Parathyroid hormone stimulation of the renal 25-hydroxyvitamin D-1α-hydroxylase—Effect of age and free radicals

Certain parathyroid hormone (PTH) analogues have been shown to selectively impair some but not all physiological actions of PTH. In this study, transaminated rat (r) PTH [TA-rPTH-(1-34)], a PTH analogue that differs from the rPTH-(1-34) fragment in that the NH2-terminal alanine is converted to pyruvate, was infused into mice to determine its properties in vivo and specifically to determine whether stimulation of 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase) activity was more dependent on concomitant renal handling of phosphate or on generation of adenosine 3',5'-cyclic monophosphate (cAMP). High-performance liquid chromatography-purified TA-rPTH-(1-34) was infused into C57BL mice at 10 or 30 pmol/h for 24 h. At 30 pmol/h, TA-rPTH-(1-34) was comparable with rPTH-(1-34) in its hypophosphatemic and phosphaturic effects but was less potent than rPTH-(1-34) in raising serum calcium. TA-rPTH-(1-34) was markedly less effective in stimulating renal 1 alpha-hydroxylase than rPTH-(1-34). Stimulation of urinary cAMP excretion occurred after infusion with TA-rPTH-(1-34), but this effect was significantly less than that seen with rPTH-(1-34). These findings indicate that PTH-induced hypophosphatemia and phosphaturia can be uncoupled from PTH stimulation of 1 alpha-hydroxylase. Furthermore, cAMP-related signal transduction appears to be more significant in regulation of 1 alpha-hydroxylase than mechanisms that mediate PTH-sensitive phosphate transport, independent of cAMP.

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Parathyroid hormone-independent regulation of 1,25(OH)2D in response to inhibition of bone resorption

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1988.254.3.e260 ◽

1988 ◽

Vol 254 (3) ◽

pp. E260-E264

Author(s):

J. P. Bonjour ◽

U. Trechsel ◽

C. M. Taylor ◽

H. Fleisch

Keyword(s):

Parathyroid Hormone ◽

Bone Resorption ◽

Marked Rise ◽

Absorption Increase ◽

Hydroxyvitamin D ◽

Dihydroxyvitamin D ◽

25 Hydroxyvitamin D ◽

Intestinal Ca Absorption ◽

Homeostatic Response ◽

Stimulation Of

Both plasma level of 1,25-dihydroxyvitamin D [1,25(OH)2D] and intestinal Ca absorption increase after biphosphonate-induced inhibition of bone resorption. Parathyroid hormone (PTH) has been considered a key mediating element of this homeostatic response. In the present work, the role of PTH was assessed by studying the influence of 1-hydroxypentane-1,1-bisphosphonate (HPeBP) on vitamin D and Ca metabolism in both intact and thyroparathyroidectomized (TPTX) rats. In intact rats, HPeBP given at 0.1 mg P/kg body wt sc for 10 days strongly inhibited bone resorption without affecting bone formation. This effect was associated with a marked stimulation of intestinal Ca absorption and Ca balance. In this condition, HPeBP caused a marked rise in plasma 1.25(OH)2D without affecting the level of 25-hydroxyvitamin D. In TPTX rats, HPeBP given at same dose also inhibited bone resorption and enhanced plasma 1,25(OH)2D, intestinal Ca absorption and Ca balance. In summary, this study shows that bisphosphonates such as HPeBP with prevailing inhibitory activity on bone resorption induce a marked stimulation of both 1,25(OH)2D production and intestinal Ca absorption. This homeostatic response is not attenuated after PTH removal. Thus, as previously shown for the response to low Ca diet, PTH does not appear to be an essential mediating factor for stimulating 1,25(OH)2D production in response to an increase in bone mineral retention.

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Level of calcium intake modifies the correlation between parathyroid hormone and 25-hydroxyvitamin D: a proposal of adequate 25-hydroxyvitamin D levels in children

Bone Abstracts ◽

10.1530/boneabs.2.oc13 ◽

2013 ◽

Author(s):

Loreto Reyes Maria ◽

Molina Marcela ◽

Escobar Raul ◽

Isabel Hernandez Maria ◽

Cavada Gabriel ◽

...

Keyword(s):

Parathyroid Hormone ◽

Calcium Intake ◽

Hydroxyvitamin D ◽

25 Hydroxyvitamin D

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Vitamin D Deficiency and Seasonal and Inter-day Variation in Circulating 25-hydroxyvitamin D and Parathyroid Hormone Levels in Indoor Daytime Workers: A Longitudinal Study

Industrial Health ◽

10.2486/indhealth.ms1255 ◽

2011 ◽

Vol 49 (4) ◽

pp. 475-481 ◽

Cited By ~ 15

Author(s):

Hiroaki ITOH ◽

Ippei MORI ◽

Yuki MATSUMOTO ◽

Syou MAKI ◽

Yasutaka OGAWA

Keyword(s):

Vitamin D ◽

Parathyroid Hormone ◽

Longitudinal Study ◽

Vitamin D Deficiency ◽

Hormone Levels ◽

Hydroxyvitamin D ◽

25 Hydroxyvitamin D

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Prevalence of vitamin D level in the serum of patients living in Erbil city, Iraq, referred to private clinical laboratory and effect of age and sex on it

Journal of Biological Research - Bollettino della Società Italiana di Biologia Sperimentale ◽

10.4081/jbr.2018.6916 ◽

2018 ◽

Vol 91 (1) ◽

Author(s):

Rabar M. Abdulrahman ◽

Balen Muhsin Abdul Rahman

Keyword(s):

Vitamin D ◽

Clinical Laboratory ◽

Mediterranean Country ◽

Hydroxyvitamin D ◽

Vitamin D Levels ◽

Study Population ◽

25 Hydroxyvitamin D ◽

Country People ◽

Effect Of Age ◽

Age And Sex

This retrospective study aimed to determine the levels of 25- hydroxyvitamin D [25-(OH) D] in the individuals that have been referred to two laboratories (Bio Lab and King Lab) and to around 50 private side laboratories that use both Bio Lab and King Lab as a referral lab for their tests, in Erbil city, Iraq. Then show the range of deficiency and its relation with sunlight exposure, sex and age. Out of the total number of cases (N=10823), large percentage (nearly 78%) referred to both clinical laboratory based in Erbil city were found to have a deficiency in vitamin D levels, which means they had 25-(OH) D levels lower than 20 μg/L. This study found the percentage of vitamin D level in the serum of groups insufficient, deficient, adequate, optimal; intoxication were 52.8, 24.1, 11, 12 and 0.2% respectively. When the records have been compared according to gender, the results suggested that there was no difference between male and female within the study population (P>0.05), while there was difference in the grouped ages (P<0.05). Our results indicate that although Erbil is located in a Mediterranean country, people living there should periodically check their 25-(OH) D levels, in order to get appropriate supplements of vitamin D, which eventually prevents secondary chronic disease due to vitamin D deficiency.

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