Cyclic AMP and Ca2+ uptake by mastocytoma mitochondria

A thorough re-investigation was undertaken of a variety of factors that might explain the increased uptake of 45Ca2+ by mitochondria isolated from N6, O2'-dibutyryladenosine-3',5'-cyclic monophosphate (DB cyclic AMP)--treated PY815 cells. This showed that mitochondria isolated from DB cyclic AMP treated cells take up 45Ca2+ at a 30 per cent faster rate than mitochondria from untreated cells, although both mitochondria eventually reduce the total external Ca2+ to the same levels. 45Ca2+ precharged mitochondria from DB cyclic AMP-treated cells also leaked 45Ca2+ more slowly than those from untreated cells when they were recovered by filtration. Thus an apparently greater uptake of 45Ca2+ by mitochondria from DB cyclic AMP-treated cells was a consequence of the filtration procedure. In fact, mitochondria from DB cyclic AMP-treated cells contained less total Ca2+ than those from untreated cells, while DB cyclic AMP-treated cells also contained less total Ca2+ than untreated cells. The results suggest that mitochondria do not play an important role in controlling the growth of DB cyclic AMP-treated PY815 cells through effects on cytoplasmic Ca2+ availability.