Parathyroid hormone release from the perfused canine thyroid-parathyroid complex isolated in situ

A model for direct measurement of hormone release from the canine parathyroid gland is described. The two separate thyroid-parathyroid gland complexes were isolated in situ and perfused independently using a synthetic medium with a welldefined concentration of ionized calcium (Ca++). The concentration of parathyroid hormone (PTH) in the effluent was measured by radioimmunoassay, using an antiserum to bovine PTH that cross-reacts with canine PTH. Displacement curves of dilutions of effluent samples were similar to those of bovine PTH (1-84). During infusion of 1.49 mmol/l Ca++ the PTH release was constant for more than 4 h. Variations in Ca++ from 1.56 to 1.15 or 2.15 mmol/l induced rapid and sustained stimulation or suppression of PTH release. The retained ability of the preparation was ascertained by recording the response to infusion of calcium free medium at the end of each experiment.