25-Hydroxycholecalciferol 1α-Hydroxylase Activity in the Kidney of the Fetal, Neonatal and Adult Guinea Pig

Neonatology ◽  
1980 ◽  
Vol 37 (5-6) ◽  
pp. 254-256 ◽  
Author(s):  
Enid Fenton ◽  
H.G. Britton
Keyword(s):  
Guinea Pig ◽  
Hydroxylase Activity ◽  
25 Hydroxycholecalciferol

Submitochondrial localization of kidney 25-hydroxycholecalciferol 1α-hydroxylase in vitamin D repleted weanling guinea pigs

1987 ◽  
Vol 65 (7) ◽  
pp. 673-676 ◽  
Author(s):  
Xue Yan ◽  
Guy Charette ◽  
Edgard E. Delvin
Keyword(s):  
Vitamin D ◽  
Cytochrome C ◽  
Guinea Pig ◽  
Guinea Pigs ◽  
Membrane Fraction ◽  
Hydroxylase Activity ◽  
Oxidoreductase Activity ◽  
Pig Kidney ◽  
Steroid Hydroxylases ◽  
25 Hydroxycholecalciferol

We have studied the submitochondrial localization of guinea-pig kidney 25-hydroxycholecalciferol 1α-hydroxylase. Treatment of the mitochondrial-enriched fraction with recrystallized digitonin produced mitoplasts bordered by a single membrane and with intact matrix. They contained nearly 90% of the 25-hydroxycholecalciferol 1α-hydroxylase activity and nearly 100% of the cytochrome-c: oxygen oxidoreductase. Amine: oxygen oxidoreductase activity remained mainly in the outer membrane fraction. These data show that 25-hydroxycholecalciferol 1α-hydroxylase has a distribution similar to that of steroid hydroxylases.

Development of phenylalanine hydroxylase activity in guinea pig liver

1972 ◽  
Vol 261 (2) ◽  
pp. 315-320 ◽  
Author(s):  
Helen K. Berry ◽  
Roberta Cripps ◽  
Kay Nicholls ◽  
David McCandless ◽  
Calvin Harper
Keyword(s):  
Guinea Pig ◽  
Phenylalanine Hydroxylase ◽  
Hydroxylase Activity ◽  
Pig Liver ◽  
Guinea Pig Liver

scholarly journals Dietary calcium and phosphate restriction in guinea-pigs during pregnancy: fetal mineralization induces maternal hypocalcaemia despite increased 1α,25-dihydroxycholecalciferol concentrations

2000 ◽  
Vol 84 (4) ◽  
pp. 495-504 ◽  
Author(s):  
Katrien Rummens ◽  
Erik Van Herck ◽  
Rita van Bree ◽  
Roger Bouillon ◽  
F. André Van Assche ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Plasma Concentrations ◽  
Dual Energy ◽  
Whole Body ◽  
Hydroxylase Activity ◽  
Mineral Density ◽  
X Ray ◽  
Highly Correlated ◽  
Stimulation Of

Guinea-pig fetuses at term are mineralized to a degree comparable with human fetuses, which makes the guinea-pig an attractive animal model to study maternal–fetal interactions with regard to Ca and phosphate (P) homeostasis. We studied non-pregnant and pregnant (day 57) vitamin D-replete guinea-pigs, fed either a normal guinea-pig chow with 9·6 g Ca/kg and 4·9 g P/kg or a study diet with 2 g Ca/kg and 1 g P/kg (low-Ca–P diet) for 7–8 weeks. Both pregnancy and the low-Ca–P diet decreased plasma concentrations of 25-hydroxycholecalciferol (25(OH)D3), but increased total and free 1α,25-dihydroxycholecalciferol (1,25(OH)2D3), strongly suggesting an additive stimulation of 1α-hydroxylase activity. Maternal and fetal 25(OH)D3and 1,25(OH)2D3levels were highly correlated (r0·82 and 0·92 respectively, P<0·001). Dual-energy absorption X-ray absorptiometry (DXA) showed that both pregnancy and the low-Ca–P diet decreased bone mineral density (BMD) of the maternal femur, particularly at the distal metaphysis. Despite higher 1,25(OH)2D3concentrations and lower BMD, pregnant animals on the low-Ca–P diet were hypocalcaemic; blood Ca2+levels were inversely correlated with the number of fetuses in this group (r-0·93, P<0·001). Fetal growth as well as mineralization (assessed by whole-body and femoral DXA, bone histomorphometry and plasma–bone osteocalcin measurements) were unaltered in the low-Ca–P group. In conclusion, fetal mineralization proceeds normally but induces maternal hypocalcaemia in guinea-pigs with dietary restriction of Ca and P.

Effects of C19 steroids on adrenal steroidogenic enzyme activities and their mRNA levels in guinea-pig fasciculata-glomerulosa cells in primary culture

1992 ◽  
Vol 132 (2) ◽  
pp. 269-276 ◽  
Author(s):  
P. H. Provencher ◽  
Y. Tremblay ◽  
A. Bélanger
Keyword(s):  
Guinea Pig ◽  
Primary Culture ◽  
Oxygen Tension ◽  
Enzyme Activities ◽  
Inhibitory Effect ◽  
Mrna Levels ◽  
Hydroxylase Activity ◽  
Steroidogenic Enzymes ◽  
Steroidogenic Enzyme ◽  
Steroid Synthesis

ABSTRACT The present study examined the effects of steroids on steroidogenic enzyme activity in adrenal glands. Guinea-pig fasciculata-glomerulosa (FG) cells maintained in primary culture were exposed to steroids for 48 h. Although the treatment with androstenedione alone had no effect on 3β-hydroxysteroid dehydrogenase 4-ene-5-ene-isomerase (3β-HSD), 17-hydroxylase and 17,20-lyase activities, there was inhibition of 11-hydroxylase and 21-hydroxylase activities. When FG cells were exposed to 10 nmol ACTH/l for the last 24 h of incubation, ACTH alone had no effect on steroidogenic enzymes but, while combined with androstenedione, it further decreased 21-hydroxylase activity and stimulated 17-hydroxylase and 17,20-lyase activities. Cortisol, corticosterone, oestradiol and 11β-hydroxy androstenedione had no effect on steroidogenic enzyme activities while the inhibitory effect on 21-hydroxylase activity was only observed with androstenedione, testosterone and dihydrotestosterone. Addition of hydroxyflutamide, a pure antiandrogen, did not block the inhibitory effect of androstenedione on 21-hydroxylase and 11-hydroxylase activities. The reduction in oxygen tension from 19 to 2% which was aimed at examining the oxygen-mediated effects on steroidogenic enzymes, revealed that the reduction in 21-hydroxylase activity induced by androstenedione could not be prevented by low oxygen tension. An interaction of C19 steroids at the level of the enzymes is also suggested by our finding that androstenedione had no effect on basal and ACTH-stimulated steady-state 11-hydroxylase, 17-hydroxylase, 17,20-lyase and 21-hydroxylase mRNA levels. These results indicate that C19 steroids alter the adrenal steroidogenic enzyme activities in such a manner that C19 steroid synthesis is increased while glucocorticoid production is inhibited. The mechanism of action of C19 steroids does not involve gene expression for steroidogenic enzymes but probably a direct interaction with steroidogenic enzymes, namely 21-hydroxylase, 17-hydroxylase and 17,20-lyase. Our data suggest that C19 steroids may reduce the amount of 21-hydroxylase in the microsomal fraction which may have a major impact on the levels of microsomal P450 reductase available for 17-hydroxylase and 17,20-lyase activities. Journal of Endocrinology (1992) 132, 269–276

Diurnal variation and melatonin induction of hepatic molybdenum hydroxylase activity in the guinea-pig

1989 ◽  
Vol 38 (9) ◽  
pp. 1459-1464 ◽  
Author(s):  
Christine Beedham ◽  
David J. Padwick ◽  
Youseff Al-Tayib ◽  
John A. Smith
Keyword(s):  
Guinea Pig ◽  
Diurnal Variation ◽  
Hydroxylase Activity

scholarly journals Effect of oestrogen and 1,25-dihydroxycholecalciferol on 25-hydroxycholecalciferol metabolism in primary chick kidney-cell cultures

1978 ◽  
Vol 174 (1) ◽  
pp. 231-236 ◽  
Author(s):  
E Spanos ◽  
D I Barrett ◽  
K T Chong ◽  
I MacIntyre
Keyword(s):  
Vitamin D ◽  
Cell Cultures ◽  
Kidney Cell ◽  
Primary Cultures ◽  
Kidney Cells ◽  
Hydroxylase Activity ◽  
Experimental Conditions ◽  
Polar Metabolites ◽  
Chick Kidney ◽  
25 Hydroxycholecalciferol

Primary cultures of chick kidney cells convert 25-hydroxycholecalciferol into more-polar metabolites. Cells from vitamin D-deficient chicks have high 25-hydroxycholecalciferol 1 alpha-hydroxylase (1 alpha-hydroxylase) activity, but no 25-hydroxycholecalciferol 24-hydroxylase (24-hydroxylase) activity. Physiological concentrations of 1,25-dihydroxycholeclaciferol suppress 1 alpha-hydroxylase and induce 24-hydroxylase activity. The inhibition of 1 alpha-hydroxylase preceded the induction of 24-hydroxylase. In contrast, oestradiol-17 beta had no effect on the activity of either hydroxylase under a variety of experimental conditions. These results clearly demonstrate that 1,25-dihydroxycholecalciferol, but not oestrogen, acts directly on the kidney cells to regulate the metabolism of 25-hydroxycholecalciferol.

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