Endotoxin has been shown to stimulate ACTH and cortisol secretion through an action at the hypothalamic level. However, the nature of hypothalamic neurohormones, corticotropin-releasing hormone (CRH) and especially arginine vasopressin (AVP), involved in that regulation is still controversial. The purpose of this study was to determine the effects of an acute i.v. endotoxin administration on CRH and AVP secretion into hypophysial portal blood (HPB). The experiment has been performed in sheep since it is possible to collect HPB and quantify CRH and AVP secretion in this animal under physiological conditions. The release of both peptides into HPB was stimulated by endotoxin injection, the increase in portal AVP being more pronounced than that of CRH. An initial, transient, increase in jugular AVP concentrations was observed, probably due to the activation of magnocellular AVP neurons. In conclusion, our data indicate that the activation of the pituitary-adrenal axis after endotoxin injection is associated with an increased release of both CRH and AVP into HPB. Magnocellular AVP neurons are initially stimulated while parvocellular CRH and AVP neurons are stimulated throughout the experiment.
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F Dadoun, V Guillaume, N Sauze, J Farisse, JG Velut, JC Orsoni, R Gaillard, and C Oliver
B Conte-Devolx, V Guillaume, F Boudouresque, N Graziani, E Magnan, M Grino, N Emperaire, K Nahoul, M Cataldi, and C Oliver
The effects of rapid changes of circulating cortisol levels on ACTH secretion and on corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) concentrations into hypophysial portal blood were studied in six adult rams. Pharmacological adrenalectomy was obtained by 3 h metyrapone infusion (100 mg·kg−1·h−1). Blockade of cortisol synthesis induced a tenfold increase of plasma ACTH levels accompanied by a moderate increase of CRF secretion (150% vs preinjection levels) and a large increment of AVP secretion (535% vs preinjection levels). ACTH levels remained high during the 3 h following the end of metyrapone infusion. During the same period, CRF secretion was still elevated (231% vs preinjection levels), while AVP secretion was further stimulated (2,151% vs preinjection levels). Subsequent hydrocortisone infusion (66 μg·kg−1·h−1) for 2 h induced a rapid decrease of both ACTH and AVP secretion, while CRF levels in hypophysial portal blood still remained elevated. These data suggest that changes in ACTH secretion induced by acute modifications of the negative glucocorticoid feedback are, in addition to the well documented direct effect of cortisol on the corticotropes, mainly mediated by variations of hypothalamic AVP secretion.
Ann McCormack, Olaf M Dekkers, Stephan Petersenn, Vera Popovic, Jacqueline Trouillas, Gerald Raverot, Pia Burman, and ESE survey collaborators
To collect outcome data in a large cohort of patients with aggressive pituitary tumours (APT)/carcinomas (PC) and specifically report effects of temozolomide (TMZ) treatment.
Electronic survey to ESE members Dec 2015–Nov 2016.
Reports on 166 patients (40 PC, 125 APT, 1 unclassified) were obtained. Median age at diagnosis was 43 (range 4–79) years. 69% of the tumours were clinically functioning, and the most frequent immunohistochemical subtype were corticotroph tumours (45%). Ki-67 index did not distinguish APT from PC, median 7% and 10% respectively. TMZ was first-line chemotherapy in 157 patients. At the end of the treatment (median 9 cycles), radiological evaluation showed complete response (CR) in 6%, partial response (PR) in 31%, stable disease (SD) in 33% and progressive disease in 30%. Response was more frequent in patients receiving concomitant radiotherapy and TMZ. CR was seen only in patients with low MGMT expression. Clinically functioning tumours were more likely to respond than non-functioning tumours, independent of MGMT status. Of patients with CR, PR and SD, 25, 40 and 48% respectively progressed after a median of 12-month follow-up. Other oncological drugs given as primary treatment and to TMZ failures resulted in PR in 20%.
This survey confirms that TMZ is established as first-line chemotherapeutic treatment of APT/PC. Clinically functioning tumours, low MGMT and concurrent radiotherapy were associated with a better response. The limited long-term effect of TMZ and the poor efficacy of other drugs highlight the need to identify additional effective therapies.