AJP - Renal Physiology, Vol 251, Issue 5 933-F937, Copyright © 1986 by American Physiological Society
A new microelectrode method for simultaneous measurement of pH and PCO2
K. Bomsztyk and M. B. Calalb
A liquid-membrane pH-PCO2 microelectrode is described for the simultaneous
measurement of pH and PCO2 in tissues and body fluids. The microelectrode
is simple and easy to fabricate. It can be used to measure HCO3
concentration in solutions at chemical equilibrium. In the physiological
range the microelectrode response is linear with nearly Nernstian slopes
for PCO2 (61.2 +/- 2.0 mV/log10 PCO2) and pH (63.7 +/- 1.9 mV/pH units) (n
= 14) at 37 degrees C. The PCO2 response is independent of the solutions'
pH, anionic composition, and presence of serum proteins. In randomly
micropunctured rat surface proximal tubules, pH averaged 6.80 +/- 0.04 and
PCO2 averaged 57.7 +/- 4.6 mmHg (n = 22), whereas in the adjacent
peritubular capillaries pH was higher (7.27 +/- 0.03) but PCO2 was not
different (55.7 +/- 4.6 mmHg) (n = 22). Systemic arterial PCO2 was
significantly lower compared with the renal cortex and averaged 37.4 +/-
2.4 mmHg (n = 14). Directly measured and pH-PCO2 microelectrode-derived
HCO3 concentrations in systemic arterial blood, surface fluid bathing the
kidney, and randomly micropunctured proximal tubules were approximately
equal.
