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Effects of intrafetal IGF-I on growth of cardiac myocytes in late-gestation fetal sheep
journal contribution
posted on 2009-03-01, 00:00 authored by Eugenie R Lumbers, Min Young Kim, Judith H Burrell, Vasumathy Kumarasamy, Amanda C Boyce, Karen J Gibson, Kathryn L Gatford, Julie OwensIntrafetal insulin-like growth factor (IGF)-I promotes cardiac hypertrophy in the late-gestation fetal sheep; whether these effects are sustained is unknown. IGF-I was infused for 4 days at 80 microg/h from 121 to 125 days of gestation, and its effects at 128 days, 3 days after the infusion stopped, were determined by comparison with untreated fetal sheep. After IGF-I treatment, fetal weights were similar to those in control fetuses but kidney weights were bigger (P < 0.05), as were spleen weights of male fetuses (P < 0.05). Cardiac myocytes were larger in female than male fetal sheep (P < 0.001). IGF-I increased male (P < 0.001) but not female myocyte volumes. IGF-I did not alter the proportions of uni- or binucleated right or left ventricular myocytes. Female fetal sheep had a greater proportion of binucleated cardiac myocytes than males (P < 0.05). IGF-I-treated fetuses had a slightly greater proportion of right ventricular nuclei in cell cycle phase G(2)/M and a reduced proportion of G(0)/G(1) phase nuclei (P < 0.1). Therefore, evidence for IGF-I-stimulated cardiac cell hyperplasia in fetal sheep in late gestation was limited. In conclusion, the greater sizes and larger proportion of binucleated cardiac myocytes in female fetal sheep suggest that myocyte maturation may occur earlier in females than in males. This may explain in part the male sex-specific responsiveness of cardiac hypertrophy to IGF-I in late gestation. If IGF-I-stimulated cardiomyocyte growth is accompanied by maturation of contractile function, IGF-I may be a potential therapeutic agent for maintaining cardiac output in preterm males.
History
Journal
Am J Physiol Endocrinol MetabVolume
296Issue
3Pagination
E513 - E519Publisher
American Physiological SocietyLocation
Bethesda, Md.Publisher DOI
ISSN
0193-1849Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2009, the American Physiological SocietyUsage metrics
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No categories selectedKeywords
AnimalsBlood PressureBody WeightCarbon DioxideCardiac OutputCell CycleFemaleGestational AgeHeartHeart RateHydrogen-Ion ConcentrationInsulin-Like Growth Factor IKidneyMaleMyocytes, CardiacOrgan SizeOxygenPregnancySex CharacteristicsSheepSpleenScience & TechnologyLife Sciences & BiomedicineEndocrinology & MetabolismPhysiologyinsulin-like growth factor-IhypertrophysexNEONATAL-RATRENAL-FUNCTIONPROLIFERATIONSECRETIONINDEX
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