Acid phosphatase activity and the state of lysosomal membranes in a primary culture of cardiomyocytes of newborn rats during hypoxia

: Acid phosphatase activity, ATP and cyclic nucleotide levels were studied in primary cardiomyocyte cultures of newborn rats under hypoxic conditions. It was shown that incubation of cardiac cells in Eagle's medium supplemented with 10% calf serum during hypoxia (5% O2, 5% CO2, 90% N2) caused an hour later a decrease in lysosomal acid phosphatase activity, whereas free enzyme activity increased. The exposure of cells in Hanks salt solution to one hour hypoxia resulted in a 3-fold decrease of ATP level and further increase in free acid phosphatase activity. It was found that cAMP and cGMP levels do not depend on the presence of hypoxia. The mechanisms involved in the regulation of lysosomal membrane state are discussed.