Objective      To investigate the feasibility of the application of 5-aminolevulinic acid (5-ALA)-induced fluorescence for the detection of parathyroid glands in secondary hyperparathyroidism rats and to observe the dynamic changes of the accumulation of endogenous synthesized protoporphyrin Ⅸ (PpⅨ) after administration of 5-ALA.       Methods      Twelve female Sprague-Dawley rats

weighing 180-200 g

were divided into 2 groups: an operation grou

p (5/6 nephrectomy plus high phosphorus food) and a sham operation group (normal phosphorus food). After 28 d

the two groups of rats were photosensitized by intraperitoneal injection of ALA solution. After surgical exposure of thyroid gland and parathyroid gland

the operative sites were observed under blue light (405nm) using a miniature fiber optic spectrometer to assess the fluorescence intensity of thyroid and parathyroid tissues. Histological examination of the fluorescent tissues was performed.       Results      After intraperitoneal injection of 5-ALA

parathyroid gland fluorescence was observed in two groups of rats. The red fluorescence of parathyroid glands was located on the posterolateral thyroid glands and could be seen by naked eyes. The red fluorescence of the parathyroid glands could be seen from 0.5 h to 4 h in the operation group and from 1 h to 3 h in the sham operation group. The peak intensity at 2 h in the operation group was significantly higher than that in the sham operation group (

P

0.05)

and the fluorescence intensity was 10 times higher in the parathyroid glands than in the thyroid gland in both of the two groups. The histology of the fluorescent tissues confirmed the tissue with red fluorescence was the proliferated parathyroid gland under a light microscope.       Conclusion      5-ALA-induced high intensity fluorescence suggests an important support to identify the hyperplastic parathyroid glands rather than normal glands and improve the success of parathyroidectomy. It has potential clinical value in treatment of parathyroid diseases.