Measurement of intracellular pH of bullfrog skeletal muscle and renal tubular cells with double-barreled antimony microelectrodes.

A pencil-type antimony microelectrode of double-barreled design with a tip of less than 1 to 2 microns in outside diameter was constructed and used to measure intracellular pH(pHi) on frog sartorius muscle and renal tubular cells. Simultaneous observations of membrane potential difference (EM) were made. The results obtained were as follows: (1) The in vivo pHi of frog sartorius muscle was 7.12 +/- 0.07 (SD) (n = 144); the simultaneously measured EM was -51.1 +/- 7.9 mV. The in vivo pHi of frog proximal tubule was 7.49 +/- 0.07 (n = 221) and the EM Peri across the peritubular membrane was -50.2 +/- 9.0 mV. (2) In proximal tubule in vivo, there was a negative correlation between pHi and EM (r = -.62, p < .05). On the other hand, in sartorius muscle in vivo, a positive correlation between the two was found (r = .85, p < .001). (3) In in vitro sartorius muscle, the pHi was 7.03 +/- 0.14 (n = 9) and EM was -62.4 +/- 4.4 mV within one hour after isolation. (4) Increasing the external potassium concentration in the preparations to 75 mM caused a progressive depolarization by 43.3 +/- 15.9 (m = 4) mV, while pHi changed in the alkaline direction by 0.22 +/- 0.03 pH unit. (5) These results indicate that the pHi in both tissues does not obey the Donnan rule.