EFFECT OF AMINO-ACID INFUSION ON THE VENTILATORY RESPONSE TO HYPOXIA IN PROTEIN-DEPRIVED NEONATAL PIGLETS

Several amino acids (AA) act as neurotransmitters and mediate the vent ilatory response to carbon dioxide and hypoxia in adult human beings a nd animals. To evaluate the influence of AA on the neonatal ventilator y response to hypoxia, 29 newborn piglets less than 5 d old were rando mly assigned to a control diet or protein-free diet for 7-10 d. Minute ventilation, arterial blood pressure, oxygen consumption, and arteria l blood gases were measured in sedated, spontaneous breathing piglets while they breathed room air and at 1, 5 and 10 min of hypoxia (fracti on of inspired oxygen concentration - 0.10) before and after 4 h of AA (Trophamine, 3 g/kg, i.v.) or 10% dextrose infusion. The administrati on of AA solution in protein-deprived piglets resulted in a significan t increase in minute ventilation after 10 min of hypoxia (26 +/- 19%) in comparison with their ventilatory response before AA infusion (10 /- 12%; p < 0.02). Similar increase in the ventilatory response to hyp oxia was observed in the control diet group after AA infusion (23 +/- 17% versus 11 +/- 11%; p < 0.05). Changes in arterial blood pressure, oxygen consumption, and arterial blood gases during hypoxia were simil ar before and after AA infusion. The ventilatory response to hypoxia i n both protein-free and control diet animals were similar before and a fter the 10% dextrose infusion. These results stress the importance of nutritional factors in the neonatal control of breathing.