Influence of parathormone on renal transport of amino acids in children

Abstract

With the permission of their parents 24 newborn babies of varying weights and gestational ages have been studied with respect to their urinary excretion of calcium and phosphorus. Timed specimens of urine were collected as continuously as possible during the first 3 days and on the 7th day of life; venous specimens of blood were also obtained on each of these days. Calcium, phosphorus, sodium and creatinine measurements were performed on these specimens. It was found that both sodium and calcium excretion followed a similar course with high lwels of excretion soon after birth falling during the first 3 days and rising by the end of the first week. There were no statistically significant differences between groups of babies classed as pre-term, small for dates or mature. Serum calcium lwels fell during this week while phosphorus lwels rose. Urinary phosphorus excretion was low soon after birth but rose rapidly until by the end of the week phosphorus excretion seemed considerably to exceed phosphorus filtration. Assuming that creatinine handling by the kidney of the newborn is similar to that of older infants and that creatinine clearance'represents an approximation to glomerular filtration, these infants (fed on artificial phosphate rich diet)clearly ingest a gross excess of phosphate and seem able actually to secrete phosphorus into their renal tubules in an attempt to remove it.