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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 Owens
Intrafetal 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 Metab

Volume

296

Issue

3

Pagination

E513 - E519

Publisher

American Physiological Society

Location

Bethesda, Md.

ISSN

0193-1849

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2009, the American Physiological Society