this activation is part of the mechanism responsible for its reinforcing effects. Findings from preclinical research indicate that ethanol consumption and ethanol-induced dopamine (DA) release are both reduced by opioid antagonists. Individual differences in endogenous opioid activity have been linked to inherited risks for alcoholism in studies comparing ethanol-preferring and nonpreferring rats, as well as in studies using targeted gene mutation (knockout) strategies. To a large extent, findings from human studies have paralleled those from the preclinical work. Persons who differ in family history of alcoholism have been shown to also differ in basal beta-endorphin activity, beta-endorphin response to alcohol, and subjective and HPA axis hormonal response to opioid antagonists. Findings from clinical trials indicate that opioid antagonists may reduce ethanol consumption in alcoholics, particularly in persons who have resumed drinking. Nevertheless, many questions remain unanswered about the use of opioid antagonists in alcoholism treatment and about the exact role of the opioid system in ethanol preference and reward. The progression of knowledge in this field suggests that many of these questions are imminently answerable, as our ability to characterize relationships between opioid activity and human behavior continues to develop. This paper summarizes both the progress that has been made and the gaps that remain in our understanding of the interactions between the endogenous opioid system and risk for alcoholism.

Naltrexone dampens ethanol-induced cardiovascular and hypothalamic- pituitary-adrenal axis activation

Alcohol ingestion activates the autonomic nervous system and the hypothalamic-pituitary-adrenal axis. This study examined naltrexone effects on alcohol-induced increases in physiological responses and their association with alcohol liking. Using a within-subjects design, heavy drinking men (N = 19) were maintained on each of three naltrexone doses (0, 50, and 100 mg, p.o.) over an 8-day inpatient stay. Within each naltrexone dose, subjects had three alcohol challenge sessions (none, moderate, high) in random order. Autonomic, subjective and endocrine measurements were collected regularly prior to and following alcohol administration. High-dose alcohol ingestion increased heart rate, diastolic blood pressure, skin temperature, ACTH, cortisol and liking of drink effects; responses following the moderate alcohol dose were less consistent. Naltrexone significantly dampened alcohol-induced increases in heart rate, diastolic blood pressure, hormone levels and subjective liking of drink effects. This dampening of cardiovascular and hormonal responses may contribute to the therapeutic effectiveness of naltrexone for reducing alcohol liking and decreasing relapse in alcohol-dependent persons.

Association of IGF-I levels with muscle strength and mobility in older women

The functional consequences of the age-associated decline in IGF-I are unknown. We hypothesized that low IGF-I levels in older women would be associated with poor muscle strength and mobility. We assessed this question in a population representative of the full spectrum of health in the community, obtaining serum IGF-I levels from women aged 70-79 yr, enrolled in the Women's Health and Aging Study I or II. Cross-sectional analyses were performed using 617 women with IGF-I levels drawn within 90 d of measurement of outcomes. After adjustment for age, there was an association between IGF-I and knee extensor strength (P = 0.004), but not anthropometry or other strength measures. We found a positive relationship between IGF-I levels and walking speed for IGF-I levels below 50 microg/liter (P < 0.001), but no relationship above this threshold. A decline in IGF-I level was associated with self-reported difficulty in mobility tasks. All findings were attenuated after multivariate adjustment. In summary, in a study population including frail and healthy older women, low IGF-I levels were associated with poor knee extensor muscle strength, slow walking speed, and self-reported difficulty with mobility tasks. These findings suggest a role for IGF-I in disability as well as a potential target population for interventions to raise IGF-I levels.

Serum 6-beta-naltrexol levels are related to alcohol responses in heavy drinkers

BACKGROUND

There is strong evidence for the role of the endogenous opioid system in alcohol reinforcement and consumption; however, recent human laboratory studies and clinical trials have reported mixed effects of naltrexone (a nonselective opioid antagonist) on alcohol-related behaviors. This paper reports a secondary data analysis of a human laboratory study that examines the relationship between serum levels of 6-beta-naltrexol, the major, biologically active metabolite of naltrexone, and subjective effects of alcohol.

METHODS

The study used a within-subjects design to examine the effects of naltrexone (0, 50, and 100 mg/day) on subjective responses to alcohol (none, moderate, and high dose) in heavy drinkers (n = 23). Each subject received three doses of naltrexone in random order; each naltrexone dose was administered over an 8 day period on an inpatient unit, with a 1 week outpatient washout between doses. After stabilization at each of the naltrexone doses, subjects participated in three alcohol challenge sessions (none, moderate, and high dose) in random order; thus, each subject participated in a total of nine alcohol administration sessions.

RESULTS

Doubling the naltrexone dose (50 vs. 100 mg/day) doubled the mean serum 6-beta-naltrexol levels. At each naltrexone dose, there was a 4-fold range in 6-beta-naltrexol levels across subjects. Before alcohol administration, higher 6-beta-naltrexol levels were associated with higher ratings of sedation. After high-dose alcohol administration, higher 6-beta-naltrexol levels were associated with significantly lower ratings of liking and best effects.

CONCLUSIONS

These findings provide further evidence of the involvement of the opioid system in the modulation of alcohol effects and suggest that serum 6-beta-naltrexol concentrations may be important in predicting therapeutic response to naltrexone.

Plasma adrenocorticotropin responses to opioid blockade with naloxone: generating a dose-response curve in a single session

We examined two methods of generating a dose-response curve to the opioid receptor antagonist naloxone. In 15 healthy male subjects (18-25 years) plasma adrenocorticotropin (ACTH) responses to five doses of naloxone studied over 5 separate days were compared to plasma ACTH responses to five incremental doses of naloxone studied within a single session. There was a statistically significant positive correlation in ACTH responses (area under the curve and peak) between dosing methods. Furthermore, the doses of naloxone that produced half-maximal and maximal ACTH response were similar. The comparability of ACTH responses between the two naloxone dosing techniques, combined with the safety and ease associated with the single-session methodology, underscores the usefulness of the single-session technique for future investigations.

Corticotropin-independent Cushing's syndrome caused by an ectopic adrenal adenoma

Although nonsecreting suprarenal embryonic remnants are frequently found in the urogenital tract, adenomatous transformation resulting in glucocorticoid excess is a rare phenomenon. We report a case of a 63-yr-old woman that presented with new-onset hirsutism, facial plethora, hypertension, centripetal obesity, and a proximal myopathy. The 24-h urinary free cortisol excretion rate was elevated, and the serum ACTH level was suppressed. The patient failed an overnight and low dose dexamethasone suppression test and did not respond to CRH stimulation. In light of the undetectable baseline morning ACTH levels and the blunt response to CRH, the diagnosis of corticotropin-independent Cushing's syndrome was made. Imaging studies revealed normal adrenal glands and enlargement of a left pararenal nodule incidentally observed 4 yr before the onset of symptoms. Dramatic resolution of symptoms was observed after surgical removal of the 3.5-cm mass. Pathological exam confirmed adrenocortical adenoma in ectopic adrenal tissue. The case reported here represents the unusual circumstance in which the development of adenomatous transformation of ectopic adrenal tissue has been prospectively observed with imaging studies. It illustrates the importance of considering ectopic corticosteroid-secreting tumors in the context of corticotropin-independent Cushing's syndrome.

Endogenous opioid activity is associated with obsessive-compulsive symptomology in individuals with a family history of alcoholism

Endogenous opioid activity has been associated with the regulation of mood and inhibition of the hypothalamic-pituitary-adrenal (HPA) axis. We assessed differences in psychological symptomology and naloxone sensitivity in non-alcoholic males and females with a family history of alcoholism (FHP) and without a family history of alcoholism (FHN). This was followed by assessment of the association between naloxone sensitivity and psychological symptomology. Psychological symptomology was measured using the Revised Symptom Checklist (SCL-90-R) during enrollment. Adrenocorticotropin was measured following intravenous administration of naloxone/placebo. FHP males reported more obsessive-compulsive symptomology as well as increased sensitivity to naloxone relative to other groups. A positive association was observed between degree of obsessive-compulsive symptomology and naloxone sensitivity, and the association was strongest among FHP males. These findings suggest that the increased risk of alcoholism in FHP subjects (especially males) may be associated with altered opioid activity, which is expressed through an elevated level of obsessive compulsive symptomology.

Naltrexone alters subjective and psychomotor responses to alcohol in heavy drinking subjects

Preclinical studies support endogenous opioid system involvement in alcohol reinforcement and consumption; however, recent clinical trials and human laboratory studies have provided mixed findings of the effects of naltrexone (a non-selective opioid antagonist) on alcohol responses. This study used a within-subject design (n = 23) to investigate naltrexone effects (0, 50 and 100 mg qd) on subjective and psychomotor responses to alcohol (none, moderate, high) in heavy drinkers. Before alcohol administration, subjects reported decreased desire to drink alcohol when maintained on 50 mg compared with placebo naltrexone. Following alcohol administration, active naltrexone significantly increased subjective ratings of sedative, and unpleasant/sick effects and decreased ratings of liking, best effects and desire to drink. Naltrexone generally did not alter subjective or objective indicators of drunkenness. Finally, high doses of naltrexone and alcohol interacted to produce the greatest decreases in liking and best effects. Findings support the role of endogenous opioids as determinants of alcohol's effects and suggest that naltrexone may be particularly clinically useful in those treatment patients who continue to drink heavily.

Adrenocortical responses and family history of alcoholism

BACKGROUND

This study was designed to assess whether nonalcoholic offspring from families with a high density of alcohol-dependent individuals have altered hypothalamic-pituitary-adrenal (HPA) axis dynamics compared with nonalcoholic subjects without a family history of alcohol dependence.

METHODS

Seventy-eight nonalcoholic subjects aged 18 to 25 were enrolled in the protocol. Thirty-nine subjects were offspring from families with a high density of alcohol dependence and were designated as family history-positive (FHP) subjects. Thirty-nine subjects were biological offspring of nonalcohol-dependent parents and were designated as family history-negative (FHN) subjects. Subjects received naloxone hydrochloride (0 and 125 microg/kg) and cosyntropin (0, 0.25 microg, and 250 microg) in double-blind, randomized order and cortisol was monitored. A subset of subjects (11 FHP, 11 FHN) was admitted to the General Clinical Research Center to measure serum cortisol levels every 30 min for 24 hr.

RESULTS

FHP subjects had an increased cortisol response to opioid receptor blockade induced by naloxone. However, no group differences in cortisol were uncovered during administration of cosyntropin or during monitoring of the cortisol circadian profile.

CONCLUSION

These observations suggest that differences in the cortisol dynamics between FHP and FHN subjects are unmasked by opioid receptor blockade directed at the hypothalamus, but not when cortisol levels are directly provoked at the level of the adrenal gland. In addition, unprovoked cortisol secretion monitored over a 24-hr interval cannot distinguish FHP from FHN subjects.

Adrenocorticotropin responses to naloxone in sons of alcohol-dependent men

The endogenous opioid system is part of a neural circuitry functionally related to alcohol-seeking behaviors. A family history of alcoholism is the strongest predictor of future development of alcohol dependence. This study was designed to evaluate ACTH responses to opioid receptor blockade as a function of family history for alcohol dependence. The nonselective opioid antagonist naloxone stimulates ACTH secretion by blocking opioidergic input on paraventricular corticotropin-releasing factor neurons, thereby providing a methodology for comparing hypothalamic opioid tone between study groups. Sixty nonalcoholic subjects, aged 18-25 yr, were enrolled in a protocol to measure the ACTH response to naloxone. Thirty-two subjects were offspring from families with a high density of alcohol dependence and were designated as family history-positive subjects. Twenty-eight subjects were offspring of nonalcohol-dependent parents and were designated family history-negative subjects. Subjects received naloxone (125 microg/kg) or placebo (0.9% saline) in double blind, randomized order. Plasma ACTH was monitored. Family history-positive men had increased ACTH response to naloxone compared to 1) family history-positive women, 2) family history-negative men, and 3) family history-negative women. Despite differences in plasma ACTH levels after naloxone administration, plasma naloxone concentrations did not differ between study groups. This finding suggests that nonalcoholic male offspring of alcohol-dependent men have altered endogenous opioid activity directed at hypothalamic corticotropin-releasing factor neurons.

Family history of alcoholism and hypothalamic opioidergic activity

BACKGROUND

This study was designed to assess whether nonalcoholic offspring from families with a high density of alcohol-dependent individuals have altered endogenous central nervous system opioid activity. Naloxone hydrochloride stimulates plasma cortisol by blocking opioidergic input on the corticotropin-releasing factor neuron, thereby providing a noninvasive method for measuring hypothalamic opioid tone.

METHODS

Forty-eight nonalcoholic subjects aged 18 to 25 years were enrolled in a protocol to measure endogenous opioid activity by inducing opioid receptor blockade with the receptor antagonist, naloxone. Twenty-six subjects were offspring from families with a high density of alcohol dependence and were designated as family history-positive subjects. Twenty-two subjects were biological offspring of nonalcohol-dependent parents and designated as family history-negative subjects. Subjects received naloxone hydrochloride (0, 125, and 375 microg/kg) in double-blind, randomized order. Serum cortisol levels were monitored.

RESULTS

Family history-negative subjects had a graded cortisol response to each dose of naloxone. In contrast, family history-positive subjects achieved a maximal cortisol response to the 125-microg/kg dose of naloxone hydrochloride with no further increase in cortisol levels observed following the 375-microg/kg dose. Family history-negative subjects had a diminished cortisol response to the 125-microg/kg dose compared with the family history-positive subjects. Plasma naloxone concentrations did not differ between family history groups.

CONCLUSIONS

Individuals from families with a high density of alcohol dependence are more sensitive to naloxone compared with offspring of nonalcohol-dependent parents. This implies that individuals with a family history of alcohol dependence have diminished endogenous hypothalamic opioid activity.

Relationship between plasma adrenocorticotropin, hypothalamic opioid tone, and plasma leptin

The purpose of the present study was to further the understanding of the relationship between plasma leptin concentrations, hypothalamic opioid tone, and plasma ACTH secretory dynamics. ACTH(1-24) challenges (250 micrograms) produced the expected increase in plasma cortisol levels but did not alter plasma leptin levels. Activation of the entire hypothalamic-pituitary-adrenal (HPA) axis was induced by employing the opioid receptor antagonist, naloxone. By blocking opioidergic inhibitory input to hypothalamic CRH neurons, naloxone induced the expected increase in plasma ACTH and cortisol. Plasma ACTH levels peaked 30 min after naloxone administration, whereas plasma cortisol levels peaked 60 min after opioid receptor blockade. Once again, plasma leptin concentrations were not altered by this manipulation. However, there was a positive correlation between fasting, integrated plasma leptin concentrations, and plasma ACTH responses to naloxone (peak r = 0.822, P < 0.0001; and area under curve r = 0.832, P < 0.0001). The correlation was stronger when leptin was normalized to body mass index and expressed as the leptin/body mass index ratio (peak r = 0.878, P < 0.00001; and area under curve r = 0.882, P < 0.00001). In summary, these findings indicate that activation of the HPA axis does not acutely alter plasma leptin concentrations. However, plasma leptin levels may influence hypothalamic opioidergic tone and thus modulate the magnitude of CRH release. The acute interaction of the HPA axis and leptin is unidirectional.

Chronic ethanol exposure impairs phosphorylation of CREB and CRE-binding activity in rat striatum

This study examined influences of ethanol exposure on phosphorylation of cAMP response element-binding protein (CREB) and CRE-binding activity in the striatum of rats. The phosphorylated form of CREB increased 180% during acute intoxication, compared to sham conditions. After chronic ethanol exposure, induction of CREB phosphorylation by an acute ethanol challenge was markedly attenuated (50%) compared with acute ethanol exposure in the pair-fed condition. Gel retardation assays with oligomers encoding the rat proenkephalin CRE-1 and CRE-2 were performed to determine the effects of ethanol on CRE-binding activity. Supershift experiments demonstrated that striatal nuclear protein contains CREB and CEBPPbeta (CCAAT/enhancer-binding protein) and that both transcription factors are involved in specifically binding to the DNA sequence. Rechallenging rats that had been chronically exposed to ethanol with an acute ethanol challenge reduced the CRE/nuclear protein complexes. However, supershift analyses did not show that chronic ethanol exposure altered the dimerization patterns of CREB and CEBPbeta within the complexes. Associated with these impairments in CREB binding and CREB phosphorylation was a significant reduction in two CREB-modulated factors, proenkephalin and c-fos expression. In summary, acute ethanol exposure activates the phosphorylation of CREB. Neuroadaptation to chronic ethanol exposure includes alterations in CREB physiology that may impair genes that are dependent upon CREB for transcriptional activation.

Effect of mu opioid receptor blockade on alcohol intake in rats bred for high alcohol drinking

Beta-funaltrexamine (beta-FNA), a selective mu opioid receptor antagonist, when administered in doses of 10.0, 15.0, and 20.0 mg/kg b.wt., decreased alcohol but not water intake in a dose-dependent manner in rats selectively bred for high alcohol intake (HAD line). Beta-FNA also suppressed the intake of a saccharin solution containing alcohol without altering the intake of a similar solution without alcohol. The results suggest that beta-FNA may prove useful as a pharmacotherapeutic agent for the treatment of alcohol dependence. In a second study, pituitary beta-endorphin gene expression (proopiomelanocortin or POMC messenger ribonucleic acid-mRNA) was compared in another pair of rat lines selectively bred for high or low alcohol intake (alcohol-preferring or P and alcohol-nonpreferring or NP lines). A repeated alcohol challenge (1.0 g/kg b.wt./day, IP for 4 days) produced a greater increase in POMC mRNA in the anterior and neurointermediate lobes of the pituitary of P rats compared with NP rats. The results suggest that a genetic predisposition toward high alcohol drinking may be associated with increased responsiveness of the opioid system to alcohol.

Chronic ethanol administration decreases phosphorylation of cyclic AMP response element-binding protein in granule cells of rat cerebellum

To help define the molecular basis of ethanol's actions on the nervous system, we have in previous studies demonstrated that ethanol administration triggers a robust increase in cyclic AMP-response element-binding protein (CREB) phosphorylation in the cerebellum. The purpose of the present study was to compare the effects of acute and chronic ethanol exposure on the phosphorylation of CREB in rat cerebellum and to determine which cell types in the cerebellum display this response to ethanol. An acute ethanol challenge (3.0 g/kg of body weight) induced a rapid increase in content of the phosphorylated form of CREB, peaking at 30 min and declining to basal levels within 2 h. Immunocytochemical studies revealed prominent ethanol-induced changes in phosphoCREB in the granule cell layer, with little phosphoCREB apparent in Purkinje cells. Following chronic ethanol exposure (5 weeks), induction of CREB phosphorylation by a subsequent acute ethanol challenge was markedly attenuated. The attenuation in CREB phosphorylation was associated with a significant reduction in the levels of the catalytic unit of protein kinase A and calcium/calmodulin-dependent protein kinase IV. In summary, induction of CREB phosphorylation in cerebellum is most prominent in the granule cell layer. Neuroadaptation to chronic ethanol exposure includes a reduction in nuclear protein kinase A and calcium/calmodulin-dependent protein kinase IV levels, an event associated with impaired CREB phosphorylation.

Adenylyl cyclase signal transduction and alcohol-induced sedation

This study examined adenylyl cyclase (AC) signal transduction in alcohol-sensitive brain regions of rats selectively bred for high (HAD) and low (LAD) alcohol drinking and correlated these findings with differences in sensitivity and tolerance to alcohol-induced sedation found within these lines. LAD rats were more sensitive to the sedative effects of alcohol than were HAD rats as evidenced by a shorter latency to lose the righting response (RR) after a single alcohol challenge. When time to recover the RR was compared after each of two alcohol challenges, HAD rats recovered the RR more rapidly following the second challenge compared to the first, indicating that the HAD rats rapidly developed tolerance to the sedative effects of alcohol. Tolerance did not develop in rats of the LAD line. Two months after completion of behavioral testing, adenylyl cyclase (AC) signal transduction was examined in alcohol-sensitive brain regions of rats from both lines. Immunoblot analyses indicated that LAD rats had greater Gs alpha expression in the frontal cortex (FC) and hippocampus (HIP) compared to HAD rats. Rats with the highest HIP and FC Gs alpha levels were more rapidly affected by the sedative properties of alcohol than were rats with lower Gs alpha levels. G protein expression and AC activity in the FC, HIP, cerebellum (CERE), and nucleus accumbens (ACB) were also correlated with sensitivity to the sedative properties of alcohol and with the rapid development of tolerance to this alcohol effect. The results suggest that sensitivity and tolerance to alcohol-induced sedation may be mediated in part through AC signal transduction.

Increased expression of Gs(alpha) enhances activation of the adenylyl cyclase signal transduction cascade

Expression of the stimulatory G protein, G(S)alpha, can vary over a 3-fold range in human tissues and in rodent central nervous system. In fact, the offspring of alcoholics have higher levels of G(S)alpha expression in certain tissues compared with the offspring of nonalcoholics. The aim of this research was to test the hypothesis that a causal relationship exists between the level of expression of G(S)alpha and induction of the adenylyl cyclase (AC) cascade. The methodology employed transient transfection of HEK 293 cells with a cDNA for the 52-kDa form of G(S)alpha under regulation by inducible metallothionein promoters. Transfectants were exposed to varying concentrations (0-125 microM) of zinc sulfate that produced a 3-fold range of membrane G(S)alpha expression. The range of G(S)alpha expression produced was found to mimic a physiologically relevant spectrum of G(S)alpha expression in membranes derived from human tissues and rat brain. It was observed that induction of G(S)alpha expression increased constitutive as well as stimulated cAMP accumulation. Moreover, induction of G(S)alpha expression increased events distal to the accumulation of cAMP including the phosphorylation of the transcription factor, cAMP response element binding protein and transcriptional activation of cAMP-dependent reporter genes. In summary, these studies show that the amount of G(S)alpha expression has a marked impact on the level of activity of the AC cascade from the membrane through to the nucleus. It is hypothesized that individuals who differ in G(S)alpha expression may also differ in the expression of certain cAMP-dependent genes.

Bilateral simultaneous cavernous sinus sampling using corticotropin-releasing hormone in the evaluation of Cushing disease

PURPOSE

To determine whether bilateral, simultaneous, cavernous sinus sampling after corticotropin-releasing hormone (CRH) stimulation offers as accurate detection and lateralization of Cushing disease as inferior petrosal sinus sampling does.

METHODS

Seventeen consecutive patients with hypercortisolism and with high-dose dexamethasone suppression test results suggesting Cushing disease underwent bilateral cavenous sinus sampling with CRH stimulation. The diagnosis of Cushing disease was established in all patients by histologic examination or, if no tumor was found at surgery, by subtotal resection of the gland or radiation therapy resulting in eventual hypocortisolism or normal adrenal function and clinical remission.

RESULTS

The sensitivity of cavenous sinus sampling with and without CRH in detecting Cushing disease was 94% and 71%, respectively. The abnormal side of the pituitary was correctly identified in all patients who had criteria for lateralization, yielding a positive predictive value of 100%.

CONCLUSIONS

This small series suggests that cavernous sinus sampling with CRH is as accurate as inferior petrosal sinus sampling in detecting Cushing disease and perhaps more accurate in lateralizing the abnormality within the pituitary gland.

Ethanol exposure alters the phosphorylation of cyclic AMP responsive element binding protein and cyclic AMP responsive element binding activity in rat cerebellum

The purpose of the present study was to track the acute effects of ethanol on the cerebellar adenylyl cyclase cascade from membrane to nucleus and to determine how this important signaling pathway neuroadapts during chronic ethanol exposure. An acute ethanol challenge increased cyclic AMP content and protein kinase A activity by 80% compared to control rats. In the nucleus the phosphorylated form of cAMP responsive element binding protein (CREB) increased 500%. Gel retardation assays with an oligomer encoding the rat proenkephalin cyclic AMP (CRE)1 were performed. Assays from protein derived from rats acutely exposed to ethanol identified three CRE-protein complexes also observed in assays of protein from saline-treated animals. However, after acute ethanol exposure, the intensity of the upper and middle CRE-protein complexes increased by 3-fold (280 +/- 10 vs. 70 +/- 3 arbitrary units; P < .01) compared to the sham treatment. Intensity of complex formation was still elevated 1 and 6 hr after ethanol exposure compared to sham conditions. In contrast, chronic ethanol treatment as well as pair-fed treatment did not alter the phosphorylation state of CREB or the intensity of the specific CRE-protein complexes on gel retardation assays. In summary, acute ethanol exposure resulted in the activation of the adenylyl cyclase signal transduction cascade from membrane to nucleus. In contrast, chronic ethanol exposure did not alter the phosphorylation of CREB or CRE binding activity. The behavioral significance of these events remain unclear, but may be related to the development of ethanol-induced tolerance in specific cerebellar functions.

Effects of restraint stress on components of adenylyl cyclase signal transduction in the rat hippocampus

Chronic stress can injure hippocampal neurons as well as alter hippocampal function. The adenylyl cyclase (AC) signal transduction system is an important modulator of neurotransmission in this brain region. This study was conducted to begin to understand the effects of chronic stress on the hippocampal AC system. To assess dependence of type I and type II AC mRNA expression on adrenal integrity, total RNA was prepared from the hippocampus of nonstressed rats 7 days following either sham surgery or adrenalectomy (ADX). Adrenalectomy resulted in a 60% diminution in steady-state expression of type II AC mRNA (p < .005) and a nonsignificant fall in type I AC mRNA expression. Both sham and adrenalectomized rats were then exposed to 1-hour sessions of restraint, twice per day (0800 to 0900 and 1500 to 1600 hours) for 4 days. Following the stress paradigm, RNA was prepared from the hippocampus and type I and type II AC mRNA levels determined by Northern blot. Densitometic analysis showed that in comparison to unstressed sham rats, stressed sham rats had a significant twofold increase in steady-state levels of type I and type II mRNA. Stressed adrenalectomized rats also had increased expression in type II AC mRNA but no significant stress-induced change in expression of type I AC mRNA. To assess dependence of hippocampal membrane G-Proteins on adrenal integrity, hippocampal membranes from nonstressed rats 7 days following either sham surgery or adrenalectomy (ADX) were analyzed by immunoblot.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential expression of guanosine triphosphate binding proteins in men at high and low risk for the future development of alcoholism

We evaluated G-proteins that are components of adenylyl cyclase (AC) signal transduction in erythrocyte and lymphocyte membranes from 26 family history positive (FHP) non-alcoholic and 26 family history negative (FHN) nonalcoholic subjects. Subjects were classified as FHP if their father met criteria for alcohol dependence; as FHN, if there was no history of alcoholism in any first or second degree relatives. Immunoblot analysis indicated that levels of erythrocyte membrane Gs alpha from FHP subjects were greater than levels in FHN subjects (171 +/- 11 vs 100 +/- 6, P < 0.001). To confirm the results of the immunoblot analysis, Gs alpha was quantitated by cholera toxin-dependent [32P]ADP-ribosylation. Levels of erythrocyte [32P]ADP-ribose-Gs alpha from FHP subjects were greater than levels in FHN subjects (236 +/- 28 vs 100 +/- 14, P < 0.001). Gs alpha levels did not correlate with age or alcohol consumption. By contrast to differences in Gs alpha, immunoblot analysis showed similar levels of Gi(2)alpha and Gi(3)alpha in erythrocyte membranes of FHP and FHN subjects. Pertussis toxin-catalyzed [32P]ADP-ribosylation of Gi-like G-proteins confirmed the immunoblot observations. Lastly, compared to FHN subjects, FHP subjects had enhanced Gs alpha expression in lymphocyte membranes as well (138 +/- 11 vs 100 +/- 5.5; P < 0.02). In summary, compared to FHN nonalcoholic men, FHP nonalcoholic men had greater levels of the stimulatory G-protein, Gs alpha, in erythrocyte and lymphocyte membranes. Enhanced expression of Gs alpha may be a marker of increased risk for the future development of alcoholism.

Naloxone-induced activation of the hypothalamic-pituitary-adrenal axis in suspected central adrenal insufficiency

The authors studied 15 patients at risk for central adrenocortical insufficiency to evaluate the role of naloxone in establishing the integrity of the hypothalamic-pituitary-adrenal axis. Each patient was admitted to the General Clinical Research Center for 2 days. Naloxone, 125 micrograms/kg body weight, was administered intravenously, and plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations were measured at -15, 0, 30, 45, 60, 90, and 120 minutes. Metyrapone, 30 mg/kg body weight, was administered orally at 11 PM on the second day of hospitalization. Plasma ACTH, cortisol, and 11-deoxycortisol concentrations were measured at 8 AM pre- and postmetyrapone. The results of the metyrapone test were used to distinguish patients who had central adrenal insufficiency from those who were normal. In 11 patients who had a normal metyrapone test, the plasma ACTH level increased from 6 +/- 1 pmol/L at baseline to 11 +/- 2 pmol/L 30 minutes after naloxone administration. The plasma cortisol increased from 191 +/- 21 nmol/L at baseline to 379 +/- 47 nmol/L 45 minutes after naloxone administration. In four patients with central adrenal insufficiency, the plasma ACTH and cortisol concentrations did not increase after naloxone administration. Reliance solely on the individual ACTH and cortisol responses to naloxone would have permitted a correct decision regarding glucocorticoid replacement therapy in 14 (93%) of 15 patients. Naloxone stimulation testing may have a role in the clinical evaluation of patients with suspected central adrenocortical insufficiency.

Adrenocorticotropin responses following administration of ethanol and ovine corticotropin-releasing hormone in the sons of alcoholics and control subjects

Alcoholism is a familial disorder with both genetic and environmental determinants. The sons of alcoholic fathers have been documented to have alterations in several neuroendocrine measures. We investigated the ACTH/cortisol response to ovine corticotropin-releasing hormone (oCRH) and ethanol in men with and without a family history of alcoholism. Men were defined as family history positive (FHP) (n = 7) if their father was alcoholic; as family history negative (FHN) (n = 16), if their father was nonalcoholic. Ethanol (0.75 g/kg) or placebo was ingested over 15 min, 1 microgram/kg oCRH was administered, and plasma ACTH/cortisol levels were determined at -20, 0, 15, 30, 60, and 90 min after oCRH. Following placebo, FHP men had lower peak ACTH response to oCRH than did FHN men (12 +/- 2 vs 20 +/- 2 pmol/liter, P = 0.04). In FHN men, plasma ACTH response to oCRH was blunted during the ethanol session compared to the placebo session (13 +/- 1 vs 20 +/- 2 pmol/liter; P = 0.006). In contrast, FHP men had similar ACTH responses to oCRH during ethanol and placebo sessions. Cortisol responses to oCRH were similar in both groups during both sessions. In summary, FHP and FHN nonalcoholic men had different plasma ACTH responses following the administration of oCRH.

Signal-transducing G proteins: basic and clinical implications

The pivotal role that G proteins play in transmembrane signal transduction is highlighted by the rapidly expanding list of receptors and effector molecules that are coupled through G proteins. G proteins are poised to allow discrimination and diversification of cellular signals into the cytosolic milieu. The utilization of an evolutionarily conserved "GTPase clock" by G proteins, offers insight into the fundamental role these proteins play in biology. Knowledge of the implication of altered expression or function of G proteins in human disease is now emerging. It is not surprising that deficiency or expression of altered forms of these important proteins can lead to global or restricted metabolic disturbances, depending upon the distribution and role of the G protein. Human disorders, including heart failure, alcoholism, endocrine abnormalities, and neoplasia, are now recognized as due in part to altered expression or function of G proteins.

Effects of transforming growth factor beta 1 on the adenylyl cyclase-cAMP pathway in prostate cancer

We reported previously that MATLyLu rat prostate cancer cells engineered to overproduce transforming growth factor beta 1 (TGF beta 1) produce larger, more metastatic tumors in vivo. We recognized that this ability of TGF beta 1 to act as a positive modulator of prostate tumor behavior might be due to effects of TGF beta 1 on the host and/or on the tumor cells. In this study we demonstrated that the cells themselves respond to endogenously produced TGF beta 1, and that the adenylyl cyclase (AC)-cAMP pathway is affected. TGF beta 1-overproducing cells had lower membrane AC activity, lower intracellular cAMP content, and a lower Gs alpha protein level than did control cells. Prostate cancer cells were growth inhibited by 8-bromo-cAMP or forskolin, agents that elevate intracellular cAMP. Thus, TGF beta 1 overproduction affects the phenotype of the tumor cells, deliberate activation of endogenously produced latent TGF beta 1 is not required (indicating that the cells themselves are capable of activating latent TGF beta 1), and TGF beta 1 overproduction lowers the cellular concentration of the growth inhibitor cAMP. Therefore, TGF beta 1 overproduction could affect tumor behavior in vivo in part via a direct effect on the tumor cells.

The effects of mild ethanol intoxication on the hypothalamic-pituitary-adrenal axis in nonalcoholic men

Historically, ethanol exposure has been thought to stimulate the hypothalamic-pituitary-adrenal (HPA) axis. However, recent studies have demonstrated decreased responsiveness to metyrapone and insulin-induced hypoglycemia in alcoholic subjects. The present study investigated in more detail the effect of acute ethanol ingestion (0.75 g/kg) on the HPA axis in healthy nonalcoholic men (n = 14). In study 1, plasma ACTH/cortisol levels were determined basally and every 30 min over a 180-min period after the ingestion of placebo or ethanol (n = 8). When the subjects were analyzed as a group, ethanol did not alter ACTH or cortisol levels. However, in two of eight subjects, ethanol ingestion was accompanied by a rise in plasma ACTH. In study 2, ethanol or placebo was ingested over 15 min, and 1 microgram/kg ovine (o) CRH was administered (n = 9). Hormone levels were determined at 20 min before and 0, 15, 30, 60, and 90 min after iv oCRH. Compared to responses to placebo, plasma ACTH responses to oCRH were blunted during the ethanol session [peak ACTH, 14.2 +/- 1.4 vs. 20.3 +/- 3.1 pmol/L (P = 0.036); peak value minus baseline (delta), 7.3 +/- 1.4 vs. 13.4 +/- 2.6 pmol/L (P = 0.017); delta divided by baseline x 100, 131 +/- 28 vs. 197 +/- 29% (P = 0.041); area under the ACTH curve, 1082 +/- 116 vs. 1529 +/- 232 pmol/min.L (P = 0.024)]. Ethanol ingestion also significantly blunted plasma cortisol levels after oCRH compared to placebo treatment. In study 3, ethanol or placebo was ingested over 15 min, and 0.25 microgram ACTH-(1-24) was administered (n = 5). Cortisol levels, determined 20 min before and 0, 30, 60, and 90 min after ACTH treatment, were not altered by ethanol administration. In summary, mildly intoxicating doses of ethanol did not stimulate the HPA axis in six of eight subjects. However, mild intoxication significantly impaired oCRH-stimulated ACTH/cortisol secretion. We speculate that mild intoxication with ethanol may impair the ability of the HPA axis to respond to physiological stressors.

Enhanced expression of the inhibitory protein Gi2 alpha and decreased activity of adenylyl cyclase in lymphocytes of abstinent alcoholics

Ethanol exposure alters signal transduction through the adenylyl cyclase (AC) system. To elucidate the basis for this effect, we investigated the AC system in peripheral lymphocytes from abstinent alcoholic men (n = 22), actively drinking alcoholic men (n = 41), and nonalcoholic control men (n = 16). Immunoblot analysis of lymphocyte membranes from abstinent alcoholics demonstrated a 3.0-fold increase in the level of Gi2 alpha protein (p < 0.05) compared with controls. However, levels of Gs alpha protein were similar in both groups. Abstinent alcoholics had a 2.9-fold increase in Gi2 alpha mRNA (p < 0.001) and a 2.7-fold increase in Gs alpha mRNA (p < 0.03) compared with lymphocytes from control subjects. Actively drinking alcoholics, in contrast, had unaltered Gs alpha protein, Gi2 alpha protein, and Gi2 alpha mRNA levels compared with control subjects, but did have a 1.8-fold increase (p < 0.01) in Gs alpha mRNA. Consistent with enhanced Gi2 alpha expression, lymphocyte membranes from abstinent alcoholics had decreased basal, prostaglandin E1-, guanosine 5'-0-(3-thiotriphosphate)-gamma S-, and forskolin-stimulated AC activity compared with both controls and actively drinking alcoholics (p < 0.05). We conclude that lymphocyte AC is reduced during abstinence from alcohol and enhanced expression of the inhibitory G-protein, Gi2 alpha, may account for this change.

Chronic ethanol treatment increases expression of inhibitory G-proteins and reduces adenylylcyclase activity in the central nervous system of two lines of ethanol-sensitive mice

The possibility that a 7-day period of ethanol exposure could regulate expression of specific GTP-binding regulatory proteins was investigated in two distinct brain regions from two different lines of ethanol-sensitive mice. Following ethanol treatment, plasma membranes were prepared from cerebellum and pons of short and long sleep mice. Studies of membranes were performed to assess hormone-sensitive adenylylcyclase activity and to quantify expression of G-protein subunits. Immunoblot analysis showed that levels of Gi alpha(1) and Gi alpha(2) were markedly increased in cerebellar and pons membranes from ethanol-exposed mice compared to controls. Treatment of short sleep mice with ethanol enhanced ADP-ribosylation of both a 41- and a 39-40 kDa protein catalyzed by pertussis toxin. Ethanol did not alter expression of Gs alpha as assessed by immunoblot analysis, cholera toxin-dependent ADP-ribosylation, or by the ability of detergent extracted Gs alpha to reconstitute a functional adenylylcyclase in membranes from S49 cyc- murine lymphoma cells, a cell line which genetically lacks Gs alpha. Moreover, ethanol exposure did not influence levels of G(o) alpha or G beta 35-36 in either cerebellar or pons membranes. Cerebellar and pons membranes from ethanol-exposed short sleep mice demonstrated significantly less adenylylcyclase activity following stimulation with GTP, GTP gamma S, AlF, forskolin, and stimulatory ligands for three distinct receptors which couple to Gs alpha. Pretreatment of membranes with pertussis toxin reversed the ethanol-induced inhibition in adenylylcyclase activity. These observations were not limited to one line of mice but were also documented in a second line of ethanol-sensitive mice (e.g. long sleep). We conclude that ethanol exposure enhances expression of Gi alpha(1) and Gi alpha(2) in ethanol-sensitive mice, and is associated with decreased adenylylcyclase activity. Enhanced expression of Gi alpha(1) and Gi alpha(2) may contribute to impaired signal transduction in the central nervous system, and reduce the efficacy of neurotransmitters which signal through the adenylylcyclase system.

Stress alters adenylyl cyclase activity in the pituitary and frontal cortex of the rat

We hypothesized that sustained biosynthesis of proopiomelanocortropin (POMC) from the anterior pituitary during chronic stress might result in enhanced membrane adenylyl cyclase (AC) activity, facilitating amplification of the CRH signal despite falling numbers of CRH receptors. Therefore, we investigated the effects of stress on AC activity in anterior pituitaries from Sprague-Dawley rats exposed to stress. Following 12 h of intermittent, cold, swim stress, stressed rats had plasma corticosterone levels that were 10 fold higher than in nonstressed animals and showed a 40% reduction in the specific binding of 125I-CRH to anterior pituitary membranes. Moreover, stressed rats showed a 3 fold increase in anterior pituitary POMC mRNA levels. To test the hypothesis that factors released during stress enhanced the AC signal transduction system, thereby leading to increased POMC gene expression, we measured anterior pituitary cAMP and assayed AC activity from membranes prepared from anterior pituitary of control and stressed rats. Levels of cAMP were 2 fold higher in pituitaries from stressed rats compared to controls. The significant increase in cAMP was accompanied by a significant increase of AC activity. To test what component(s) of the AC complex are altered by stress, type I and II AC mRNA as well as Gs alpha, Gi(1-3) alpha and G beta protein levels were determined. Type II AC mRNA was significantly increased 1.7 fold in stressed rats compared with controls, whereas no consistent alteration in G-protein levels were detected. Enhanced AC activity following cold swim stress was not limited to the pituitary, to one line of rat, nor one type of stress. In Fisher rats, both cold swim and restraint stress enhanced AC activity in the pituitary and in the frontal cortex. In summary, stress enhances AC activity in the anterior pituitary. The increase in AC activity is associated with increased steady state levels of type II AC mRNA. Factor(s) released during stress may enhance AC signal transduction and allow for persistent elevation in POMC gene expression despite the inhibitory influences of glucocorticoids.

Chronic ethanol consumption disturbs G-protein expression and inhibits cyclic AMP-dependent signaling in regenerating rat liver

Evidence suggests that ethanol desensitizes hepatocytes to the trophic effects of hormones. Cyclic AMP-dependent signals are important regulators of intermediary metabolism, cellular proliferation and differentiation, and modulate liver growth during hepatic regeneration. The events leading to cyclic AMP accumulation after partial hepatectomy were characterized in rats consistently fed ethanol-containing diets and compared with results in rats fed isocaloric amounts of nonethanol diet to determine whether altered cyclic AMP-dependent signal transduction contributes to ethanol-associated aberrations in hepatic growth regulation. Ethanol treatment significantly inhibited hepatic accumulation of cyclic AMP after partial hepatectomy. This was most likely the result of decreased synthesis of cyclic AMP because activation of adenylyl cyclase by agents acting through receptors (e.g., glucagon or isoproterenol), GTP-binding proteins (GTP-gamma-S) and directly on adenylyl cyclase (e.g., forskolin) was significantly inhibited in ethanol-fed rats. Both homologous and heterologous desensitization contributed to this effect. beta 1-Adrenergic receptors were relatively down-regulated 6 hr after partial hepatectomy in ethanol-fed rats, whereas glucagon receptor kinetics were similar in the two groups. Liver membrane expression of GTP-binding proteins differed markedly after partial hepatectomy in ethanol-fed and pair-fed rats. Ethanol significantly inhibited post-partial hepatectomy induction of the stimulatory G protein, Gs alpha but led to overexpression of the inhibitory, G(i)2 alpha, subunit. Steady-state messenger RNA levels of these G proteins were similar in ethanol-fed and pair-fed rats, suggesting that ethanol inhibits G protein expression posttranscriptionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Case report: acromegaly and Cushing's disease in a patient with synchronous pituitary adenomas

A 40-year-old white woman presented with hirsutism, amenorrhea, generalized fatigue, diffuse weight gain, acral changes, and coarsened facial features. Physical examination revealed mild diastolic hypertension, acromegalic features, hirsutism, and seborrhea. The growth hormone concentration was elevated and did not suppress after glucose administration. Urinary free cortisol excretion was increased and was not suppressed during a 2 mg low-dose dexamethasone suppression test. Magnetic resonance imaging of the sella demonstrated a 1.3 x 1.2 x 0.8 cm pituitary adenoma. Trans-sphenoidal resection was performed, and portions of the resected tumor were analyzed by routine pathologic methods. Histopathologic and immunohistochemical findings indicated discrete growth hormone- and adrenocorticotropic hormone-producing pituitary adenomas. Coexisting acromegaly and Cushing's syndrome due to pituitary neoplasia was previously reported in two patients. However, to the authors' knowledge, this represents the first description of a patient with acromegaly and Cushing's disease resulting from discrete synchronous adenomas of the pituitary gland as defined by modern histopathologic techniques.

Diabetes insipidus

OBJECTIVES

To review the pathophysiology, diagnosis, and treatment of the syndromes of diabetes insipidus with an emphasis on those situations likely to be encountered in the critical care setting.

DATA SOURCES

Extensive clinical experience and relevant publications from the English literature identified via MEDLINE search, citation in reviews, publications of original data, and endocrine texts.

STUDY SELECTION AND DATA EXTRACTION

Landmark papers pertaining to all aspects of diabetes insipidus were selected. Reviews, primary articles, and case reports pertaining to diabetes insipidus in the critical care setting were identified and selected according to their content of clinically useful information.

DATA SYNTHESIS AND CONCLUSIONS

Diabetes insipidus may result from impaired synthesis and release of vasopressin from the hypothalamic-pituitary unit (neurogenic) or renal insensitivity to circulating vasopressin (nephrogenic). A number of interventions, diseases, and drugs commonly encountered in the critical care setting may result in the development or exacerbation of diabetes insipidus. The diagnosis of diabetes insipidus requires the exclusion of other causes of polyuria and a systematic demonstration of the response of homeostatic mechanisms to controlled dehydration. The treatment of diabetes insipidus depends on many factors, including the clinical setting, degree and pathophysiologic classification, ability of the patient to compensate for free water losses, and expected duration of the abnormality. Underlying disorders should be treated appropriately whenever possible.

Hormonal tolerance to ethanol is associated with decreased expression of the GTP-binding protein, Gs alpha, and adenylyl cyclase activity in ethanol-treated LS mice

Using the proopiomelanocortin (POMC) system as a marker, long sleep (LS) and short sleep (SS) lines of mice were investigated to explore the cellular events that occur during the acquisition of hormonal tolerance to ethanol. Four-day ethanol exposure (1.8 g/kg/24 hr) increased anterior pituitary POMC mRNA levels 4-fold in the LS line and 2-fold in the SS line. Following 7 days of ethanol exposure (1.8 g/kg/24 hr), anterior pituitary POMC levels returned to basal values in the LS line but remained elevated (2-fold) in the SS line. In this setting, the loss of ethanol's ability to sustain elevated POMC mRNA levels in the LS line is defined as hormonal tolerance. Since POMC biosynthesis is primarily regulated through adenylyl cyclase, ethanol-induced alterations in this signal transduction system were explored. Paralleling the effects of ethanol on POMC mRNA levels, ethanol exposure reduced GTP-gamma-S, AIF3-, and MnCl2-stimulated adenylyl cyclase activity by 35%, 21%, and 24%, respectively, in the LS line without effecting adenylyl cyclase activity in the SS line. To determine whether ethanol-induced changes in adenylyl cyclase activity in LS mice could result from alterations in G proteins, protein levels of G, alpha and Gi alpha were determined by western analysis before and after ethanol exposure. Paralleling the effect on POMC mRNA levels and adenylyl cyclase activity, ethanol induced a 35% reduction in Gs alpha protein levels in LS mice but did not alter Gi alpha levels. Neither Gs alpha nor Gi alpha levels were altered in the SS line.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in the hypothalamic-pituitary-adrenal axis in actively drinking alcoholics

The impact of chronic alcohol abuse on the hypothalamic-pituitary-adrenal (HPA) axis was investigated in actively drinking, nondepressed alcoholics with no evidence of liver disease. Fourteen male alcoholics and 13 matched nonalcoholics were studied. Although alcoholics and controls had similar decrements in cortisol levels after metyrapone blockade, plasma ACTH and 11-deoxycortisol levels in alcoholics were 60% (P less than 0.05) and 40% (P less than 0.05), respectively, of control values. To further clarify defects in the HPA axis of the alcoholic group, each subject underwent a CRH stimulation test. Compared to control subjects, alcoholics had a significantly blunted plasma ACTH response to CRH stimulation (P less than 0.05). Timing of the peak plasma ACTH response was altered in alcoholics. Whereas all control subjects had a peak plasma ACTH response 30 min after CRH administration, 50% of alcoholics demonstrated a peak plasma ACTH response 60 min after CRH administration, and 50% demonstrated a peak plasma ACTH response 30 min after CRH. To determine if adrenal function was also impaired, alcoholics and controls underwent a standard (250 micrograms) and a submaximal (0.250 micrograms) Cortrosyn stimulation test. Controls demonstrated a significant cortisol response to both standard and low dose Cortrosyn. Although alcoholics had a cortisol response similar to that of controls after the standard dose of Cortrosyn, they did not have a statistically significant rise in cortisol after the submaximal dose of Cortrosyn. Twenty-four-hour urinary free cortisol levels were 2-fold higher in alcoholics compared to controls. In summary, although a subset of alcoholics demonstrated enhanced basal production of cortisol, most alcoholics had a blunted response to acute intervening stress, including CRH, low dose ACTH-(1-24), and metyrapone blockade. These data suggest that alcoholics have ethanol-induced HPA axis injury, resulting in an inappropriately reduced response to nonethanol-induced stress.

A proposed role for chromogranin A as a glucocorticoid-responsive autocrine inhibitor of proopiomelanocortin secretion

Chromogranin A (CgA) is a 50 kilodalton (kDa) acidic glycoprotein that is costored and cosecreted from secretory granules with endogenous hormone from diverse endocrine cell types. The physiological role(s) of CgA is yet to be defined. In this study we used the AtT-20 mouse corticotropic cell line, which produces both CgA and POMC-derived peptides, to study 1) the regulation of CgA and POMC synthesis and secretion, and 2) the influence of CgA on POMC secretion. To study regulation of CgA and POMC biosynthesis and secretion, cells were treated with dexamethasone (DEX) or CRF for 48 h and CgA and POMC messenger RNAs and proteins were analyzed. Exposure to DEX for 48 h (10 nM) inhibited secretion of the 16 K fragment of POMC by 60% while stimulating CgA secretion 500% of control value. Consonant with these changes in protein, POMC mRNA levels fell to 40% of control levels while CgA mRNA levels increased to 250% of control values with DEX treatment. DEX treatment had no effect on the sizes of the CgA [2.1 kilobase (kb)] and POMC (1.0 kb) mRNAs. CRF (100 nM) stimulated secretion of both CgA (4-fold) and ACTH (2.5-fold) above basal values. By contrast, CRF increased POMC mRNA levels but had no effect on levels of CgA mRNA. Changes in total peptide production paralleled the changes in mRNA levels. Because DEX differentially regulated CgA and POMC synthesis and secretion, we questioned whether CgA could function as an autocrine inhibitor of hormone secretion. CgA inhibited CRF-stimulated secretion of 16 K fragment in a concentration-dependent manner (100% at 100 nM) without affecting basal 16 K fragment secretion. Moreover, anti-CgA antiserum, but not nonimmune serum, increased basal 16 K fragment secretion 2-fold and CRF-stimulated 16 K fragment secretion 1.5-fold. These results suggest that CgA plays an autocrine role as a glucocorticoid responsive inhibitor of POMC-derived peptide secretion.

Differential regulation of anterior pituitary corticotrope function is observed in vivo but not in vitro in two lines of ethanol-sensitive mice

Anterior pituitary corticotrope function was analyzed in the long sleep (LS) and short sleep (SS) lines of mice selectively bred for differences in sensitivity to ethanol. In vivo challenge with acute ethanol or CRH administration or the stress of novel handling resulted in a more pronounced increase in serum corticosterone levels in LS mice compared with SS mice. Likewise, in vivo administration of ethanol resulted in 3-fold higher levels of anterior pituitary pro-ACTH/endorphin mRNA in LS mice compared with SS mice. However, this differential regulation of the HPA axis during in vivo analysis was not observed during in vitro studies of anterior pituitary corticotrope function. Primary cultures of LS and SS anterior pituicytes responded appropriately but equivalently to a variety of secretagogues known to stimulate anterior pituitary ACTH secretion. These secretagogues included CRH (10 nM), dibutyryl-cAMP (1 mM), vasopressin (100 nM), and phorbol 12-myristate 13-acetate (10 nM). Ethanol had no direct stimulatory effect on pituitary ACTH secretion. Quantitation of anterior pituitary corticotrope peptide biosynthesis was determined by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracts from [35S]methionine-labeled anterior pituitary explants and from [35S]methionine-labeled primary cultures of anterior pituitary cells. LS mice pro-ACTH/endorphin biosynthesis in pituitary explants was 2-fold greater than pro-ACTH/endorphin biosynthesis in SS mice pituitary explants. However, in culture, isolated from hypothalamic and adrenal factors, the LS anterior pituitary pro-ACTH/endorphin biosynthetic rate became equivalent to the SS anterior pituitary pro-ACTH/endorphin biosynthetic rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Ophthalmic involvement in aggressive histiocytosis X

The authors report the clinicopathologic features of an unusually aggressive form of histiocytosis X (Langerhans' cell histiocytosis) in a 36-year-old man who presented with diplopia and early development of pituitary failure from presumed involvement of the hypothalamus. Results of postmortem examination showed infiltrates of histiocytes and mixed inflammatory cells, with a variably dense desmoplastic tissue within the orbit and sclera bilaterally, the left optic nerve, choroid, emissary canals, and many other body systems including the pituitary, heart, lung, and gastrointestinal tract. Diagnosis was confirmed by immunohistochemical staining of large histiocytes within diseased areas, with anti-T6 and anti-S-100 antibodies.

Ethanol differentially regulates proadrenocorticotropin/endorphin production and corticosterone secretion in LS and SS lines of mice

The stimulatory effects of ethanol administration on the hypothalamic-pituitary-adrenal (HPA) axis were investigated in the long sleep (LS) and short sleep (SS) lines of mice, selectively bred for differences in sensitivity to ethanol. To characterize the effects of ethanol exposure on levels of anterior pituitary pro-ACTH/endorphin mRNA, animals were treated with ethanol for either 4 or 7 days. Northern analyses of total RNA extracted from anterior pituitary indicated that ethanol-treated SS mice had 1.5-fold higher pro-ACTH/endorphin mRNA levels on day 4 and 2.5-fold higher mRNA levels on day 7 than SS control mice. Although ethanol-treated LS mice had 4-fold higher pro-ACTH/endorphin mRNA levels on day 4 compared to those in control LS mice, by day 7 pro-ACTH/endorphin mRNA levels in ethanol-treated LS mice were 40% less than LS control levels. Quantitation of pro-ACTH/endorphin-related peptide biosynthesis was determined by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracts from [35S]methionine-labeled anterior pituitary explants. Ethanol treatment for 7 days increased pro-ACTH/endorphin biosynthesis in SS mice, but decreased pro-ACTH/endorphin biosynthesis in LS mice. These results parallel the effect of ethanol on pro-ACTH/endorphin mRNA levels. Serum corticosterone levels also paralleled pro-ACTH/endorphin production in both lines of mice. In summary, ethanol acutely activates the HPA axis in SS mice, and this activation is sustained after repeated ethanol administration. In contrast, LS mice have initial activation of the HPA axis, which attenuates after repeated ethanol exposure. LS and SS mice may be appropriate models for understanding the mechanism(s) responsible for the differential activation of the HPA axis by ethanol and the development of pseudo-Cushing's syndrome in man.

Comparison of acute and chronic secretagogue regulation of proadrenocorticotropin/endorphin synthesis, secretion, and messenger ribonucleic acid production in primary cultures of rat anterior pituitary

The acute and chronic effects of secretagogues activating cAMP-dependent pathways (CRH and cAMP) and activating cAMP-independent pathways [phenylephrine and phorbol 12-myristate 13-acetate (PMA)] on anterior pituitary function were examined in serum-free cultures. Applied acutely, PMA produced a greater stimulation of ACTH/endorphin secretion than CRH or cAMP. However, the effects of CRH and cAMP on secretion were maintained for up to 12 days, while those of PMA and phenylephrine diminished rapidly. Secretagogue effects on pro-ACTH/endorphin biosynthesis were determined by immunoprecipitation of biosynthetically labeled beta-endorphin-related peptides. Cultures exposed to CRH or cAMP and [3H]tyrosine for 12 h produced 1.7 +/- 0.2- and 1.6 +/- 0.1-fold more newly synthesized beta-endorphin-related material than control cells. Cultures exposed to phenylephrine or PMA synthesized 1.3 +/- 0.1- and 1.4 +/- 0.1-fold more peptide than control cells. Exposure of cells to CRH or cAMP for 12 days increased pro-ACTH/endorphin biosynthesis to a greater extent than the 12-h treatment (3.0 +/- 0.1- and 2.5 +/- 0.3-fold over control value, respectively). Exposure to phenylephrine or PMA for 12 days had the same effect on pro-ACTH/endorphin biosynthesis as exposure for 12 h. After acute or chronic secretagogue exposure, the cells secreted relatively more newly synthesized beta-lipotropin than beta-endorphin. Levels of pro-ACTH/endorphin mRNA in cultures treated acutely (12 h) or chronically (12 days) with CRH, cAMP, or phenylephrine changed in parallel with rates of pro-ACTH/endorphin biosynthesis. In contrast, chronic exposure to PMA stimulated biosynthesis while reducing pro-ACTH/endorphin mRNA levels. In summary, these results suggest that factors that activate cAMP-dependent pathways are more powerful stimulators of pro-ACTH/endorphin biosynthesis than factors that activate cAMP-independent pathways; the cAMP-dependent pathway may be primarily responsible for regenerating depleted hormone reserves.

Alzheimer's disease: low levels of peptide alpha-amidation activity in brain and CSF

Carboxyl terminal alpha-amidation confers biologic activity to many neuropeptides. Levels of alpha-amidating activity, peptidyl-glycine alpha-amidating monooxygenase (PAM), were reduced in the CSF of patients with dementia of the Alzheimer type (DAT) compared with healthy, age-matched controls. Repeat lumbar puncture data revealed a decline in CSF PAM activity of approximately 16% per year in DAT patients. Of the cerebral cortical regions examined, only the temporal pole showed reduced PAM activity in patients with Alzheimer's disease (AD) compared with controls. These studies may indicate selective dysfunction of neurons which normally synthesize biologically active, alpha-amidated peptides in the CNS of AD patients.

Effect of chronic secretagogue exposure on pro-adrenocorticotropin/endorphin production and secretion in primary cultures of rat anterior pituitary

The effects of rat CRF, arginine vasopressin (VP), oxytocin (OXY), and isoproterenol (ISO) on the biosynthesis and release of pro-ACTH/endorphin-derived peptides by monolayer cultures of rat anterior pituitary cells in complete serum-free medium (CSFM) were studied. When cells were exposed to hormone for 3 h, CRF, VP, OXY, and ISO were each able to stimulate secretion of immunoactive hormone into culture medium. To determine the effects of chronic secretagogue exposure on corticotrope function, cultures were exposed to hormone for 14 days, and total hormone production was measured by immunoassay (cumulative hormone secreted plus cell hormone content). In the absence of CRF, total hormone production increased 3.6 +/- 0.2-fold (mean +/- SEM) over the period from 2-14 days; chronic CRF treatment brought about a 7.9 +/- 0.7-fold increase in total hormone production over the same period (P less than 0.0025) or a 2.2-fold increase over control cells. Total hormone production was not affected by chronic treatment with VP (100 nM), OXY (100 nM), or ISO (100 nM); the response of the cells to chronic CRF treatment was unaltered by chronic inclusion of VP, OXY, or ISO. To examine the chronic effects of secretagogues more directly, anterior pituitary cells were grown in control CSFM or in CSFM containing CRF or VP for 7 days and then incubated in medium containing radiolabeled amino acid for 15 min. The newly synthesized pro-ACTH/endorphin was quantified by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Cells grown in CSFM containing CRF synthesized 1.9 times more labeled pro-ACTH/endorphin that cells grown in control CSFM or in CSFM containing VP. Chronic exposure of anterior pituitary cultures to 8-bromo-cAMP stimulated both synthesis and release of pro-ACTH/endorphin-derived peptides, suggesting that a secretagogue capable of producing a sustained elevation in intracellular cAMP levels will stimulate prohormone synthesis.

Characterization of peptide alpha-amidation activity in human cerebrospinal fluid and central nervous system tissue

Peptidyl-glycine alpha-amidation activity has been detected in human cerebrospinal fluid (CSF) and in several regions of the central nervous system. Activity was monitored by measuring conversion of mono-125I-D-Tyr-Val-Gly into mono-125I-D-Tyr-Val-NH2. The alpha-amidation activity in CSF is dependent on molecular oxygen, copper ions and ascorbic acid and appears to recognize a variety of peptide substrates which contain carboxyl terminal glycine residues. Kinetic analyses demonstrated Michaelis-Menten kinetics with a Km of 4.6 microM for D-Tyr-Val-Gly. The level of peptidyl-glycine alpha-amidation activity in 14 samples of CSF averaged 43 +/- 5 pmol/ml/h (mean +/- SEM; range 11-85 pmol/ml/h) or 1.9 +/- 0.2 pmol/Mg protein/h. No difference was noted between samples from male and female subjects. Extracts of central nervous system tissue contained alpha-amidation activity. The highest levels of enzyme activity were found in the hypothalamus with lower levels in the neurohypophysis and the cerebral cortex. Still lower but detectable activity was found in the cerebellum and pons. Human peptidyl-glycine alph-amidation activity is found in central nervous system tissues known to synthesize alpha-amidated neuropeptides and may be secreted from these tissues along with alpha-amidated peptides into CSF.

Characterization of a peptide alpha-amidation activity in human plasma and tissues

Peptidyl glycine alpha-amidation activity has been detected in human plasma and in several human tissues known to synthesize biologically active alpha-amidated peptides. Activity was monitored by measuring conversion of mono-[125I]-D-Tyr-Val-Gly into mono-[125I]-D-Tyr-Val-NH2. The plasma alpha-amidation activity is dependent on molecular oxygen, copper, and ascorbic acid and appears to recognize a variety of peptide substrates which contain carboxyl terminal glycine residues. Kinetic analyses demonstrated Michaelis-Menten kinetics with a Km of 14 mumol/L for D-Tyr-Val-Gly. Based on gel filtration, the apparent molecular weight of the peptidyl glycine alpha-amidation activity in human serum is 60,000. The level of peptidyl glycine alpha-amidation activity in adult plasma (N = 17) was 106 +/- 3 pmol/mL/h (Mean +/- SEM) with no difference between male and female subjects (range 84 to 126 pmol/mL/h). In subjects under 15 years old (N = 10), mean plasma activity was 128 +/- 10 pmol/mL/h, higher than values for adult control plasma (P less than .05). In serum from hypothyroid adults (N = 13), mean serum activity was 141 +/- 11 pmol/mL/hr, higher than euthyroid controls (P less than .025). The most striking elevations in alpha-amidation activity occurred in plasma from patients with peptide-secreting tumors. Patients with medullary thyroid carcinoma (N = 19) had a mean plasma peptidyl glycine alpha-amidation activity of 142 +/- 52 pmol/mL/h (range 84 to 435 pmol/mL/h). The level of plasma alpha-amidation activity in one patient with metastatic carcinoid tumor was 560 pmol/mL/h.(ABSTRACT TRUNCATED AT 250 WORDS)

Disseminated talc granulomatosis. An unusual finding in a patient with acquired immunodeficiency syndrome and fatal cytomegalovirus infection

The association of disseminated magnesium silicate talc granulomatosis and acquired immunodeficiency syndrome is reported in a male homosexual who used intravenous drugs and who died of overwhelming cytomegalovirus (CMV) infection. Autopsy findings included widespread deposition of talc crystals in the lungs, liver, lymph nodes, bone marrow, and spleen. Typical CMV inclusions were seen in the lungs, kidneys, adrenal glands, gastrointestinal tract, and right eye. There was no evidence of malignancy. Analysis of peripheral blood neutrophil function revealed impaired chemotaxis and chemokinesis, but opsonophagocytosis had remained normal. The CMV infection in the small bowel was extensive and resulted in severe destruction of the muscularis propria and neural plexi, leading to marked dilatation and persistent diarrhea. The terminal course was marked by intractable hypotension, pneumonitis, and malnutrition, which could be attributed respectively to CMV involvement of the adrenal glands, lungs, and small bowel. The etiology and possible role of systemic talc granulomatosis in the development of immunosuppressive illness is reported herein.