PMCA density in bullfrog hair cell stereocilia quantified by immunogold EM and electrogenic pump current measurement. PMCA is the primary Ca2+ extrusion mechanism; blocking it with vanadate or carboxyeosin raises bundle [Ca2+] substantially. This is the correct citation for PMCA’s role in stereocilia Ca2+ clearance — the “Mammano 1999 Pflugers Arch” attribution in the h05 scripts is wrong; that paper (PMID 10436049) concerns ATP-evoked IP3-gated Ca2+ release, not PMCA kinetics.
Key finding
~10^6 PMCA molecules per hair bundle (~2000/µm² of membrane). Pharmacological block shows PMCA is essential for maintaining low resting [Ca2+] in stereocilia. Does not report a simple first-order k_extrusion — for a rate constant, use Beurg et al. 2010 J Neurophysiol (PMID 20427623).
Numbers that matter
| Parameter | Value | Units | Conditions | Notes |
|---|---|---|---|---|
| PMCA density in stereocilia | ~2000 | pumps/µm² | Bullfrog sacculus, immunogold | ~10^6 total per bundle |
| PMCA necessity | confirmed | — | Vanadate/carboxyeosin block | Functional evidence; kinetics not quantified |
| First-order k_extrusion | NOT GIVEN | — | — | Use Beurg 2010 for rate constant estimate |
Limitations
- Bullfrog sacculus, not mammalian OHC. PMCA2 density in mammalian OHC is higher.
- Does not report turnover rate or first-order extrusion rate constant.
- For k_extrusion ~30 /s in h05 scripts, cite Beurg 2010 (PMID 20427623) instead.
Connections
[source]calcium-oscillation — corrects misattribution of k_extrusion to “Mammano 1999 Pflugers Arch”[see-also]2010-beurg-calcium-balance-ohc — provides quantitative k_extrusion[applies]STRC Calcium Oscillation Acoustic Therapy