Developmental changes in rat adrenocortical cell membrane potential

Resting membrane potentials of zona fasciculata-reticularis cells of the rat adrenal gland varied with age. The mean membrane potentials of newborn rat adrenal cells was -56.4 +/- 0.7 mV in the first week of life. The mean potential increased slightly to -61.9 +/- 0.8 mV in the second week and then decreased with age to a mean of -38.5 +/- 0.8 mV in 25--50 week old rats and of -25.9 +/- 1.9 mV in 100 week old rats. The changes in membrane potential may correlate with the indices of adrenocortical growth and activity.