UEDA, H.
Relation between Urinary Bicarbonate Concentration and Carbon Dioxide Tension in Patients with Proximal or Distal Renal Tubular Acidosis. Tohoku J. exp. Med., 1981,
133 (1), 21-32 The relation of urinary bicarbonate concentration (U
HCO3-) to the difference between urinary pCO
2 and arterial blood pCO
2 (U-BpCO
2) has not yet been clearly elucidated either in normal subjects or in patients with distal renal tubular acidosis (distal RTA). Nor are there any reports dealing with the relation between U
HCO3- and U-BpCO
2 in patients with hypokalemia or with proximal renal tubular acidosis (proximal RTA). In the present study, with the objective of analyzing the differences in the production of urinary pCO
2 in different groups of patients with hypokalemia, those with distal RTA and those with proximal RTA, we loaded these patients and control subjects with sodium bicarbonate, and studied the changes in the relations between U
HCO3- and U-BpCO
2. The following results were obtained: (1) (a)
When UHCO3- was higher than 130mEq/liter: Normal subjects had a positive correlation between U
HCO3- and U-BpCO
2 (
p<0.001). In the patients with hypokalemia and distal RTA, U-BpCO
2 tended to show lower levels than in the control subjects when compared on the same level of U
HCO3-. In the patient with proximal RTA, U-BpCO
2 was higher than that in the control when compared on the same level of U
HCO3- (
p<0.001). (b)
When UHCO3- was lower than 130mEq/liter: Normal subjects showed no correlation between U
HCO3- and U-BpCO
2 (
p>0.7). In the patients with distal RTA, U-BpCO
2 was lower than that in the control (
p<0.005). (2) In the patients with hypokalemia, after the loading of potassium chloride, U-BpCO
2 tended to rise compared on the same level of U
HCO3-. (3) In the control subjects loaded with a large dose of phosphate, the values of U-BpCO
2 compared on the same levelof U
HCO3- were not distinctive compared with those in other control subjects, when U
HCO3- was over 130mEq/liter. These results suggest that in the patient with proximal RTA, an increase in bicarbonate load in the distal tubule is likely to augment the formation of carbonic acid, raising the value of U-BpCO
2. The fact that in the patients with distal RTA U-BpCO
2 was lower than that in the control subjects seems to be attributed not only to the low value of U
HCO3- due to potassium deficiency but also to the impairment of secretion of hydrogen ion in the distal tubule.
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