Tissue and Serum Insulin-like Growth Factor I (IGF I) Concentrations in Rats Subjected to Temporary Protein-energy Malnutrition Early in Life

Abstract

Rats subjected to temporary protein-energy malnutrition and subsequent nutritional rehabilitation remain smaller than adequatly fed animals, have a subnormal insulin secretion and persisting cellular hypoplasia in several tissues. This investigation studies whether impaired production of insulin-like growth factor I (IGF I) is another persisting consequence of malnutrition. Rats were subjected to severe protein-energy malnutrition between 3 and 6 weeks of age and subsequently fed adequate diet up to 12 weeks of age. Serum and tissue samples for analysis of IGF I were obtained at 12 weeks of age. IGF I concentrations were similar in serum, heart, liver and lung of previously malnourished and control rats. In the kidneys of previously-malnourished rats the IGF I concentration was twice that of control rats. Results suggest that during protein-energy malnutrition and subsequent nutritional rehabilitation IGF I tissue concentrations are primarily regulated by the prevailing plane of nutrition. It is speculated that the temporary protein-energy malnutrition blunts the cellular capacity for IGF I production and, except in the kidney, prevents increased IGF I tissue concentrations and associated compensatory growth.