Calcitonin-induced alterations to the ultimobranchial and parathyroid glands in the garden lizard Calotes versicolor


Abstract: Calotes versicolor specimens were divided into 2 groups of equal quantity (groups A and B). Group A was injected daily with 0.1 mL/50 g bw of vehicle. Group B was injected daily with 0.5 \mug/50 g bw of salmon calcitonin. Lizards in each group were sacrificed 2 h after the last injection on the 1st, 3rd, 5th, 10th, and 15th day of treatment. After collection of blood samples, ultimobranchial and parathyroid glands were fixed. The plasma calcium level in the lizards treated with calcitonin decreased on day 1. This response progressed up to day 5; thereafter the level was elevated, so that on day 15 a normal plasma calcium level was achieved. No change in plasma phosphate levels from day 1 was observed following calcitonin treatment. Progressive hypophosphatemia was observed from day 3 to 5; thereafter the level tended to rise and resulted in normophosphatemia on day 15. The ultimobranchial gland in the lizards treated with calcitonin did not exhibit any histological alterations up to day 5. The nuclear volume of ultimobranchial cells decreased on day 10 and persisted until day 15. Additionally, few degenerating cells were observed after 15 days of calcitonin treatment. The parathyroid gland in C. versicolor was unaffected up to day 3 following calcitonin treatment. A progressive increase in the nuclear volume of parathyroid cells was observed from day 5 until the end of the experiment (day 15); the gland became compact on days 10 and 15. In addition, few degenerating cells were observed after 15 days of calcitonin treatment.

Keywords: Calcitonin, ultimobranchial gland, parathyroid gland, lizard, plasma calcium, plasma phosphate, Calotes versicolor

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