Urinary calcium and net acid excretion as well as the acid-base parameters of the blood were determined before and after a NH4Cl load applied in a single dose of 2.8 mEq/kg body weight. In order to assess the effect of maturity and postnatal development, a study was made on 47 newborn infants with a birth weight of 1000-4380 g on the 7th day, and 11 prematures with a birth weight of 1000-1970 g, weekly for 6 consecutive weeks. The results were compared to those for infants of 3-11 months of age. At one week of age, NH4Cl ingestion resulted in a significantly greater increase of metabolic acidosis in infants with a birth weight under 2000 g than in the larger ones. With increasing postnatal age the metabolic acidosis of premature infants increased to about the same extent in response to NH4Cl load irrespective of the pre-loading level of acidosis or postnatal age. Both the urinary NAE and UCaE of one week-old infants increased markedly with increasing birth weight and they were invariably augmented by the acid load. NH4Cl-induced NAE and UCaE were significantly higher in infants with a birth weight over 2500 g than in their smaller matches (p < 0.025). In prematures, in spite of the postnatal development of renal capacity to excrete hydrogen ions, the NH4Cl-induced UCaE remained unchanged, or expressed in per cents of the pre-loading level even a slight, statistically not significant decrease could be observed during the first six weeks of life. It is suggested that the skeletal buffering measured as NH4Cl-induced urinary calcium loss, may be an important defence mechanism against acidosis already in the early period of life. Low-birth-weight prematures are, however, compromised in face of an acid load by the limited buffer function of the bones.
|Number of pages||10|
|Journal||Acta paediatrica Academiae Scientiarum Hungaricae|
|Publication status||Published - Jan 1 1977|
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