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Titolo:
STUDIES ON THE ROLE OF ACTH IN THE REGULATION OF ADRENAL RESPONSIVENESS AND THE TIMING OF PARTURITION IN THE OVINE FETUS
Autore:
POORE KR; YOUNG IR; CANNY BJ; THORBURN GD;
Indirizzi:
MONASH UNIV,DEPT PHYSIOL CLAYTON VIC 3168 AUSTRALIA MONASH UNIV,DEPT PHYSIOL CLAYTON VIC 3168 AUSTRALIA
Titolo Testata:
Journal of Endocrinology
fascicolo: 2, volume: 158, anno: 1998,
pagine: 161 - 171
SICI:
0022-0795(1998)158:2<161:SOTROA>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
MOLECULAR-WEIGHT FORMS; FETAL SHEEP; HYPOTHALAMOPITUITARY DISCONNECTION; LAST 3RD; GESTATION; ADRENOCORTICOTROPIN; PEPTIDES; LAMB; PROOPIOMELANOCORTIN; HYPOPHYSECTOMY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
28
Recensione:
Indirizzi per estratti:
Citazione:
K.R. Poore et al., "STUDIES ON THE ROLE OF ACTH IN THE REGULATION OF ADRENAL RESPONSIVENESS AND THE TIMING OF PARTURITION IN THE OVINE FETUS", Journal of Endocrinology, 158(2), 1998, pp. 161-171

Abstract

A dramatic late-gestation increase in fetal plasma cortisol concentrations is critical for the timing of parturition in the sheep. This increase appears to depend upon an intact hypothalamo-pituitary unit and is characterised by increasing responsiveness of the fetal adrenal gland to ACTH. ACTH has been postulated as the critical determinant of the late-gestation cortisol increase; however, recent evidence has suggested that other factors, including the ACTH precursor, pro-opiomelanocortin, may also be involved. To further define the role of ACTH in determining the tinting of parturition and the responsiveness of the fetal adrenal gland, intact (INT/ACTH) and hypophysectomised (HX/ACTH) fetuses received a continuous infusion of ACTH((1-24)) from the time of surgery (similar to 115 days gestational age (GA)) at a rate we have previously shown to generate normal fetal cortisol concentrations and term parturition in HX fetuses. A third group of saline-infused intact fetuses (INT/SAL) served as the control group. Adrenal responsiveness was assessed by cortisol responses to ACTH((1-24)) challenges at 120, 130 and 140 days GA. There were no differences between the three groupsof fetuses in the timing of parturition, the late-gestation increase in cortisol concentrations or the size of the adrenal cortex. In both INT/SAL and INT/ACTH fetuses, there were significant increases in basal immunoreactive-ACTH concentrations with advancing GA, although no such increase was observed in HX/ACTH fetuses. The proportion of total ACTH immunoreactivity present in low molecular weight (LMW) forms in INT/ACTH fetuses was greater than that in INT/SAL fetuses, while the level of LMW ACTH in HX/ACTH fetuses was intermediate. Both ACTH((1-24))-infused groups of fetuses had dramatically enhanced adrenal responsiveness to ACTH((1-24)) at all GAs tested when compared with INT/SAT, fetuses and there was a correlation tin rank order) between the proportion of LMW ACTH immunoreactivity and adrenal responsiveness. From these observations it appears that there is a separate regulation of adrenalresponsiveness from basal cortisol concentrations and that an increase in basal cortisol concentrations can occur in the absence of an increase in basal ACTH concentrations. Furthermore, an increase in adrenalresponsiveness does not appear to predict the timing of parturition nor basal cortisol concentrations. Taken together with previous studiesit appears that ACTH plays an essential role in maintaining the growth of the fetal adrenal and enhancing its responsiveness, but a late-gestation increase in ACTH concentrations is not required to regulate basal cortisol concentrations or the timing of parturition.

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Documento generato il 30/09/20 alle ore 08:35:51