The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung

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dc.contributor.advisorStrang, L Ben_ZA
dc.contributor.authorBarker, Pierre Men_ZA
dc.date.accessioned2018-01-31T13:51:05Z
dc.date.available2018-01-31T13:51:05Z
dc.date.issued1991en_ZA
dc.description.abstractAround the time of birth, the lung switches from a secretory- to a liquid absorptive organ to enable the fetus to transit from an intra-uterine to an air-breathing environment. This study concerns hormonal control of the liquid reabsorptive mechanism in the fetal lung which allows this transition to take place. Thyroidectomy in the fetal sheep at 118 days gestation (term = 147 days) prevented the development of adrenaline- or cyclic AMP-sensitivity which, in euthyroid fetuses, resulted in the capacity to absorb lung liquid from 130 days onwards. Studies in which T₃ and T₄ were infused to thyroidectornized fetal sheep showed that T₃ was required for the normal evolution of the reabsorptive response. However, infusion of this hormone to immature fetuses (110 days) did not advance the gestation at which adrenaline-sensitive absorption is first seen. Co-infusion of T₃ and hydrocortisone showed that these 2 hormones have a powerful synergistic effect on the absorption mechanism. Within a few hours of infusion of these 2 hormones to immature fetuses, a reabsorptive response to adrenaline similar to that normally seen in mature fetuses was observed. This response was fully reversible on withdrawal of T₃ and hydrocortisone infusion, and the hormonal effect was blocked by the protein synthesis inhibitor, cyclohexirnide. These findings suggest that the normal rise in T₃ and cortisol seen in the fetus in late gestation is responsible for maturation of the liquid absorption mechanism which allows the fetus to make a transition to an independent air-breathing existence. These observations may be of significance in the clinical management of infants born prematurely, who may have had insufficient pre-natal exposure to T₃ and cortisol.en_ZA
dc.identifier.apacitationBarker, P. M. (1991). <i>The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung</i>. (Thesis). University of Cape Town ,Faculty of Health Sciences ,Division of Clinical Pharmacology. Retrieved from http://hdl.handle.net/11427/27185en_ZA
dc.identifier.chicagocitationBarker, Pierre M. <i>"The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung."</i> Thesis., University of Cape Town ,Faculty of Health Sciences ,Division of Clinical Pharmacology, 1991. http://hdl.handle.net/11427/27185en_ZA
dc.identifier.citationBarker, P. 1991. The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Barker, Pierre M AB - Around the time of birth, the lung switches from a secretory- to a liquid absorptive organ to enable the fetus to transit from an intra-uterine to an air-breathing environment. This study concerns hormonal control of the liquid reabsorptive mechanism in the fetal lung which allows this transition to take place. Thyroidectomy in the fetal sheep at 118 days gestation (term = 147 days) prevented the development of adrenaline- or cyclic AMP-sensitivity which, in euthyroid fetuses, resulted in the capacity to absorb lung liquid from 130 days onwards. Studies in which T₃ and T₄ were infused to thyroidectornized fetal sheep showed that T₃ was required for the normal evolution of the reabsorptive response. However, infusion of this hormone to immature fetuses (110 days) did not advance the gestation at which adrenaline-sensitive absorption is first seen. Co-infusion of T₃ and hydrocortisone showed that these 2 hormones have a powerful synergistic effect on the absorption mechanism. Within a few hours of infusion of these 2 hormones to immature fetuses, a reabsorptive response to adrenaline similar to that normally seen in mature fetuses was observed. This response was fully reversible on withdrawal of T₃ and hydrocortisone infusion, and the hormonal effect was blocked by the protein synthesis inhibitor, cyclohexirnide. These findings suggest that the normal rise in T₃ and cortisol seen in the fetus in late gestation is responsible for maturation of the liquid absorption mechanism which allows the fetus to make a transition to an independent air-breathing existence. These observations may be of significance in the clinical management of infants born prematurely, who may have had insufficient pre-natal exposure to T₃ and cortisol. DA - 1991 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1991 T1 - The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung TI - The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung UR - http://hdl.handle.net/11427/27185 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/27185
dc.identifier.vancouvercitationBarker PM. The role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lung. [Thesis]. University of Cape Town ,Faculty of Health Sciences ,Division of Clinical Pharmacology, 1991 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/27185en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDivision of Clinical Pharmacologyen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherEpinephrine.en_ZA
dc.subject.otherFetal Organ Maturity - physiology.en_ZA
dc.subject.otherLung - Embryology.en_ZA
dc.subject.otherSteroids - physiologyen_ZA
dc.subject.otherThyroid hormonesen_ZA
dc.titleThe role of thyroid and steroid hormones in maturation of the adreline-sensitive reabsorptive mechanism of the fetal lungen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameMDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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