Differentiation of mouse embryonal carcinoma cells PCC4 by heat shock and the kinetics of induction of heat shock proteins.

Heat shock to embryonal carcinoma cells PCC4 at 45 degrees C for 30 min resulted in the differentiation of cells although heat shock response was induced on exposure to 42 degrees C for 60 min. Differentiated cells were large and well spread with reduced nuclear/cytoplasmic ratios as compared to undifferentiated cells. Change in cell morphology was associated with the disappearance and appearance of stage specific embryonic antigens 1 and 3 respectively. We also found a change in intracellular pH in PCC4 cells within 30 min of heat shock as measured by the change in fluorescence intensity of a probe incorporated into cells during heat shock.

Changes in cytoplasmic pH upon heat shock in embryonic and adult rat liver ceils.

All living cells, when exposed to elevated temperatures, undergo physiological changes which result in the expression of a specific set of heat shock proteins. Study of the possible physiological changes in adult and embryonic rat liver cells indicated a change in intracellular pH upon heat shock. Using 2', 7'-bis (2-carboxyethyl)-5 (and -6) carboxyfluorescein acetoxymethyl ester, we demonstrate here that the intracellular pH of adult and embryonic liver cells is different and that there is an increase in relative fluorescence intensity in both adult and embryonic cells upon heat shock, which corresponds to about 0·2 to 0·3 pH units. We also show that in addition to heat, some of the inducers of heat shock like response in many systems also induce a change in intracellular pH and induce heat shock proteins at 37°C in fetal liver cells. The possible mechanisms of induction of heat shock proteins during heat shock and in the presence of inducers at normal temperature are discussed.