[Modified cryopreservation of parathyroid gland tissue. Evaluation and comparison in an animal experiment].

A modified cryopreservation technique for parathyroid tissue was investigated in an animal model. The modified technique was compared with a previously described method [10, 11] using a programmed freezer and also with other simplified cryopreservation techniques [1, 8]. Total parathyroidectomy was performed in 90 Sprague-Dawley rats, which were allocated to 7 groups. Group I had no autotransplantation (n = 10) and group II underwent immediate autotransplantation of one parathyroid gland (n = 17). In the other five groups of rats the parathyroids were cryopreserved and one gland was reimplanted after 10 days' storage in liquid nitrogen (LN) at -196 degrees C. The following techniques for cryopreservation of the parathyroid glands were used. Group III: immediate placement in LN, n = 7; group IV: immediate placement in a freezer at -20 degrees C, transfer to LN after 2 h, n = 12; group V: immediate placement in a freezer at -80 degrees C, transfer to LN after 2 h, n = 13, group VI: manually controlled freezing initially at a rate of 1 degree C/min to -25 degrees C, and subsequently at 10 degrees C/min to -70 degrees C before transfer to LN [8], n = 19, group VII: programmed freezing at a controlled rate of 1 degree C/min to -80 degrees C prior to transfer to LN [10, 11], n = 12. Serum calcium concentrations were determined over a period of 60 days. Furthermore, the individual difference in the calcium concentration was assessed for each rat on the basis of the calcium levels recorded preoperatively and at day 60.(ABSTRACT TRUNCATED AT 250 WORDS)