BACKGROUND/AIMS:Renal osteodystrophy and eventually osteoporosis are serious long-term complications in children with end-stage renal disease before and after renal transplantation. Strontium (Sr) salts are used for treatment of osteoporosis in adults.METHODS:To evaluate the time-dependent effects of Sr on growth plate morphology and their reversibility, chronic renal failure (CRF) rats received either normal or Sr-loaded drinking water (2 g/l; ±200 mg/kg/day) for periods of 2, 6 and 12 weeks with or without subsequent washout periods of 0, 2, 4 or 8 weeks.RESULTS:While weight gain was not affected by Sr loading, a significant enlargement of the entire growth plate, mainly due to expansion of the hypertrophic zone, was already present after 2 weeks. Sr-loaded animals showed increased osteoid areas and reduced bone formation rates at 2, 6 and 12 weeks compared to controls. This was accompanied by reduced PTH levels and increased serum bone alkaline phosphatase activity. After the washout periods these effects were reversed. In general, the height of the hypertrophic zone was positively correlated with osteoid area and negatively correlated with bone formation rate.CONCLUSION:Moderate Sr loading in CRF rats results in rapid development of rickets, which is reversible after washout.

Nephrology has a long tradition in the Czech Republic. The first acute dialysis was performed in 1955, a chronic dialysis programme started in the early 60ies, and a transplantation programme in 1966. This was reflected by many important international meetings held in Prague: The 2nd Congress of the International Society of Nephrology (1963), 17th Congress of the European Dialysis and Transplantation Association (1980) and the 15th Congress of the European Society of Artificial Organs (1988). More recently, the 17th and 25th meetings of the International Society of Blood Purification (1999 and 2007), 11th ANCA and Vasculitis Workshop (2003), 7th European Peritoneal Dialysis Meeting (2005), 13th Congress of the European Society of Organ Transplantation (2007) and finally, this year, the 48th Congress of ERA-EDTA.

Bisphosphonates have been shown to attenuate ectopic calcification in experimental uremia. While they are known to reduce bone turnover, the effects on endochondral bone formation have not yet been addressed. To address this issue, we administered male Sprague-Dawley rats weekly subcutaneous injections of either vehicle or ibandronate (1.25 μg/kg body weight) for a total of 10 weeks. The rats were randomly allocated into one of four groups: (1) vehicle-treated, sham-operated rats; (2) ibandronate-treated, sham-operated rats; (3) vehicle-treated, 5/6 nephrectomized rats; (4) ibandronate-treated, 5/6 nephrectomized rats. Bones were double labeled with tetracycline and demeclocycline in vivo, and tibiae were removed for analysis. Weight gain was similar in all groups. Ibandronate reduced body length gain and tibial growth rate in the sham-operated animals but not in the rats showing chronic renal failure (CRF). The height of the proliferative zone of the epiphyseal growth plate was reduced in the ibandronate-treated controls and tended to be reduced in CRF rats. A significant correlation between tibial growth rate and height of the proliferative zone was observed. Mineral apposition rates were significantly reduced in ibandronate-treated, sham-operated rats and tended to be reduced in CRF rats. In conclusion, ibandronate interferes with tibial growth and bone mineralization in young rats with normal and reduced renal function.