Abstract
The ability of the newborn kidney to reabsorp filtered bicarbonate seems to be limited when compared to that of the adult kidney. This may be due to renal or extrarenal factors which are still ill-defined. Bicarbonate handling during acute acid-base changes was studied in newborn rabbits before the end of nephrogenesis. Fourty anesthetized mechanically-ventilated rabbits aged 5-12 days were studied during hypercapnic acidosis, metabolic acidosis or metabolic alkalosis. Inulin was used as a marker of glomerular filtration rate. Control newborn rabbits were in a state of hypochloremic metabolic alkalosis (blood pH 7.49, HCO3 31 mmol/l, Cl 83 mmol/l) which was not present in adult rabbits (pH 7.41, HCO3 19.5, Cl 100). This was ascribed to elevated urinary chloride losses in the first weeks of life. Hypercapnia with a PaCO2 of 80-100 mm Hg induced a significant rise in bicarbonate reabsorption, resulting in a possitive correlation between bicarbonate reabsorption and PaCO2 (y= 20.4 + 0.15 x, r= 0.86, p<0.01). During metabolic acidosis induced by infusing NH4Cl and metabolic alkalosis induced by infusing NaHCO3, bicarbonate reabsorption was mainly dependent on the filtered bicarbonate load in a wide range of serum bicarbonate levels (from 19 to 39 mmol/L). We conclude that in the chloride losing alkalemic newborn rabbit, bicarbonate renal handling responds to the same physiologic variables as present in adult animals.
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Heijden, A., Guignard, J. & Gautier, E. 143 THE INFLUENCE OF ACUTE ACID-BASE CHANGES ON BICARBONATE HANDLING IN TJE NEWBORN RABBIT. Pediatr Res 20, 1058 (1986). https://doi.org/10.1203/00006450-198610000-00198
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DOI: https://doi.org/10.1203/00006450-198610000-00198