Bartter syndrome 裡，macula densa 為什麼讓 renin 失控？
核心邏輯：TAL 的 NKCC2 / ROMK / ClC-Kb loss-of-function 讓 macula densa 看到「假性低 Cl⁻」，
觸發 COX2-PGE2 pathway，刺激 JG cell renin release。NSAID 阻斷 COX2 後，PGE2 與 renin 都下降。
Core logic: Bartter defects lower macula-densa intracellular chloride, exaggerate COX2 and PGE2, then drive renin despite volume and electrolyte consequences.
3D TGF Simulator
Mechanism Chain
NKCC2 absorbs Na⁺-K⁺-2Cl⁻ in thick ascending limb.
緻密斑細胞內 Cl⁻ 不低，TGF 判讀正常。
只維持 basal prostaglandin tone.
RAAS 不被錯誤放大。
TAL cannot reclaim Cl⁻ effectively.
緻密斑誤判成 tubule salt delivery 太低。
PGE2 signal rises sharply.
Secondary hyperaldosteronism drives hypokalemic metabolic alkalosis.
Indomethacin-like effect lowers prostaglandin synthesis.
MD-to-JG paracrine drive weakens.
RAAS amplification is dampened.
血鉀與鹼中毒通常改善，但仍需監測腎功能與 GI risk。
Particle Encoding
Green Cl⁻ particles travel through TAL toward macula densa. Bartter reduces effective uptake, so the macula densa cluster receives a low-Cl⁻ signal.
Amber particles radiate from macula densa toward JG cells. Bartter increases emission; NSAID suppresses it despite persistent transporter loss.
Red particles leave JG granules into the afferent arteriole. Emission follows PGE2-mediated stimulation of juxtaglomerular cells.
Board-Style Takeaway
臨床連結：Bartter 不是「真正身體想要 renin 高」，而是 TAL salt handling failure 讓 macula densa 用錯誤的 Cl⁻ 訊號啟動 renin pathway。
Clinical link: The pathway explains why prostaglandin inhibition can be therapeutic: it targets the COX2-PGE2 bridge between low macula-densa chloride and JG renin secretion.
This visualization is for teaching physiology and should not replace patient-specific dosing, renal monitoring, or risk assessment.