Avoidance of direct injury to the peripheral nerve with maxacalcitol (22oxa-1,25(OH)2D3) in rats

Secondary hyperparathyroidism is one of the most common complications in patients with long-term end-stage renal disease. A recent report has stated that high doses of vitamin D derivatives injected directly into the parathyroid glands can reduce serum parathyroid hormone levels and suppress further enlargement of the parathyroid glands without side-effects. Maxacalcitol (22oxa-1,25(OH)(2)D(3); OCT) is a new vitamin D derivative that can be administered intravenously, and is available in Japan. Direct injection of OCT into enlarged parathyroid glands is a promising new treatment for moderate renal hyperparathyroidism. It is considered to be safe for surrounding tissues, such as peripheral nerves, but the actual effects of OCT on nerves have not yet been documented.

We measured nerve conduction velocity (NCV) in 24 rat femoral nerves soaked in saline, ethanol, or OCT at various concentrations. Nerves from each group (saline, ethanol, OCT groups) were also examined by microscopy.

The mean NCV of rat femoral nerves was 33.67 +/- 1.39 m/s in the saline group. In the OCT group, the velocities were not changed at any of the concentrations tested, and there were no significant differences in NCVs between the saline and OCT groups. In the 50% ethanol group, the velocity decreased significantly to 8.98 +/- 4.78 m/s (P < 0.01). A histological study demonstrated the nerves soaked in OCT at 10 microg/mL to essentially be intact, while those soaked in anhydrous ethanol were damaged.

This study demonstrated that OCT administration does not affect peripheral NCV, indicating that OCT could possibly be used for the treatment of moderate renal hyperparathyroidism safely without nerve damage.