Reasons for palliative treatments in stage III non-small-cell lung cancer: what contribution is made by time-dependent changes in tumour or patient status?

INTRODUCTION: Stage iii lung cancer is the most advanced stage of lung cancer for which the potential of curative treatment is often discussed. However, a large proportion of patients are treated with palliative intent. An understanding of the time-dependent and -independent factors contributing to the choice of palliative-intent treatment is needed to help optimize patient outcomes. METHODS: This retrospective cohort study of patients with stage iii non-small-cell lung cancer (nsclc) newly diagnosed between 1 January 2008 and 31 December 2012 at the Cancer Centre of Southeastern Ontario collected data including patient demographics, clinical characteristics, tumour characteristics, treatment, and outcomes. RESULTS: Of 237 patients with stage iii nsclc included in the study, 130 were not treated with radical or curative intent (55%). Major time-independent variables cited for palliative-intent treatment included extreme age (5%), comorbidity (27%), patient choice (5%), and poor lung function (5%). Time-dependent variables included tumour progression on imaging (15%), weight loss (33%), performance status (32%), and the occurrence of a major complication such as hemoptysis, lung collapse, or pulmonary embolism (7%). A significant number of patients (20%) experienced a decline in performance status-to 2, 3, or 4 from 0 or 1-over the course of the diagnostic journey, and 12% experienced a transition from no weight loss to more than 10% weight loss. CONCLUSIONS: A significant proportion of patients receive palliative therapy for stage iii nsclc because of changes that occur during the diagnostic journey. Shortening or altering that pathway to avoid tumour growth or patient deterioration during care could allow for more patients to be treated with curative intent.

Causes of death and subsequent treatment after initial radical or palliative therapy of stage III non-small-cell lung cancer.

INTRODUCTION: Stage iii lung cancer is the most advanced stage of lung cancer for which radical (potentially curative) treatment is often discussed. Understanding the reasons for mortality and subsequent treatments in patients with stage iii non-small-cell lung cancer (nsclc) is important. METHODS: This retrospective cohort study extracted demographic, clinical, treatment, and outcomes data for patients with newly diagnosed stage iii nsclc diagnosed between 1 January 2008 and 31 December 2012 at a single institution. RESULTS: The study included 237 patients with stage iii nsclc, 130 of whom were not treated with radical or curative intent (55%). Median survival in the entire cohort was 14 months from diagnosis. For patients treated with radical-intent therapy, causes of death varied with the time period. The hazard rate for death was approximately 2.8 per 100 person-months of follow-up over the entire disease course and was highest between 6 months and 24 months. Over the entire time period, local causes accounted for 29% of deaths; systemic non-central nervous system metastases, for 25%; and brain metastases, for 14%. For patients treated with palliative intent, the overwhelming cause of death was local disease complications or progression (56% of deaths). Only 12% of patients in the palliative treatment group who progressed received subsequent chemotherapy; 23% of patients in the radical group who progressed received palliative chemotherapy. The most frequent subsequent treatment in both groups was radiation therapy. CONCLUSIONS: The eventual life-ending event in stage iii nsclc varied for the patients who qualified for, and were treated with, radical or curative intent and for the patients who received palliative-intent therapy. Utilization of systemic chemotherapy in patients not fit for radical therapy is low.

A population-based study of pulmonary monitoring and toxicity for patients with testicular cancer treated with bleomycin.

Background: Bleomycin is commonly used to treat advanced testicular cancer and can be associated with severe pulmonary toxicity. The primary objective of the present study was to describe the use of pulmonary function tests (pfts) and chest imaging before, during, and after treatment with bleomycin. Methods: To identify all incident cases of testicular cancer treated with bleomycin-based chemotherapy in the Canadian province of Ontario during 2005-2010, the Ontario Cancer Registry was linked with chemotherapy treatment records. Health administrative databases were used to describe use of pfts, chest imaging, and physician visits for respiratory complaints. Results: Of 394 patients treated with orchiectomy and chemotherapy who received at least 1 dose of bleomycin, 93% had complete chemotherapy records available. In the 4 weeks before, during, and within 2 years after finishing bleomycin-based chemotherapy, pfts were performed in 17%, 17%, and 29% of patients respectively. Chest imaging was performed in 68%, 62%, and 98% of patients in the same time periods. In the 2 years after bleomycin-based chemotherapy, 23% of treated patients had a physician visit for respiratory symptoms. That rate was substantially higher for men with greater exposure to bleomycin: 40% (24 of 60) for 10-12 doses bleomycin compared with 21% (53 of 250) for 7-9 doses and with 14% (8 of 58) for 1-6 doses (p = 0.002). Conclusions: Quality improvement initiatives are needed to increase baseline rates of chest imaging within 4 weeks of starting chemotherapy for testicular cancer; to understand why such a high proportion of men have chest imaging during bleomycin-based chemotherapy; and to mitigate the excess pulmonary toxicity seen with increasing exposure to bleomycin.

Venous Thromboembolism During Chemotherapy for Testicular Cancer: A Population-Based Study.

AIMS: Venous thromboembolism (VTE) is a potential complication among germ cell tumour patients. We evaluated the incidence rate, timing and factors associated with VTE among patients with germ cell cancer in routine practice. MATERIALS AND METHODS: The Ontario Cancer Registry was linked to electronic records of treatment to identify all cases of testicular cancer treated in Ontario during 2000-2010. Administrative databases were used to identify VTE in the 3 months before and 5 years after orchiectomy. We explored patient-, disease- and treatment-related factors associated with VTE among all patients as well as those with detailed chemotherapy records available. RESULTS: During 2000-2010, 2650 patients underwent orchiectomy for testicular cancer; among this cohort, 920 (33%) received chemotherapy. The VTE rate was 8% (69/920) among patients treated with chemotherapy and 0.6% (11/1730) among those without chemotherapy. Among the patients treated with chemotherapy who had VTE, 13% (9/69) occurred in the month before starting chemotherapy, 62% (42/69) in the first 3 months after starting and 25% thereafter. For patients who received three and four cycles, VTE rates were 8% (21/258) and 16% (19/121), respectively. In adjusted analyses, the only factor independently associated with VTE was increasing number of cycles (odds ratio 3.91 for four cycles, odds ratio 1.63 for three cycles (P = 0.022) compared with one to two cycles). CONCLUSION: This population-based study confirms findings from institutional case series regarding the high rate of VTE among patients with germ cell tumours treated with chemotherapy. Future studies should evaluate the extent to which VTE prophylactic strategies might mitigate this risk.

Oxytocin, vasopressin, and estrogen-stimulated neurophysin: daily patterns of concentration in cerebrospinal fluid.

The concentrations of oxytocin, arginine vasopressin, and estrogen stimulated neurophysin in cerebrospinal fluid of monkeys showed a daily fluctuation with high concentrations occurring during the light period. The patterns of oxytocin and estrogen-stimulated neurophysin in the cerebrospinal fluid were not observed in the plasma nor were they altered after the administration of a dose of estradiol that increased concentrations of estrogen-stimulated neurophysin in plasma. The disassociation between these cerebrospinal fluid and plasma patterns and values suggests that the secretory activity of neurons that release estrogen-stimulated neurophysin and oxytocin into the cerebrospinal fluid is controlled by mechanisms different from those that control their release into the plasma.

Vasopressin and neurophysin: high concentrations in monkey hypophyseal portal blood.

Vasopressin and its binding protein, neurophysin, were measured by radioimmunoassay in the hypophyseal portal blood of monkeys after cannulation of individual long portal veins. Mean vasopressin concentrations (13,800 picograms per milliliter) in portal blood were more than 300 times as high as those in the systemic circulation (42 picograms per milliliter). Neurophysin concentration was approximately 25 times as high in portal as in systemic blood. By immunoperoxidase techniques, high concentrations of neurophysin were demonstrated around portal capillaries of the median eminence. These studies indicate direct secretion of vasopressin and neurophysin into the portal circulation; the quantities secreted during stress may be sufficient to exert significant effects on secretion of anterior pituitary hormone.

Neurotoxicity Among Survivors of Testicular Cancer: A Population-based Study.

AIMS: Neurotoxicity may affect the quality of life of survivors of testicular cancer. Understanding the burden of neurotoxicity is important to guide survivorship care. A population-based study was undertaken to describe the proportion of patients in the 'real world' with neurotoxicity. MATERIALS AND METHODS: A population-based, retrospective, cohort study of patients with advanced testicular cancer treated in the province of Ontario. The Ontario Cancer Registry was linked to electronic treatment records to identify all incident cases of testicular cancer during 2000-2010. Administrative databases were used to describe health system visits for symptoms potentially related to neurotoxicity. Health system visit rates were explored by number of chemotherapy cycles among patients treated during 2005-2010 for whom complete chemotherapy details were available. RESULTS: During 2000-2010, 2650 patients underwent an orchiectomy for testicular cancer; 920 (33%) also received chemotherapy. The proportion of patients with health system visits for neurotoxicity in the 2 years before surgery compared with the 2 years after surgery remained stable among patients treated with orchiectomy alone (18% [303/1730] versus 18% [316/1730], P = 0.523); however, there was a substantial increase among patients treated with chemotherapy (16% [151/920] versus 25% [231/920], P < 0.001). Among patients treated with chemotherapy in 2005-2010 for whom complete details were available regarding number of treatment cycles there was a dose-response effect. The increase in health system visits for neurotoxicity from 2 years before compared with 2 years after orchiectomy was greater among patients treated with four cycles of chemotherapy (17% [21/121] versus 37% [45/121]) and three cycles of chemotherapy (17% [45/258] versus 28% [72/258]) compared with those treated with one to two cycles of chemotherapy (<13% [<6/45] versus 20% [9/45], P = 0.013). CONCLUSIONS: This population-based study suggests that symptoms of neurotoxicity are common among survivors of testicular cancer and that this seems to be driven by increasing exposure to chemotherapy. Clinicians should carefully evaluate patients for neurotoxicity during the survivorship phase of treatment.

Isolation, assay, and secretion of individual human neurophysins.

Human neurophysin was isolated from acetone-dried human posterior pituitaries and separated into two major neurophysin peptides by ion exchange chromatography and into four major peptides by preparative disk gel electrophoresis. Antisera raised in rabbits distinguished only two specific antigenic sites on the isolated neurophysin peptides. Individual sensitive and specific radioimmunoassays for two human neurophysins were developed. These assays were used to measure each neurophysin in unextracted human plasma. The two neurophysins are secreted independently in man. One assay measures a neurphysin that is specifically secreted in response to estrogen administration, estrogen-stimulated neurophysin (ESN). The other assay measures a neurophysin that is specifically secreted in response to cigarette smoking, nicotine-stimulated neurophysin (NSN). The mean ESN is 1.1 ng/ml plus or minus 0.7 SD in women and 1.0 ng/ml plus or minus 0.7 SD in men. The mean NSN is 0.9 ng/ml plus or minus 0.2 SD in women and 0.6 ng/ml plus or minus 0.3 SD in men. It is proposed that these may prove to be a specific human "oxytocinneurophysin," ESN, and a human "vasopressin-neurophysin," NSN.

Elevation of plasma neurophysin in women on oral contraceptives.

The effect of oral contraceptives on the neurohypophysis was demonstrated by changes in the plasma level of a posterior pituitary protein. neurophysin. Neurophysins are intraneuronal proteins associated with oxytocin and vasopressin. They have been shown to be released into the bloodstream. The resting plasma level of neurophysin in normal nonpregnant women is 0.69 ng/ml+/-0.7 SD. In women on oral contraceptives, the plasma level is 6.4 ng/ml+/-4.2 SD (P<0.001). Estrogen rather than progesterone causes the elevated neurophysin. The effect is observed within 12-24 h of estrogen administration and disappears 3-11 days after estrogen is discontinued. The results indicate that oral contraceptives act on the neurohypophysis and that estrogen is a potent pharmacologic stimulus useful in studying synthesis and release of neurophysin.

Cerebrospinal fluid and ependymal neurophysin.

Neurophysins are "carrier proteins" associated with vasopressin and oxytocin in the neurohypophyseal system. The release of these hormone associated proteins may serve as an indicator of posterior pituitary function. This report describes the measurement of neurophysin in human and monkey plasma and cerebrospinal fluid (CSF) by radioimmunoassay. Tissue neurophysin is also localized in monkey brain by the immunoperoxidase technique. CSF from 68 patients and five monkeys had easily measurable neurophysin in every sample. The concentration of neurophysin in CSF and in plasma of man is 5.4+/-0.30 ng/ml (mean and SEM) and 0.69+/-0.04, respectively. The two means were significantly different (P < 0.001). In paired plasma and CSF specimens which were obtained simultaneously from each of 13 human and five monkey donors, the concentrations of neurophysin in CSF were greater than those of plasma in every case (paired t test, P < 0.001). Neurophysin administered intravenously to dogs did not enter CSF. Using the immunoperoxidase technique, we found neurophysin not only in the supraoptic and paraventricular nuclei, their tracts, and the posterior pituitary, but also in the specialized ependymal tanycytes of the infundibular recess of the third ventricle and in the external layer of the median eminence where capillaries drain into hypophyseal portal vessels. Neurophysin may pass from CSF to portal vessels via tanycytes in a manner similar to that postulated for releasing factors.

Vasopressin stimulation of adrenocorticotropin hormone (ACTH) in humans. In vivo bioassay of corticotropin-releasing factor (CRF) which provides evidence for CRF mediation of the diurnal rhythm of ACTH.

The diurnal response of ACTH release to intravenously administered arginine vasopressin was tested in normal volunteers given consecutively moderate doses of vasopressin every 15 min (0.1, 0.3, 1.0, and 3.0 IU) at 2200 h and again at 0700 h (PM/AM). This protocol was repeated 4 wk later with the times reversed (AM/PM). A dose-related increase in ACTH secretion was observed in all subjects. When the AM response of the AM/PM protocol was compared with the PM response of the PM/AM protocol, the release of ACTH was greater in the morning (P less than 0.05) as evaluated by the following criteria: peak value of ACTH (129.9 +/- 30.4 pg/ml in the AM vs. 57.1 +/- 20.2 in the PM); area under the curve (689 in the AM vs. 259 in the PM); and, sensitivity of the ACTH dose-response curve (first significant increase in ACTH with 1 IU of vasopressin in the AM but not significant even after 3 IU in the PM). In addition, when the AM vasopressin testing followed a previous evening stimulation (PM/AM protocol), there was a blunted ACTH response compared with the AM/PM protocol. Corticotropin-releasing factor (CRF) is probably the major ACTH secretagogue, but since vasopressin acts synergistically with CRF to produce an augmented release of ACTH, we suggest that the ACTH response to administered vasopressin depends upon the ambient endogenous level of CRF. We interpret our data and published data that CRF produces a lesser release of ACTH in the AM as follows: in the morning endogenous CRF is high and administered CRF produces little further release of ACTH, but administered vasopressin acting synergistically with high endogenous CRF causes a greater release of ACTH; conversely, in the evening endogenous CRF is low and administered CRF causes a greater release of ACTH, but vasopressin (a weak secretagogue by itself) gives a low ACTH response. We conclude that vasopressin stimulation of ACTH secretion can be used as an in vivo bioassay of endogenous CRF, and that there is a diurnal rhythm of CRF in hypophyseal portal blood.

Changes in the metabolic clearance of vasopressin and in plasma vasopressinase throughout human pregnancy.

Metabolic clearance rates (MCR) of arginine vasopressin (AVP) were measured serially in five women starting before conception, during gestational weeks 7-8 (early), 22-24 (middle), and 36-38 (late pregnancy), and again 10-12 wk postpartum. Hormonal disposal rates were determined after water loading to suppress endogenous AVP release using a constant infusion method designed to achieve three different steady-state concentrations of plasma AVP (PAVP) on each test occasion. Dose schedules were altered in mid- and late pregnancy to obtain comparable AVP levels at each stage of the protocol. Prehydration decreased plasma osmolality sufficiently to suppress AVP release, as circulating AVP-neurophysin measured serially in three of the women was undetectable. The MCR of AVP was similar before conception (0.75 +/- 0.31, 0.79 +/- 0.34, and 0.76 +/- 0.28 liters/min at PAVP of 2.6 +/- 1.9, 4.7 +/- 2.4, and 8.3 +/- 3.9 pg/ml), in early pregnancy (0.89 +/- 0.34, 0.97 +/- 0.04, and 0.95 +/- 0.40 liters/min at PAVP of 2.2 +/- 2.1, 3.9 +/- 3.2, and 7.9 +/- 3.4 pg/ml), and postpartum (0.70 +/- 0.21, 0.69 +/- 0.24, and 0.75 +/- 0.20 liters/min at PAVP 3.5 +/- 1.8, 5.1 +/- 3.7, and 9.1 +/- 4.2 pg/ml). Values at mid-pregnancy (2.8 +/- 1.3, 3.0 +/- 1.2, and 2.7 +/- 1.2 liters/min at PAVP 2.3 +/- 2.2, 4.0 +/- 3.6, and 7.7 +/- 3.9 pg/ml) and late pregnancy (3.2 +/- 1.4, 3.3 +/- 1.4, and 2.9 +/- 1.2 liters/min at PAVP 1.9 +/- 2.0, 3.8 +/- 2.6, and 7.4 +/- 4.1 pg/ml) increased 3-4-fold (all P less than 0.01). Plasma vasopressinase, undetectable at 7-8 gestational wk, increased markedly by mid- and slightly more by late gestation. Finally, relationships between PAVP and urine osmolality were similar before, during, and after pregnancy. We conclude that marked increments in the MCR of AVP occur between gestational weeks 7 and 8 and mid-pregnancy, which parallel the period of greatest rise in both trophoblastic mass and plasma vasopressinase. There was no evidence of a renal resistance to AVP during gestation.

Hyponatremia in rats induces downregulation of vasopressin synthesis.

Hyponatremia due to inappropriate secretion of vasopressin is a common disorder in human pathophysiology, but vasopressin synthesis during hypoosmolality has not been investigated. We used a new method to quantitate synthesis of vasopressin in rats after 3, 7, and 14 d of hyponatremia induced by administering dDAVP (a vasopressin agonist) and a liquid diet. Vasopressin synthesis was completely turned off by 7 d. Vasopressin mRNA levels in the hypothalamus paralleled the reduction in synthesis and were reduced to levels of only 10-15% of the content in control rats. When hyponatremia was corrected by withdrawal of dDAVP, vasopressin mRNA slowly returned to normal over 7 d. The observation that vasopressin synthesis can be so completely turned off leads to several conclusions: under normal physiological conditions the neurohypophysis is chronically upregulated; there must be an osmotic threshold for initiation of vasopressin synthesis (and release); the large store of hormone in the posterior pituitary is essential for vasopressin to be available during times of decreased synthesis; and, finally, some nonosmolar stimulus for synthesis must be present during clinical disorders when vasopressin is secreted (and synthesized) despite hypoosmolality.

Isolation and characterization of a hormone-producing cell line from human small cell anaplastic carcinoma of the lung.

A continuous cell culture line was established from a bone marrow metastasis of small cell anaplastic carcinoma of the lung. The cultures were characterized by light and electron microscopy, and an unusual concentric arrangement of cells was observed, both in sectioned material from the patient's tumor and from the cell cultures. The cells had two types of specialized cell junctions and contained secretory-like granules of the type described in neuroendocrine cells. Lactic dehydrogenase isozyme patterns were the same as those observed in normal human serum, and the karyotype revealed the presence of several marker chromosomes. Vasopressin was present in the cells and secreted into the culture medium in the absence of neurophysin, as shown by the immunoperoxidase technique and radioimmunoassay. Oxytocin was also absent from cells.

Extending standard testing period in honeybees to predict lifespan impacts of pesticides and heavy metals using dynamic energy budget modelling.

Concern over reported honeybee (Apis mellifera spp.) losses has highlighted chemical exposure as a risk. Current laboratory oral toxicity tests in A. mellifera spp. use short-term, maximum 96 hour, exposures which may not necessarily account for chronic and cumulative toxicity. Here, we use extended 240 hour (10 day) exposures to examine seven agrochemicals and trace environmental pollutant toxicities for adult honeybees. Data were used to parameterise a dynamic energy budget model (DEBtox) to further examine potential survival effects up to 30 day and 90 day summer and winter worker lifespans. Honeybees were most sensitive to insecticides (clothianidin > dimethoate ≫ tau-fluvalinate), then trace metals/metalloids (cadmium, arsenic), followed by the fungicide propiconazole and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). LC50s calculated from DEBtox parameters indicated a 27 fold change comparing exposure from 48 to 720 hours (summer worker lifespan) for cadmium, as the most time-dependent chemical as driven by slow toxicokinetics. Clothianidin and dimethoate exhibited more rapid toxicokinetics with 48 to 720 hour LC50s changes of <4 fold. As effects from long-term exposure may exceed those measured in short-term tests, future regulatory tests should extend to 96 hours as standard, with extension to 240 hour exposures further improving realism.

Genetic influences on social attention in free-ranging rhesus macaques.

An ethological approach to attention predicts that organisms orient preferentially to valuable sources of information in the environment. For many gregarious species, orienting to other individuals provides valuable social information but competes with food acquisition, water consumption and predator avoidance. Individual variation in vigilance behaviour in humans spans a continuum from inattentive to pathological levels of interest in others. To assess the comparative biology of this behavioural variation, we probed vigilance rates in free-ranging macaques during water drinking, a behaviour incompatible with the gaze and postural demands of vigilance. Males were significantly more vigilant than females. Moreover, vigilance showed a clear genetic component, with an estimated heritability of 12%. Monkeys carrying a relatively infrequent 'long' allele of TPH2, a regulatory gene that influences serotonin production in the brain, were significantly less vigilant compared to monkeys that did not carry the allele. These findings resonate with the hypothesis that the serotonin pathway regulates vigilance in primates and by extension provoke the idea that individual variation in vigilance and its underlying biology may be adaptive rather than pathological.

Levels of neurohypophyseal peptides in the rat during the first month of life. I. Basal levels in plasma, pituitary, and hypothalamus.

Vasopressin, oxytocin, and neurophysin were measured by RIA in the pituitary, hypothalamus, and plasma (except oxytocin) of the rat during the first month of life. In plasma, vasopressin was less than 1.7 microU/ml in most animals. Neurophysin was elevated above adult levles on day 2 and decreased with age. The three peptides were present in the pituitary at birth, but in amounts less than 1% of the adult level. The vasopressin content of the pituitary increased rapidly in the first days after birth, while the levels of oxytocin and neurophysin remained low until 8 days and then increased between 8-21 days. The ratio of vasopressin to oxytocin in the pituitary was 4.4 at birth and reached unity (the ratio in the adult) at 30 days. At birth, the moles of neurophysin in the pituitary relative to the moles of hormone (oxytocin plus vasopressin) was low (0.15), largely due to a molar excess of vasopressin. The ratio of neurophysin to hormone reached unity at 21-30 days. Assays to detect vasotocin gave negative results. It is postulated that a precursor neurophysin which was related to vasopressin was present in the fetal rat but was not measured in our study.

Levels of neurohypophyseal peptides in the rat during the first month of life. II. Response to physiological stimuli.

Levels of vasopressin, oxytocin, and neurophysin were measured by RIA in the hypothalamus, pituitary, and plasma of infant rats (2-30 days old). At all ages, ip injection of a hypertonic solution of 5 g/100 ml NaCl produced a marked increase in levels of vasopressin and neurophpysin in plasma, up to 21 microU/ml and 51 ng/ml, respectively. After dehydration, there was a decrease of 26-38% in the levels of neurohypophyseal peptides in the pituitary. Depletion of neurohypophyseal peptides from the pituitary was greater after 24 h of dehydration in younger rats (26%) than in older rats (7%). Levels of vasopressin in plasma were less than 1.7 microU/ml after dehydration in younger rats but were greater in older rats. Immaturity of the neurohypophysis may contribute to the inability of newborn rats to withstand prolonged dehydration.

Plasma neurophysin levels in monkeys: emphasis on the hypothalamic response to estrogen and ovarian events.

Specific radioimmunoassays for human neurophysins released in response to estrogen (estrogen-stimulated neurophysin, ESN) and nicotine (nicotine-stimulated neurophysin, NSN) have been used to measure two similar neurophysins in rhesus monkey plasma. As in the human, concentrations of rhesus monkey neurophysins in plasma were specifically produced a marked increase of plasma NSN concentrations in the monkey. Estradiol benzoate administered intramuscularly consistently produced an increase in plasma ESN concentrations in normal cycling and castrate monkeys. ESN response to estrogen was exclusively positive and occurred approximately 10 hours after an injection of estradiol benzoate intramuscularly. Plasma samples obtained throughout the mid-cycle were measured and a characteristic rise in estrogen and LH, and a more prolonged rise in ESN were found. Our data indicate that the ESN and LH responses to estrogen stimulation are temporally related events and that the assay of ESN in plasma may be of unique value as it directly reflects the hypothalamic response to changes in estrogen secretion.

Identification of a corticotropin-releasing factor-binding protein in the plasma membrane of AtT-20 mouse pituitary tumor cells and its regulation by dexamethasone.

CRF stimulates the synthesis and secretion of proopiomelanocortin-derived peptides from AtT-20 mouse pituitary tumor cells. This study has shown that there is a specific binding site for CRF located on the plasma membrane of these cells. Both [125I]iodo-Tyr0CRF and noniodinated CRF (10(-11)-10(-7) M) stimulated, in a dose-dependent manner, the secretion of equimolar amounts of beta-endorphin-like immunoactivity from AtT-20 cells. Disuccinimidyl suberate, a cross-linking agent, was used to demonstrate specific binding of [125I]iodo-Tyr0CRF to plasma membranes from these cells. After cross-linking [125I] iodo-Tyr0CRF, the membrane proteins were solubilized with sodium dodecyl sulfate and electrophoresed on a 10% polyacrylamide gel. A single radioactively labeled band, corresponding to a mol wt of 66,000, was identified by autoradiography. [125I]Iodo-Tyr0CRF binding to these membranes was inhibited by 10(-7) M unlabeled CRF or an equimolar concentration of the CRF analog sauvagine. Similar concentrations (10(-7) M) of TRH, GnRH, insulin, [Arg8]vasopressin, somatostatin, and ACTH did not inhibit [125I]iodo-Tyr0CRF binding to the plasma membranes. Incubation of AtT-20 cells for 24 h in the presence of 10 nM dexamethasone reduced [125I]iodo-Tyr0CRF binding by 80% compared to that in untreated cells. Dexamethasone also inhibited the CRF-stimulated beta-endorphin-like immunoactivity secretory response. These data indicate that binding of CRF to a specific membrane protein is an integral component in the stimulation of AtT-20 cells by CRF.