Wilson P D, Hovater J S, Casey C C, Fortenberry J A, Schwiebert E M
Department of Medicine, Mount Sinai School of Medicine, New York, New York, USA.
J Am Soc Nephrol. 1999 Feb;10(2):218-29. doi: 10.1681/ASN.V102218.
Autosomal dominant polycystic kidney disease (ADPKD) cyst enlargement is exacerbated by accumulation of fluid within the lumen of the cyst. Extracellular nucleotides and nucleosides stimulate fluid and chloride (Cl-) secretion across epithelia and are potent autocrine and paracrine agonists within tissues. This study tests the hypothesis that ATP may be released by ADPKD epithelial cells. Once released, extracellular nucleotides and their metabolites may become "trapped" in the cyst lumen. As a consequence, extracellular ATP may augment ADPKD cyst enlargement through stimulation of salt and water secretion across ADPKD epithelia that encapsulate ADPKD cysts. To test this hypothesis, bioluminescence detection assays of ATP released from primary cultures of human ADPKD epithelial cells were compared with non-ADPKD human epithelial primary cultures. ADPKD cultures release comparable or greater amounts of ATP than non-ADPKD cultures derived from proximal tubule or cortex. ATP release in both ADPKD and non-ADPKD primary epithelial monolayers was directed largely into the apical medium; however, basolateral-directed ATP release under basal and stimulated conditions was also observed. Hypotonicity potentiated ATP release into the apical and basolateral medium in a reversible manner. Reconstitution of isotonic conditions with specific osmoles or inhibition with mechanosensitive ion channel blockers dampened hypotonicity-induced ATP release. "Flash-frozen" cyst fluids from ADPKD cysts, harvested from multiple donor kidneys, were screened by luminometry. A subset of cyst fluids contained as much as 0.5 to 10 microM ATP, doses sufficient to stimulate purinergic receptors. Taken together, these results show that ADPKD and non-ADPKD human epithelial primary cultures release ATP under basal and stimulated conditions and that ATP is released in vitro and into the cyst fluid by cystic epithelial cells in concentrations sufficient to stimulate ATP receptors. It is hypothesized that extracellular nucleotide release and signaling may contribute detrimentally to the gradual expansion of cyst fluid volume that is a hallmark of ADPKD.
常染色体显性多囊肾病（ADPKD）囊肿的扩大因囊腔内液体的积聚而加剧。细胞外核苷酸和核苷可刺激上皮细胞分泌液体和氯离子（Cl-），并且是组织内强效的自分泌和旁分泌激动剂。本研究检验了一个假说，即ATP可能由ADPKD上皮细胞释放。一旦释放，细胞外核苷酸及其代谢产物可能会“被困”在囊肿腔内。因此，细胞外ATP可能通过刺激包绕ADPKD囊肿的ADPKD上皮细胞分泌盐和水，从而加剧ADPKD囊肿的扩大。为了验证这一假说，将人ADPKD上皮细胞原代培养物释放的ATP的生物发光检测分析结果与非ADPKD人上皮细胞原代培养物进行了比较。ADPKD培养物释放的ATP量与源自近端小管或皮质的非ADPKD培养物相当或更多。ADPKD和非ADPKD原代上皮单层细胞中的ATP释放主要指向顶端培养基；然而，在基础条件和刺激条件下也观察到了ATP向基底外侧的释放。低渗以可逆方式增强了ATP向顶端和基底外侧培养基的释放。用特定渗透剂重建等渗条件或用机械敏感性离子通道阻滞剂抑制可减弱低渗诱导的ATP释放。通过发光测定法对从多个供体肾脏采集的ADPKD囊肿的“速冻”囊液进行了筛查。一部分囊液中含有高达0.5至10微摩尔的ATP，这些剂量足以刺激嘌呤能受体。综上所述，这些结果表明，ADPKD和非ADPKD人上皮细胞原代培养物在基础条件和刺激条件下均释放ATP，并且囊肿上皮细胞在体外和囊液中释放的ATP浓度足以刺激ATP受体。据推测，细胞外核苷酸的释放和信号传导可能对ADPKD的标志性特征——囊液体积的逐渐扩大产生有害影响。
