Measurement of Intracellular pH of Bullfrog Skeletal Muscle and Renal Tubular Cells with Double-Barreled Antimony Microelectrodes

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Abstract
A pencil-type Sb microelectrode of double-barreled design with a tip of < 1 to 2 .mu.m 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 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. In proximal tubule in vivo, there was a negative correlation between pHi and EM (r = -0.62, P < 0.05). In sartorius muscle in vivo, a positive correlation between the 2 was found (r = 0.85, P < 0.001). In in vitro sartorius muscle, the pHi was 7.03 .+-. 0.14 (n = 9) and EM was -62.4 .+-. 4.4 mV within 1 h after isolation. Increasing the external K 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. The pHi in both tissues does not obey the Donnan rule.