Treatment with the aminoglycoside antibiotic gentamicin can be associated with severe adverse effects, including renal Ca²⁺ wasting. The underlying mechanism is unknown but it has been proposed to involve activation of the Ca²⁺-sensing receptor (CaSR) in the thick ascending limb, which would increase expression of claudin-14 (CLDN14) and limit Ca²⁺ reabsorption. However, no direct evidence for this hypothesis has been presented.

We studied the effect of gentamicin in vivo using mouse models with impaired Ca²⁺ reabsorption in the proximal tubule and the thick ascending limb. We used a Cldn14 promoter luciferase reporter assay to study CaSR activation and investigated the effect of gentamicin on activity of the distal nephron Ca²⁺ channel transient receptor potential vanilloid 5 (TRPV5), as determined by patch clamp in HEK293 cells.

Gentamicin increased urinary Ca²⁺ excretion in wild-type mice after acute and chronic administration. This calciuretic effect was unaltered in mice with genetic CaSR overactivation and was present in furosemide-treated animals, whereas the calciuretic effect in Cldn14^–/– mice and mice with impaired proximal tubular Ca²⁺ reabsorption (claudin-2 [CLDN2]-deficient Cldn2^–/– mice) was equivalent to that of wild-type mice. In vitro, gentamicin failed to activate the CaSR. In contrast, patch clamp analysis revealed that gentamicin strongly inhibited rabbit and human TRPV5 activity and chronic gentamicin administration downregulated distal nephron Ca²⁺ transporters.

Gentamicin does not cause hypercalciuria via activation of the CaSR-CLDN14 pathway or by interfering with proximal tubular CLDN2-dependent Ca²⁺ reabsorption. Instead, gentamicin blocks distal Ca²⁺ reabsorption by direct inhibition of the Ca²⁺ channel TRPV5. These findings offer new insights into Ca²⁺ wasting in patients treated with gentamicin.

用氨基糖苷类抗生素庆大霉素治疗可能与严重的副作用相关，包括肾 Ca ²⁺消耗。潜在的机制尚不清楚，但已提出涉及厚升肢中Ca ^{2+感应受体 (CaSR) 的激活，这将增加 claudin-14 (CLDN14) 的表达并限制 Ca 2+}重吸收。然而，没有提出这一假设的直接证据。

我们使用近端小管和粗升肢Ca ^{2+重吸收受损的小鼠模型研究了庆大霉素}在体内的作用。我们使用Cldn14启动子荧光素酶报告基因测定来研究 CaSR 激活，并研究庆大霉素对远端肾单位 Ca ²⁺通道瞬时受体电位香草素 5 (TRPV5)活性的影响，这是通过膜片钳在 HEK293 细胞中确定的。

庆大霉素在急性和慢性给药后增加了野生型小鼠的尿 Ca ^2+排泄。这种钙尿作用在具有遗传 CaSR 过度激活的小鼠中没有改变，并且存在于呋塞米处理的动物中，而钙尿作用在Cldn14 ^{–/–小鼠和近端肾小管 Ca 2+}重吸收受损的小鼠（claudin-2 [CLDN2]-缺陷Cldn2 ^–/–小鼠）相当于野生型小鼠。在体外，庆大霉素未能激活 CaSR。相比之下，膜片钳分析显示庆大霉素强烈抑制兔和人 TRPV5 活性，慢性庆大霉素给药下调远端肾单位 Ca ²⁺转运商。

Gentamicin 不会通过激活 CaSR-CLDN14 通路或通过干扰近端肾小管 CLDN2 依赖性 Ca ²⁺重吸收而引起高钙尿症。相反，庆大霉素通过直接抑制Ca ^{2+通道 TRPV5 来阻断远端 Ca 2+}重吸收。这些发现为接受庆大霉素治疗的患者的Ca ^{2+消耗提供了新的见解。}