Paraphysectomy-induced stimulation of parathyroid glands in mature frogs ( Rana catesbeiana) : Evidence for telencephalic regulation of parathyroid gland function

The relationship of the paraphyseal-choroid plexus complex to parathyroid gland function was investigated in adult frogs. Light microscopy and morphometric analysis indicated that total parathyroid gland volume, cell volume and vascular volume doubled by 7–28 days after surgical removal of the paraphyseal-choroid plexus complex (paraphysectomy). This increase correlated with the appearance of (1) large Golgi-associated vesicles, (2) an increase in the apparent number of cytoplasmic dense-core granules, and (3) PTH within the parenchymal cells as monitored by imrnunofluorescence. Twelve months after paraphysectomy, parathyroid glands became cystic with a central fluid-filled cavity surrounded by a stratified cuboidal cell layer. The parenchymal cells of cystic glands contained numerous cytoplasmic dense-core granules and were also positive for PTH. Radioimmunoassay of cystic parathyroid fluid indicated a PTH concentration of 2 μg/μ1; however, analysis by SDS-PAGE indicated a wide range of proteins in cystic fluid. The results of this study indicate that paraphysectomy induces stimulation of the parathyroid glands and suggest a role for the paraphyseal-choroid plexus complex in the regulation of amphibian parathyroid gland function.