Measurements of the Intracellular Ph in a Single Cell of Nitella Flexilis by Means of Micro-glass Ph Electrodes.

The use of micro-glass electrodes sensitive to the activity of selected cations has permitted a direct measurement of intracellular ionic activity , e. g., the activity of hydrogen ion in a single crab muscle fiber (CALDWELL 1954), and in a single squid giant axon (CALDWELL 1958, SPYROPOULOS 1960), the activity of sodium and potassium ion in a single squid giant axon (HINKE 1960). With a micro-glass electrode of the size smaller than 1 micron at the tip and 50-60 micra in length, SOROKINA and KOSTYK (1959) successfully measured the intracellular pH in a single fiber of frog's sartorius muscle. The authors have recently measured the pH of the sap of a single internodal cell of the fresh water alga, Nitella flexilis, by means of a micro-glass pH electrode of the size 60-80 micra in diameter. It was found that this relatively large electrode gave stable pH recordings over a period of at least 30 minutes, with fluctuations of less than 2 mV after it was inserted into the vacuolar sap axially through a freshly cut end.