The early phase of calcipenia-induced parathyroid hormone secretion is blunted in vasculary perfused parathyroid glands of streptozotocin-diabetic rats.

Objectives: To study effects of diabetes mellitus on parathyroid hormone (PTH) secretion, the rat parathyroid glands were perfused via the bilateral carotic arteries.
Material and Methods: Diabetic rats showed plasma glucose levels above 30 mmol/l, but no change in plasma PTH concentration, 14 days after an administration of 70 mg/kg of streptozotocin. Krebs-Ringer bicarbonate buffer containing 0.1% bovine serum albumin was used for perfusate. Perfusate calcium was lowered from 2.5 mmol/l to 0.5 mmol/l.
Results: In the normal rat parathyroid glands, PTH secretion was promptly evoked by calcipenia (from below 0.25 ng for 2.5 min in the perfusion with normal calcium to 0.73 +/- 0.17 ng during calcipenia time 0-2.5 min), and slightly decreased (0.51 +/- 0.12 ng during calcipenia time 2.5-5 min), and then increased (0.75 +/- 0.16 ng during calcipenia time 7.5-10 min). Diabetes abolished the early phase of PTH secretion (below 0.25 ng during calcipenia time 0-2.5 min), but did not affect the late phase of PTH secretion (0.64 +/- 0.14 ng during calcipenia time 7.5-10 min). Insulin treatment with 25 U/kg daily for 14 days completely normalized the early phase of PTH secretion.
Conclusion: It is suggested that an insulin-deficient diabetes, not quantitatively but qualitatively, impaires the PTH secretion.