Program project support is requested for a coordinated, multidisciplinary approach to investigate the role of milk-borne hormones and other active biological substances for the neonate. Support is requested for scientific projects and three cores (Morphological, Animal and Administrative). Three projects deal with the fate and effects of milk-borne peptide hormones in the suckling rats (Project #1. Role of Milk-Borne Somatostatin, PI: O. Koldovsky; Project #2. Metabolism of Milk-Borne Peptides, PI: T.P. Davis; and Project #5. Role of Nutrition and Milk-Borne Insulin-Like Growth Factors, PI: A.F. Philipps). These studied peptide hormones have important regulatory functions and may individually or collectively modulate the sensitivity of the developing gastrointestinal tract to necrotizing enterocolitis. Project #3. Role of Milk-Borne Carnitine, PI: C.A. Flores, deals with the role of milk-borne carnitine, an important factor in fat metabolism. Project #4. Role of Milk-Borne Biological Substances, PI: R. McCuskey, evaluates the role of these substances on the development of specific liver functions. These projects are supported by the three cores. The proposed studies are basic in nature, and the information derived will be applicable to a variety of normal and pathological conditions. Studies have demonstrated that some of these substances are absent in infant formulas, but present in human breast milk, emphasizing the significance of the proposed studies.