Finding. Human sperm load mitochondria with CatSper calcium when they capacitate, and that load is how they start to swim in the hyperactivated style. Irigoyen, Santi and colleagues take paired samples from normozoospermic donors, before and after capacitation. Respiratory control ratio, coupling efficiency, membrane potential, and mitochondrial calcium all rise. The calcium rise dies if you remove extracellular calcium, block CatSper, or block the mitochondrial calcium uniporter. The same two blocks blunt the membrane-potential rise and cut hyperactivated motility. Progressive motility and total motility stay up. Poison the mitochondrion and hyperactivation falls; the acrosome reaction does not. The mouse path is conserved.
Why this paper matters
Capacitation has been two posters on one wall: CatSper and mitochondria. This preprint draws the arrow. For clinics it says hyperactivation, not the acrosome, is the mitochondrial readout. For contraception or fertility rescue it names MCU as a second handle next to CatSper.
What they actually measured
Paired human donors, four mitochondrial assays, two channel inhibitors, motility classes, acrosome. No IVF dish.
How to read the score
Mid 80s. Human, paired, conserved mechanism, clean motility split. Confidence is high for the pharmacology.
Caveats
Drugs, not mutants. Fertile donors. No oocyte.
What to do with it
If you score human capacitation, add mitochondrial calcium and RCR next to hyperactivation. If you drug CatSper, expect MCU and membrane potential to follow. Do not treat MCU inhibitors as a proven contraceptive from this brief.