1077 RENAL RESPONSE TO ACUTE HYPOXIA IN NEWBORN PUPPIES

Abstract

The purpose of this study was to investigate the effect of acute hypoxic hypoxia (H) on renal function in 1 wk old (N) and 6 wk old (O) puppies. Under anesthesia a tracheostomy was performed in all animals. H was induced by administering a gas mixture of 5% O₂ and 95% N₂ for 45 minutes. Measurements of arterial blood gases, glomerular filteration rate (GFR ml/min) renal blood flow (RBF), osmolar clearance (COS), fractional excretion of sodium (FE_Na), urinary flow (UV ml/min), and blood pressure (BP) were determined by standard methods, before (C) and during (H). BP, heart rate and hematocrit remained unchanged during the experiment. In N PO₂ decreased from a mean value of 75±7 to 20±4 mmHg^*, PCO₂ decreased from 35±4 to 14±1 mmHg^* and pH decreased from 7.6±0.7 to 7.26±0.12^*. Similar changes were seen in O except that the metabolic acidosis was greater than in N^*. A greater than 50% decrease in GFR was observed in both groups^*. RBF decreased 1.5-fold in N^* and 3-fold in O^*. FE_Na and UV however, increased 17^* and 6-fold^*in N , while the increase was only 1.3^* and 1.25^*-fold in O . The reasons for these differences in magnitude of renal response to hypoxia between newborns and older puppies are not clear. Elevated levels of plasma angiotensin and increased renal sensitivity to catecholamines, found in newborns may be responsible for these observed differences.

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