Parathyroid hormone (PTH) is regulated by such divalent cations as calcium ion (Ca⁺⁺) and magnesium ion (Mg⁺⁺), via adenylate cyclase (AC)-cyclic AMP system at least in part. Since the effects of various divalent cations on PTH secretion have never been compared in details, effects of various divalent cations on PTH secretion from and AC activity in bovine parathyroid cells in simultaneous experiments.
It was observed that Ca⁺⁺ has suppressive action on PTH secretion and AC activity, while Mg⁺⁺ and Mn⁺⁺ have biphasic suppressive effect. The set-point of Ca⁺⁺ for PTH secretion was 0.8mM and those for Mg⁺⁺ and Mn⁺⁺ were 1.0mM and 0.75mM, respectively. The set-points of Ca⁺⁺ Mg⁺⁺ and Mn⁺⁺ on AC activity were 0.8mM, 1.0mM and 1.0mM, respectively.
In view of the recent suggestion that the parathyroid disorder such as hyperparathyroidism represents an abnormality in the set-points of the parathyroid cells for metal ions, the measurement of set-points for divalent cations might provide a useful approach in study of the pathophysiology of parathyroid disorders.

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A case of parathyroid carcinoma associated with recurrent gastric ulcer was presented. The excretion of nephrogenous c-AMP, calcium, phosphate and magnesium, and serum levels of PTH, calcium, phosphate and magnesium were determined before and after parathyroidectomy.
Nephrogenous c-AMP and plasma N-PTH levels decreased rapidly to normal values within thirty minutes after removal of the tumor, though it took 15 hours for plasma levels of C- and M-PTH and serum calcium concentration to become normal. Excretion of urinary phosphate also decreased rapidly, indicating rapid disappearance of PTH action in the kindey. Therefore, nephrogenous c-AMP was shown to a good indication of biological activity of parathyroid hormone.
Gastric ulcer healed with no anti-ulcer medication after the surgery and the patient has been well without recurrence of the ulcer. There was neither hyperacidity of gastric juice nor hypergastrinemia before surgery. Hyperparathyroidism or hypercalcemia per se may have played the major role in the occurrence of gastric ulcer.

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Binding of parathyroid hormone (PTH) to rat osteosarcoma cells (ROS 17/2) was studied using ¹²⁵I labeled synthetic [Nle⁸, Nle¹⁸, Tyr³⁴] bovine (b) PTH-(1-34) amide as radioligand. Binding of ¹²⁵I-[Nle⁸, Nle¹⁸, Tyr³⁴] bPTH-(1--34) amide to ROS 17/2 cells is temperature-and timedependent, specific to bioactive PTH peptides, saturable, and reversible. Kd for the binding is 1.1×10^-9 M and numbers of apparently homogenous binding site for the radioligand are 2.8×10⁴ per cell. Receptors on cellular surface are regulated downward by PTH and 1, 25-(OH)₂-D₃ and upwards by hydrocortisone. These regulations are reversible and accompanied by changes in numbers of receptor having good correlations with PTH-stimulated adenylate cyclase in plasma membranes of ROS 17/2 cells. Thus, this study clearly demonstrates that regulation of PTH-receptor occurs by various substances and that further studies on the mechanism of receptor regulation are possible using ROS 17/2 cells.

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A review of patients experienced at this institution is reported with special reference to the diagnosis of primary hyperparathyroidism, idiopathic hypoparathyroidism and pseudohypoparathyroidism.
Primary hyperparathyroidism: Of the 39 cases experienced in the past six years, 33 (84.6%) could be diagnosed by a combination of hypercalcemia and elevated immunoreactive parathyroid hormone (iPTH). Patients with mild hypercalcemia and normal (4 patients) or slightly elevated iPTH levels were diagnosed by other ancillary laboratory findings, especially by the increase in nephrogenous cAMP. On the other hand, patients who have not distinctly elevated iPTH or periosteal bone resorption despite the profound hypercalcemia (more than 12-13mg/dl) are far more likely to have hypercalcemia of malignancy. Mean values of serum calcium concentrations were within normal range (<10.2mg/dl) in 2 patients (skeletal-and chemical hyperparathyroidism complicated with pancreatitis in the latter) and serum calcium concentrations of 10 patients were within the normal limits at least in one determination.
Hypoparathyroidism: At present, the differentiation of idiopathic hypoparathyroidism from pseudohypoparathyroidism depends on both serum iPTH assays and the Ellsworth-Howard test. Diagnostic criteria recently agreed in this country and several problems in the Ellsworth-Howard test are discussed.

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The contents of γ-carboxyglutamic acid (Gla) and calcium were studied as a function of bone maturation and mineralization during endochondral ossification induced by subcutaneous implantation of demineralized rat bone matrix, and the effects of warfarin were investigated in this model.
In normal rats, the Gla contents in the implants increased gradually and reached 8.3nmole on the 35th day; and the calcium content rose linearly. In warfarin treated rats, the increase of Gla content was inhibited, so that the content of Gla on the 35th day was only 2.2nmole, equal to that in normal rats on the 19th day. However, the calcium content of the implants in the warfarin treated rats increased more markedly than in normal rats.
In other words, calcium was accumulated to a greater extent in the very implants that inhibited the elevation of the Gla level. This suggests that Gla containing protein may play a regulating role in mineralization during bone formation.

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The effects of synthetic eel calcitonin analogue (ECT) on experimental renal osteodystrophy were investigated in rats. The nephritogenic glycopeptide (GP) was isolated by the method of Shibata et al.
The experimental renal failure was made by injecting GP into Wistar-Imamichi strain rats. 4 months after injection these rats excreted a lot of protein (200mg/day) and 10 months after injection they became chronic renal failure. ECT at the dose of 0.2u/kg, 1u/kg were administered to these rats for 2 months (from 8th month to 10th month) and for 6 months (from 4th month to 10th month).
The effect of ECT were evaluated by the data of blood chemistry, urinalysis, and bone histomorphometry.
In the group with renal failure (no ECT injection), rats had obvious renal osteodystrophy.
In the group, ECT 1u/kg were administered for 6 months, the values of urinary hydroxyproline were decreased compared with the group with renal failure (no ECT injection). Concerning the data of bone histomorphometry, resorption surface (FrRS) and mean osteoclast number (MCN) were decreased too. These data suggest that ECT might be effective in protecting renal osteodystrophy in these experimental rats.

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