?Calcium metabolism in intact isolated thymocytes?

Abstract

Isolated rat thymocytes incubated under proper metabolic conditions extrude Ca²⁴ previously taken up under metabolically unfavourable conditions. The extrusion can be supported by both respiratory and glycolytic energy but glycolysis seems to be more efficient for this purpose. La³⁻ (50–200 μM) and the ionophore A 23187 inhibit cell Ca²⁺ extrusion. Ruthenium Red (1–100 μM)) does not influence cell Ca²⁺ extrusion while it inhibits the in situ mitochondrial cation uptake. All the results are consistent with a cell regulation model of Ca ²⁺ content in which both plasma membrane and mitochondria co-operate, acting in opposite directions, in order to decrease cytosolic Ca ²⁺ concentration. The possibility of Na⁺-Ca²⁺ hetero-exchange participation to cell Ca²⁺ homeostasis regulation is also discussed.