Direct measurement of intracellular pressure.

The feasibility of using the servo-null technique for direct measurement of intracellular pressure (Pin) was investigated. A large cell, the Xenopus laevis oocyte, was chosen for study, and it was established that Pin obtained with this method was both stable and accurate in these cells. Median resting Pin in oocytes was found to be 0.27 cmH2O, range 0.14-0.61 cmH2O. During osmotic swelling Pin increased, in a non-linear fashion, to a value of 4.11 cmH2O, range 2.61-8.91 cmH2O, with increases in cell volume (Vc) of 24 +/- 3% (SE). This technique may be of use in the study of cellular mechanics.