Cytoplasmic Ca2+ at low submicromolar concentration stimulates mitochondrial metabolism in rat luteal cells.
The cytoplasmic Ca2+ signal is transferred to the mitochondrial matrix and activates mitochondrial dehydrogenases. The requirement for supramicromolar cytoplasmic [Ca2+] ([Ca2+]i) in perimitochondrial microdomains in this response has been suggested. We studied the correlation between [Ca2+]i, mitochondrial [Ca2+] ([Ca2+]m) and mitochondrial formation of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] in the presence of submicromolar [Ca2+]i in cultured rat "large" luteal cells. [Ca2+]i was monitored fluorimetrically with fura-PE3, [Ca2+]m with rhod-2 and NAD(P)H with autofluorescence. In intact cells, prostaglandin F2alpha, which induces both intracellular Ca2+ release and Ca2+ entry, stimulated mitochondrial NAD(P)H formation. Thapsigargin-induced Ca2+ release and subsequent capacitative Ca2+ entry, both resulting in Ca2+ responses not exceeding 150-200 nM, also enhanced the reduction of pyridine nucleotides. As shown in inhibitor studies, the increased steady-state NAD(P)H level was due to activation of Ca2+-dependent dehydrogenases. [Ca2+]m, measured in permeabilized cells, increased moderately, but significantly, following elevation of [Ca2+]i from 50 to 180 nM, showed a further gradual increase at higher submicromolar [Ca2+]i values and rose steeply at supramicromolar [Ca2+]i. In summary, our results demonstrate that, in a steroid-producing cell type, net mitochondrial Ca2+ uptake and mitochondrial dehydrogenation can be activated even by low submicromolar increases of [Ca2+]i.
Szabadkai
G
G
Department of Physiology, Semmelweis University, Faculty of Medicine, Budapest, Hungary.
Pitter
J G
JG
Spät
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000166:cytology / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008928:Mitochondria / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010120:Oxytocics / Q000494:pharmacology; D011555:Pseudopregnancy / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012402:Rotenone / Q000494:pharmacology; D013268:Stimulation, Chemical; D019284:Thapsigargin / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D010120:Oxytocics; D014475:Uncoupling Agents; D012402:Rotenone; D009249:NADP; D019284:Thapsigargin; D015237:Dinoprost; D002118:Calcium