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Sensitivity of organ growth to chronically low oxygen levels during incubation in Red Junglefowl and domesticated chicken breeds
Linköping University, Department of Physics, Chemistry and Biology, Zoology . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Zoology . Linköping University, The Institute of Technology.
2011 (English)In: Poultry Science, ISSN 0032-5791, Vol. 90, no 1, 126-135 p.Article in journal (Refereed) Published
Abstract [en]

Genetic selection programs have imposed large phenotypic changes in domesticated chicken breeds that are also apparent during embryonic development. Broilers, for example, have a faster growth rate before hatching in comparison with White Leghorns, indicating that the allocation of resources toward different functions already begins before hatching. Therefore, we hypothesized that embryonic organ growth would follow different developmental trajectories and would be differentially affected by an oxygen shortage during incubation. Heart, brain, and liver growth were studied in broiler, White Leghorn, and Red Junglefowl embryos at embryonic (E) ages E11, E13, E15, E18, and E20, and the results were fitted to growth allometric equations to determine the degree of organ stunting or sparing caused by low oxygen during incubation. Hypoxia caused a 3-fold larger mortality in Red Junglefowl than in the domesticated breeds, with a similar impairment of embryonic growth of 18%, coupled with a reduction in yolk utilization of 56%. Relative brain size was not affected by hypoxia in any breed, but a substantial stunting effect was observed for the liver and heart at late embryonic ages, with marked differences between breeds. In Red Junglefowl, only the heart was stunted. In White Leghorns, only the liver was stunted, and in broilers, both organs were stunted. These results can be explained in terms of the selection pressure on long-term production traits (reproductive effort) in White Leghorns, requiring a more efficient lipid metabolism, compared with the selection pressure on shorter-term production traits (growth) in broilers, requiring overall metabolic turnover and convective nutrient delivery to all tissues. At the same time, a remarkable sparing of the heart was observed in broilers and Red Junglefowl between E11 and E15, which suggests that cardiac growth can be manipulated during embryonic development. This result could be relevant for manipulating the phenotype of the heart for management purposes at a developmental stage when the bird is most versatile and phenotypically malleable.

Place, publisher, year, edition, pages
Poultry Science Association , 2011. Vol. 90, no 1, 126-135 p.
Keyword [en]
broiler, domestication, organ growth, hypoxia, cardiovascular development
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-64572DOI: 10.3382/ps.2010-00996ISI: 000285504700016OAI: diva2:392813
Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2011-02-04
In thesis
1. Cardiovascular beta-adrenergic signaling: Maturation and programming effects of hypoxia in a chicken model
Open this publication in new window or tab >>Cardiovascular beta-adrenergic signaling: Maturation and programming effects of hypoxia in a chicken model
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite the importance of β-adrenergic receptors (βARs) in cardiovascular disease, not much is known about how prenatal hypoxia effects βAR signaling in the postnatal animal. Thus, the aim of this thesis was to characterize the pre- and postnatal maturation of the cardiovascular βARs and the effects of chronic prenatal hypoxia on βAR signaling in the embryo and adult animal using the chicken as experimental model.

βARs belong to the seven-transmembrane receptor family of G-protein coupled receptors and are crucial for cardiovascular development, growth and regulation. In the cardiovascular system there are two dominant  subtypes, β1AR and β2AR, whose main ligands are the biogenic catecholamines epinephrine and norepinephrine. When stimulated, βARs primarily couple to the stimulatory G-protein (Gas) that stimulates adenylyl cyclase to convert ATP to cAMP. cAMP increases ino- and chronotropy of the heart and causes relaxation of blood vessels. β2ARs also have the ability to switch to inhibitory G-protein (Gi) signaling that decreases the cAMP production. To protect the cardiovascular system from overstimulation, the βARs desensitize and downregulate in the case of prolonged elevation of catecholamines. This blunts the cardiovascular response and the mechanisms behind desensitization/downregulation, including the β2AR switch to Gi signaling, are closely linked to cardiovascular disease and are of immense importance in medical therapeutics.

Hypoxic stress releases catecholamines and thereby triggers βAR responses and desensitization/downregulation mechanisms. Hypoxia quite commonly occurs in utero and it is well known that prenatal insults, like malnutrition or hypoxia, are coupled to an increased risk of developing adult cardiovascular disease. This is referred to as developmental programming and constitutes an important and modern field of research.

In this thesis, I show that; 1) the developmental trajectory for organ growth, especially the heart, is affected by hypoxia, 2) chronic prenatal hypoxia causes cardiac embryonic βAR sensitization, but causes desensitization postnatally suggesting that there is a hypoxia-induced “programming” effect on adult β-adrenoceptor function, 3) the adult βAR desensitization following prenatal hypoxia is linked to a decrease in β1AR/β2AR ratio, a decrease in cAMP following βAR stimulation with isoproterenol and an increase in Gas, 4) the chorioallantoic (CA) membrane arteries display hypoxic vasoconstriction, but lack 8-adrenergic reactivity and 5) hypotension of the chronically hypoxic chicken embryo is linked to a potent βAR relaxation of the CA vasculature and an increased AR sensitivity of the systemic arteries with no changes in heart rate.

In conclusion, chronic prenatal hypoxia causes growth restriction, re-allocation and has programming effects on the βAR system in the adult. The latter indicates that the βAR system is an important factor in studying hypoxic developmental programming of adult cardiovascular disease.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 48 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1330
National Category
Natural Sciences
urn:nbn:se:liu:diva-65367 (URN)978-91.7393-352-0 (ISBN)
Public defence
2010-09-10, Planck, Hus E, Campus Valla, Linköpings universitet, Linköping, 09:15 (English)
Available from: 2011-02-04 Created: 2011-02-04 Last updated: 2012-11-19Bibliographically approved

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