AJP - Endocrinology and Metabolism, Vol 266, Issue 5 E739-E749, Copyright © 1994 by American Physiological Society
Continuous on-line hydrogen ion monitoring to study flow dynamics of perifusion systems and cellular metabolism
R. M. Brand, M. N. Ghazzi, A. Rolfes-Curl, H. C. Cantor and A. R. Midgley
Reproductive Sciences Program, University of Michigan, Ann Arbor 48109-0404.
Time-dependent concentration profiles of input signals and feedback of
metabolic products can strongly influence cellular responsiveness. To study
these parameters, we developed a perifusion system that can deliver
biological signals to cells with minimal dispersion, monitor real time
responses, and remove waste products continuously. By monitoring pH with
miniature hydrogen ion-selective electrodes at intervals of 1 s, effects of
dispersion, flow rate, pumping system, and changes in cellular metabolism
were demonstrated. Dynamic responses of a human cell line to a series of
10-min pulses of the metabolic uncoupler carbonyl cyanide
m-chlorophenylhydrazone (CCCP) were monitored. A rapid 1-min increase in
acid release occurred on exposure to CCCP, followed by a decrease in
acidification and then a gradual return to a baseline slightly more acidic
than before administration of CCCP. These observations demonstrate that
this perifusion system can reveal small changes in pH (+/- 0.0005 units)
induced by metabolic perturbations and has the potential to reveal the
dynamics of cellular responsiveness to a wide range of hormonal, metabolic,
and other chemical signals.
