Circadian variations in plasma calcium and calcitonin: effect of calcium deficiency and fasting

1985 ◽  
Vol 107 (3) ◽  
pp. 389-395 ◽  
Author(s):  
S. Lausson ◽  
J. F. Staub ◽  
G. Milhaud ◽  
A. M. Perault-Staub
Keyword(s):  
Calcium Concentration ◽  
Calcium Deficiency ◽  
Plasma Calcium ◽  
Simple Relationship ◽  
Feeding Period ◽  
Circadian Variations ◽  
Deficient Diet ◽  
Plasma Calcium Concentration ◽  
Old Rats ◽  
The Relationship

ABSTRACT Circadian fluctuations of plasma calcium and immunoassayable calcitonin levels were studied in normal and calcium-deficient 2-month-old rats. The relationship between these parameters was also studied in animals which had been fasted for short periods. The plasma calcium rhythm persisted and was even amplified in rats placed on a 4-week calcium-deficient diet. In these rats, as in normal rats, the plasma calcium concentration diminished during the dark period. Calcitonin levels increased at the onset of the feeding period in normal rats but, in calcium-deficient rats, the pattern changed completely, with a major peak at the end of the light period and remaining at a low level during the dark feeding period. This modification of calcitonin rhythmicity appeared to be dependent on the degree of calcium deficiency. Fasting had little effect on calcitonin rhythms in either normal or calcium-deficient rats. It is concluded that the calcitonin rhythm is relatively independent of feeding per se and that there appears to be no simple relationship between plasma calcium and calcitonin concentrations. It is suggested that the results may best be interpreted as reflecting the presence of rhythmic endogenous phenomena which are intrinsic to calcium metabolism and its regulation in the rat. J. Endocr. (1985) 107, 389–395

Nature of calcemic effect of 1,25-dihydroxyvitamin D3 in experimental hypoparathyroidism

1983 ◽  
Vol 244 (4) ◽  
pp. E313-E316
Author(s):  
E. Hefti ◽  
U. Trechsel ◽  
H. Fleisch ◽  
J. P. Bonjour
Keyword(s):  
Calcium Concentration ◽  
Calcium Absorption ◽  
Single Injection ◽  
Plasma Calcium ◽  
Constant Infusion ◽  
Feeding Period ◽  
Daily Fluctuation ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Plasma Calcium Concentration

The influence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] treatment on the daily fluctuation of plasma calcium concentration ( [Ca]P1) in relation to the feeding-fasting alternation has been studied in vitamin D-replete sham-operated (sham) and thyroparathyroidectomized (TPTX) rats fed a normal Ca diet. 1,25(OH)2D3 was given (26 or 39 pmol/day) intraperitoneally either by single injection or constant infusion using osmotic minipumps. After 7 days of treatment [Ca]P1 was measured at 4-h intervals for 24 h. Pair-fed, sham and TPTX animals received the solvent vehicle intraperitoneally. The results show that in sham rats the very moderate daily fluctuation of [Ca]P1 was not accentuated by 1,25(OH)2D3. A marked fluctuation of [Ca]P1 in relation to the food intake was observed in untreated TPTX as compared with sham rats. In TPTX rats 1,25(OH)2D3 increased the fasting [Ca]P1. In contrast the rise in [Ca]P1 during feeding was not significantly accentuated by 1,25(OH)2D3. The daily fluctuation of [Ca]P1 was the same whether the dose of 1,25(OH)2D3 was given in one single injection or by constant infusion, suggesting that this hormone is not involved in the hour-to-hour regulation of [Ca]P1. In conclusion, in the absence of parathyroid glands, 1,25(OH)2D3 given in doses that stimulate intestinal calcium absorption has a much more pronounced effect on the fasting calcemia than on the rise in calcemia observed during the feeding period. These results suggest that the mobilization of calcium from bone could play an important role in the calcemic effect of 1,25(OH)2D3 when given in the hypoparathyroid state.

ABOLITION OF MAGNESIUM-INDUCED HYPOCALCAEMIA BY ACUTE THYRO-PARATHYROIDECTOMY IN THE CAT

1970 ◽  
Vol 64 (1) ◽  
pp. 150-158 ◽  
Author(s):  
S. Pors Nielsen
Keyword(s):  
Sodium Chloride ◽  
Flow Rate ◽  
Magnesium Chloride ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Magnesium Concentration ◽  
Isotonic Sodium Chloride ◽  
Plasma Calcium Concentration ◽  
High Concentrations ◽  
Plasma Magnesium

ABSTRACT Intravenous infusion of isotonic magnesium chloride into young cats with a resultant mean plasma magnesium concentration of 7.7 meq./100 g protein was followed by a significant lowering of the plasma calcium concentration in 90 minutes. The rate of decrease of plasma calcium is consistent with the hypothesis that calcitonin is released by magnesium in high concentrations. There was no decrease in the plasma calcium concentration in cats of the same weight thyroparathyroidectomized 60 min before an identical magnesium chloride infusion or an infusion of isotonic sodium chloride at the same flow rate. The hypercalciuric effect of magnesium could not account for the hypocalcaemic effect of magnesium. Plasma magnesium concentration during magnesium infusion into cats with an intact thyroid-parathyroid gland complex was slightly, but not significantly higher than in acutely thyroparathyroidectomized cats.

Effect of Small Increments in Plasma Calcium Concentration on the Responsiveness of Forearm Resistance Vessels to Verapamil in Normal Subjects

1984 ◽  
Vol 67 (6) ◽  
pp. 613-618 ◽  
Author(s):  
B. F. Robinson ◽  
R. J. W. Phillips
Keyword(s):  
Calcium Concentration ◽  
Venous Blood ◽  
Normal Subjects ◽  
Plasma Calcium ◽  
Calcium Handling ◽  
Membrane Function ◽  
Resistance Vessels ◽  
Initial Control ◽  
Plasma Calcium Concentration ◽  
Small Increments

1. The effect of a small increase in local plasma calcium concentration on the responsiveness of the forearm resistance vessels to verapamil has been examined in normal subjects, by using a plethysmographic method with infusion of calcium and other agents into the brachial artery. 2. Infusion of calcium at a rate which increased the concentration in forearm venous blood by about 0.5 mmol/l caused basal blood flow to fall by 19% and the dilator response to verapamil to fall by 35% (n = 8; P<0.02). 3. When, after 46 min, the infusion of calcium was discontinued, the dilator response to verapamil increased to reach a level 53% higher than the initial control (n = 8; P<0.02). 4. Infusion of calcium had no effect on the dilator response to sodium nitroprusside. 5. Infusion of noradrenaline at a rate which caused a greater reduction in basal flow than that induced by calcium had no effect on the response to verapamil. 6. It is concluded that the dilator response to verapamil, which is thought to reflect activity of the potential operated system for calcium entry, is selectively depressed by a small elevation of plasma calcium concentration, but subsequently becomes elevated. These findings point to an important role for calcium in the regulation of membrane function in the resistance vessels and support the view that altered calcium handling may contribute to the development of primary hypertension.

CALCIUM AND THE CONTROL OF CIRCADIAN MITOTIC ACTIVITY IN RAT BONE MARROW AND THYMUS

1974 ◽  
Vol 62 (3) ◽  
pp. 451-462 ◽  
Author(s):  
N. H. HUNT ◽  
A. D. PERRIS
Keyword(s):  
Bone Marrow ◽  
Mitotic Activity ◽  
Calcium Homeostasis ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Ionized Calcium ◽  
Plasma Phosphate ◽  
Circadian Changes ◽  
Plasma Calcium Concentration ◽  
Rat Bone

SUMMARY Circadian changes in mitotic activity in rat bone marrow and thymus have been demonstrated to closely parallel variations in total and ionized calcium concentrations in plasma. These fluctuations in plasma calcium concentration and tissue mitosis were abolished by parathyroidectomy. Significant changes in plasma phosphate and magnesium concentrations were also observed over the 24 h period. The evidence suggests that hour-to-hour variations in the systems controlling calcium homeostasis determine the levels of mitosis in rat bone marrow and thymus.

Effect of calcitonin on calcium and magnesium transport in rat nephron

1980 ◽  
Vol 238 (6) ◽  
pp. E573-E578 ◽  
Author(s):  
G. A. Quamme
Keyword(s):  
Calcium Concentration ◽  
Transport Model ◽  
Distal Tubule ◽  
Urinary Calcium ◽  
Plasma Calcium ◽  
Loop Of Henle ◽  
Plasma Calcium Concentration ◽  
Calcium And Magnesium ◽  
Magnesium Excretion

Renal calcium and magnesium reabsorption was investigated in young, thyroparathyroidectomized rats receiving synthetic salmon calcitonin. Kidney and tubular function was assessed by clearance and in vivo microperfusion techniques, respectively. Calcitonin reduced urinary calcium and magnesium excretion that was attributed to increased reabsorption within the loop of Henle. This enchanced reabsorption was independent of parathyroid hormone; however, it is contingent on a decline in plasma calcium concentration. Prevention of hypocalcemia by CaCl2 infusion in rats acutely administered calcitonin resulted in loop function comparable to animals not receiving the hormone. Calcitonin had little effect on proximal tubule or distal tubule electrolyte reabsorption. These results are consistent with a transport model for calcium and magnesium in the loop of Henle involving a contraluminal transfer step modulated by absolute extracellular calcium or magnesium. Furthermore, these studies suggest that the discrepancies present in the literature concerning renal effects of calcitonin on electrolyte reabsorption are due to variations in observed hormone action, namely, the effect on plasma calcium concentration.

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