[Experimental model for long-term trials of parenteral nutrition in the growing rat].

Young male Sprague-Dawley rats (weighing approximately 170 gs) are entirely maintained by parenteral nutrition over a period of 4 weeks. The nutrient solution - a mixture of amino acids, glucose, fat, electrolytes, vitamins, and trace elements in a composition optimal for rats - is infused by means of a roller pump through a catheter leading to the vena cava and having its outlet in the midscapular region. The animals are provided with a little harness and kept in metabolic cages. They are freely movable during the entire infusion period. The average weight gain with an energy supply of 350 kcal and 1 g N/kg/24 h was recorded to be 3.8g/day. Since the requirement of nitrogen and energy per unit of body weight decreases with growth, nitrogen balance becomes increasingly positive in the course of the experimental period. Cumulative nitrogen retention during 24 days was 4.23 g. Operation techniques, treatment of the animals and composition of the infusion solutions are described in detail.