Renal Aspects of Acid‐Base Control in the Newly Born III. Response to Acidifying Drugs

Summary 1. When a solution of sodium and potassium phosphates at pH 7.4 were administered to normal breast‐fed infants aged 5, 6 and 7 days, they excreted considerably more H ions (in the form of titratable acid). 2. After the administration of a single dose of an acidifying drug normal breastfed infants 7 days old (a) raised the [H+] × 10‐7 of their urine less rapidly and completely than adults, (b) excreted less of the H ions generated by the drugs but (c) excreted almost as much ammonia/kg of body weight. 3. The administration of neutral phosphates to adults (a) made no difference to the rate and extent of the rise of [H+] × 10‐7 after ammonium chloride, (b) increased the excretion of H ions in the form of titratable acid without reducing the excretion of ammonium ions. After giving phosphates to the infants they (a) maintained the [H+] × 10‐7 of the urine at a lower level, (b) increased the excretion of free H ions but (c) reduced the excretion of ammonia and consequently (d) did not increase the excretion of free H ions + ammonia so much as adults. 4. The normal breast‐fed infant appears to be handicapped in dealing with a sudden acidosis by (a) an inability to raise the [H+] × 10‐7 of the urine rapidly and completely, (b) an absence of urinary buffers, (c) an overall failure to excrete H ions so rapidly as adults. This may amount to a general deficiency on the part of the kidney to produce the necessary H ions to be excreted.