Although the genetic basis of autosomal dominant polycystic kidney disease (ADPKD) is known, the mechanism(s) of cyst formation and growth remains unclear. One possible mechanism is the activation of ATP-sensitive P2 receptors in the cells lining the cysts. Stimulation of a putative P2 receptor by ATP, acting in an autocrine or paracrine fashion, may stimulate Cl^– and fluid secretion and thus contribute to cyst expansion, as well as affect cell turnover, which can also affect cyst growth. In this study we investigated the effect of P2 receptor inhibition on cyst growth in a Madin Darby canine kidney (MDCK) cell culture model of renal cyst formation.

MDCK cells were cultured in collagen gels in the presence of the cAMP agonist forskolin to stimulate cyst formation, using a modification of the method of Grantham et al. (1989). Briefly, cells were suspended in vitrogen (~3.0 mg ml^-1 collagen; Cohesion Technologies Inc., Palto Alto, USA), seeded onto 24-well plates and after gelation occurred, overlaid with growth media containing 10 µM forskolin. We tested the effects of three non-selective P2 receptor inhibitors: 100 µM suramin, 100 µM Pyridoxal-phosphate-6-azophenyl-2Ô,4Ô-disulfonate (PPADS), and 100 µM Reactive blue 2 (RB2). For each treatment, n = 40-54 cysts. The diameter of each cyst was measured directly from photographs using images that had been magnified to the same extent.

Suramin and RB2 significantly reduced the increase in cyst volume by 39.45 % (P = 0.001; Student’s paired t test) and 60.20 % (P = < 0.001), respectively. PPADS reduced the increase in cyst volume by 13.83 %, but this was not significant.

These findings support the hypothesis for a role of P2 receptors in renal cyst growth and enlargement. However, these initial observations require more study, since there are many P2 receptor subtypes, one or other of which might prove to be a therapeutic target to limit cyst growth and preserve renal function.

This work was supported by the St Peter’s Trust (Les Clark Fund). We thank Dr D. Sheppard and Dr H. Li for help in establishing the MDCK cyst model, and Dr B. King for helpful discussions.