Related Experiment Video
Updated: Apr 19, 2026
Development of a Neonatal Piglet Acute Lung Injury Model Recreating the Early Environment of Preterm Infant Lungs
Published on: October 31, 2025
Endogenous angiotensins and catecholamines do not reduce skin blood flow or prevent hypotension in preterm piglets
Yvonne A Eiby1, Eugenie R Lumbers2, Michael P Staunton1
1UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia.
Insights
Preterm piglets show immature cardiovascular responses to stress, with reduced vasoconstriction despite adequate catecholamines. Prenatal glucocorticoids may alter hormonal balance, potentially worsening this response.
Area of Science:
- Physiology
- Endocrinology
- Neonatal Medicine
Background:
- Cardiovascular function in preterm infants may be immature, impacting treatment effectiveness.
- Adrenergic treatments are often less effective in preterm infants with cardiovascular compromise.
Purpose of the Study:
- To investigate the cardiovascular and hormonal stress responses in preterm piglets.
- To compare these responses with those of term piglets.
Main Methods:
- Preterm and term piglets were studied, with some preterm piglets receiving prenatal glucocorticoids.
- Hypoxia was induced to stimulate cardiovascular responses.
- Measurements included blood pressure, skin blood flow, heart rate, and plasma hormone levels (epinephrine, norepinephrine, angiotensin II, angiotensin-(1-7), cortisol).
Main Results:
- Term piglets exhibited vasoconstriction during hypoxia; preterm piglets showed a blunted response.
- Preterm piglets had lower blood pressure and a delayed response to hypoxic stress.
- Despite similar catecholamine levels, preterm piglets had higher angiotensin II and no cortisol increase in response to hypoxia.
- Prenatal glucocorticoid exposure altered the angiotensin II to angiotensin-(1-7) ratio.
Conclusions:
- Preterm piglets possess immature physiological responses to hypoxic stress, characterized by reduced vasoconstriction.
- This immaturity is not due to a deficit in circulating catecholamines.
- The vasodilator actions of angiotensin II may contribute to reduced vasoconstriction in preterm piglets.
- Prenatal glucocorticoids might further inhibit vasoconstriction through increased conversion of angiotensin II to angiotensin-(1-7).
Abstract:
Endocrine control of cardiovascular function is probably immature in the preterm infant; thus, it may contribute to the relative ineffectiveness of current adrenergic treatments for preterm cardiovascular compromise. This study aimed to determine the cardiovascular and hormonal responses to stress in the preterm piglet. Piglets were delivered by cesarean section either preterm (97 of 115 days) or at term (113 days). An additional group of preterm piglets received maternal glucocorticoids as used clinically. Piglets were sedated and underwent hypoxia (4% FiO2 for 20 min) to stimulate a cardiovascular response. Arterial blood pressure, skin blood flow, heart rate and plasma levels of epinephrine, norepinephrine, angiotensin II (Ang II), angiotensin-(1-7) (Ang-(1-7)), and cortisol were measured. Term piglets responded to hypoxia with vasoconstriction; preterm piglets had a lesser response. Preterm piglets had lower blood pressures throughout, with a delayed blood pressure response to the hypoxic stress compared with term piglets. This immature response occurred despite similar high levels of circulating catecholamines, and higher levels of Ang II compared with term animals. Prenatal exposure to glucocorticoids increased the ratio of Ang-(1-7):Ang II. Preterm piglets, in contrast to term piglets, had no increase in cortisol levels in response to hypoxia. Preterm piglets have immature physiological responses to a hypoxic stress but no deficit of circulating catecholamines. Reduced vasoconstriction in preterm piglets could result from vasodilator actions of Ang II. In glucocorticoid exposed preterm piglets, further inhibition of vasoconstriction may occur because of an increased conversion of Ang II to Ang-(1-7).
