Hyperphosphataemia sensitizes renally impaired rats to the profibrotic effects of gadodiamide.

background and purposeHyperphosphataemia is common in patients with nephrogenic systemic fibrosis (NSF). NSF has been linked to administration of gadolinium (Gd) chelates (GCs) and elevated serum phosphate levels accelerate the release of Gd from linear, non-ionic GCs but not macrocyclic GCs. Hence, we determined whether hyperphosphataemia is a cofactor or risk factor for NSF by investigating the role of hyperphosphataemia in renally impaired rats. EXPERIMENTAL APPROACH: Firstly, the clinical, pathological and bioanalytical consequences of hyperphosphataemia were investigated in subtotal nephrectomized (SNx) Wistar rats following i.v. administration of the non-ionic, linear GC gadodiamide (5 × 2.5 mmol·kg(-1) ·day(-1) ). Secondly, the effects of several GCs were compared in these high-phosphate diet fed rats. Total Gd concentration in skin, femur and plasma was measured by inductively coupled plasma mass spectrometry (ICP-MS) and free Gd(3+) in plasma by liquid chromatography coupled to ICP-MS. Relaxometry was used to measure dissociated Gd in skin and bone. KEY

resultsFour out of seven SNx rats fed a high-phosphate diet administered gadodiamide developed macroscopic and microscopic (fibrotic and inflammatory) skin lesions, whereas no skin lesions were observed in SNx rats treated with saline, the other GCs and free ligands or in the normal diet, gadodiamide-treated group. Unlike the other molecules, gadodiamide gradually increased the r(1) relaxivity value, consistent with its in vivo dissociation and release of soluble Gd. CONCLUSIONS AND IMPLICATIONS: Hyperphosphataemia sensitizes renally impaired rats to the profibrotic effects of gadodiamide. Unlike the other GCs investigated, gadodiamide gradually dissociates in vivo. Our data confirm that hyperphosphataemia is a risk factor for NSF.