Insulin-like growth factor-I stimulates erythropoiesis when administered enterallyâ–

Author： Kling Pamela J.   Taing K. Muy   Dvorak Bohuslav   Woodward Suann S.   Philipps Anthony F.  

Publisher： Informa Healthcare

ISSN： 0897-7194

Source： Growth Factors, Vol.24, Iss.3, 2006-09, pp. : 218-223

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Abstract

Background: Insulin-like growth factors I and II (IGF-I and IGF-II) are potent growth factors involved in development. IGF-I stimulates proliferation of erythropoietic progenitors and parenteral IGF-I administration stimulates in vivo erythropoiesis in animals. IGF-I and IGF-II are both present in mammalian milks and when milk-borne, are resistant to neonatal gastrointestinal degradation. Whether milk-borne IGF-I or IGF-II regulates neonatal erythropoiesis in not known. We hypothesized that physiological doses of enteral IGFs stimulate erythropoiesis in suckling rats.Methods: Eight day-old Sprague Dawley rats were artificially fed for 4 days with rat milk substitute (RMS) or RMS supplemented with physiological levels of IGF-I or IGF-II. Rats fed IGF-I and IGF-II were compared to control RMS. Blood and marrow were collected; measures of red cell mass, measures of erythropoietic stimulus, and indices of iron status were measured.Results: Rats fed IGF-I had higher hemoglobin (Hb) levels (100±Â10Âg/l), compared to those fed RMS (94±Â9) or IGF-II (91±Â6), pÂ<Â0.001. After IGF-I supplementation, red blood cell counts (RBC) (pÂ<Â0.04) and hematocrits (pÂ<Â0.002) were also higher. Plasma erythropoietin (Epo) levels, reticulocytes, plasma iron and erythrocyte iron incorporation were similar.Conclusion: Intact enteral IGF-I reaches distal erythropoietic tissue resulting in greater red cell mass, but not by increasing plasma Epo levels or by altering cellular iron transport.

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