[Intestinal absorption of Ca47 in chronic renal insufficiency before and after treatment with 1,25 dihydroxycholecalciferol]

The effects of vitamin D3 follow its metabolisation in the liver and then in the kidney. Its most active metabolite is 1,25 (OH)2D3, produced by the liver precursor 25(OH)D3. In chronic renal insufficiency, demineralising osteopathy can be corrected by administering 1,25 (OH)2D3 to make up for its under-production by the kidneys. An assessment if is made of 47Ca intestinal transport in patients with chronic renal insufficiency before and after such treatment. It was found that the effects of the metabolite on calcium transport were dose-dependent.

Effects of 1,25-dihydroxycholecalciferol on 47calcium absorption in post-menopausal osteoporosis

Measurement of 47Calcium absorption was performed on eleven women with post-menopausal osteoporosis. The study was repeated after 10 days treatment with 1 microgram daily of 1,25(OH)2D3. These patients showed a statistically significant improvement of fractional calcium absorption that was inversely correlated to the basal values. The prompt improvement of the intestinal calcium transport in post-menopausal osteoporotic women, a few days after the administration of physiological doses of 1,25(OH)2D3, suggests that these patients synthesize inappropriately small amounts of 1,25(OH)2D3 because of their oestrogen deficiency. This could be an important pathogenetic factor in post-menopausal osteoporosis, as the efficiency of the adaptation of calcium absorption to low calcium intakes is dependent on 1,25(OH)2D3.

Prostaglandin PGE2: a possible mechanism for bone destruction in calcinosis circumscripta

A patient showed evident osteolysis in phalanges and heavy periarticular calcium deposits of the fingers, wrists and toes which avidly took up 47Ca. The dense, white, tooth-paste like fluid contained in the periarticular calcium deposits has been studied by two different X-ray diffraction methods, by Ubatuba's bioassay for prostaglandin, by thin layer chromatography and by mass spectrometry. The calcium deposits were hydroxyapatite and prostaglandin PGE2 was detected in them. The bone resorption stimulating activity of PGE2 would be expected to result in increased bone destruction with release of calcium salts and this could be a working hypothesis of the pathogenesis of calcinosis circumscripta.

Effects of a new glucocorticoid, oxazacort, on some variables connected with bone metabolism in man: a comparison with prednisone

The urinary elimination of calcium, other electrolytes, and hydroxyproline and the oral absorption of 47Ca have been evaluated in three groups of 8 patients before and during a 15-day treatment with prednisone at daily doses of 25 and 50 mg and with oxazacort, a new glucocorticoid, at a daily dose of 50 mg. The results obtained demonstrate that oxazacort in short-term teatment with a high dose has no significant effect on the urinary elimination of calcium and hydroxypyroline in experimental conditions in which prednisone produces statistically significant and clinically relevant increase, both when given at the same dose and when given at half that dose. On the other hand, the oral absorption of 47Ca is decreased by oxazacort, but less than by prednisone at the same dose. As the antirheumatic activity of oxazacort appears to be only slightly lower than that of prednisone (activity ratio of about 0.84: 1), these findings may have interesting therapeutic implications.

Indirect evidence of calcitonin secretion in man

1. The effect of calcitonin, a large amount of calcium given orally, pentagastrin and glucagon on plasma 47Ca radioactivity curves in subjects pretreated with 47Ca was examined. 2. A sudden increase of plasma radioactivity after intravenous administration of calcitonin and pentagastrin and after the oral calcium load was observed in normal subjects; the intravenous infusion of glucagon was less effective. 3. Two thyroparathyroidectomized patients who responded to the calcitonin infusion did not respond to the oral calcium load. 4. These data may be considered to offer indirect evidence of endogenous calcitonin secretion in man.

Early effects of synthetic bovine parathyroid hormone and synthetic salmon calcitonin on urinary excretion of cyclic AMP, phosphate and calcium in man

Bovine synthetic parathyroid hormone infused intravenously in man increased both the urinary excretion of cyclic AMP and the urinary excretion of phosphate whereas a Salmon synthetic calcitonin infusion increased the urinary excretion of phosphate without change in urinary excretion of cyclic AMP. These data are consistent with the hypothesis that different renal mechanisms are involved in the response to each hormone.

[Treatment of Paget's disease with diphosphonate (disodium ethydronate)]

16 patients suffering from Paget's disease were studied before, during and after 3 or 6 month treatment with disodium ethydronate (EHDP) per os. An appreciable improvement in pain symptomatology was noted and at times an evident improvement in audiometry; from the metabolic viewpoint there was a fall in serum alkaline phosphatase and urinary excretion of calcium and hydroxyproline. A study of radiocalcium kinetics demonstrated a reduction in the exchangeable calcium pool and the fractional turnover rate. Histological examination following needle biopsy of the iliac crest showed evident diminution in the active bone cell population (osteoclasts, osteoblasts) and, in certain cases, appearance of osteoid borders.

Initial increase of plasma radioactive calcium after intravenous injection of calcitonin in man

1. An intravenous infusion of calcitonin produced a sudden increase of plasma radioactivity after intravenous administration of 47Ca in man.

2. This effect was noted a few minutes before the well-known decrease of plasma calcium concentration.

3. A mathematical evaluation of this phenomenon demonstrated that: (a) it was significant in normal subjects, provided patients were given calcitonin 60–360 min after the intravenous injection of 47Ca; (b) it was generally not significant in patients with senile osteoporosis or osteomalacia; (c) it was particularly evident in patients with generalized Paget's disease or multiple myeloma.

4. Surface measurements performed on soft tissues and bone demonstrated a transient, simultaneous decrease of 47Ca radioactivity from bone.

5. The increase in plasma radioactivity implies a shift of 47Ca from reservoirs with high specific radioactivity, possibly bone cells, to the circulation.

6. According to these data two different mechanisms of action of calcitonin could be considered: an early effect on bone cells producing a shift of calcium to the circulation, and the well-known later hypocalcaemic effect through diminution of bone resorption.