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D B Endres

Publications and source records attributed to D B Endres.

24 records · Page 2Linked to original sources
PubMed1986

Circulating parathyroid hormone concentrations in normal and vitamin D-deprived rat pups determined with an N-terminal-specific radioimmunoassay.

Plasma PTH concentrations were determined in rats with an antiserum to human PTH (1-34) that cross reacts with rat PTH in order to evaluate the effects of growth, vitamin D deficiency and dietary modulations of plasma calcium. Displacement curves for synthetic rat PTH (1-34) and diluted rat plasma were parallel with curves for the hPTH (1-34) standards and hPTH (1-84). Parathyroidectomy in 33-day-old rats resulted in a fall in iPTH from (mean +/- SE) 8.1 +/- 0.5 to 5.4 +/- 0.5 pg/ml in an assay in which the lowest detectable concentration was 3 pg/ml. Elevation of plasma Ca by 0.7 mg/dl by dietary calcium supplementation in 25-day-old pups led to a plasma iPTH level of 4.4 +/- 0.7 pg/ml compared with 9.9 +/- 0.7 pg/ml in controls. There were no significant changes in iPTH in control rats fed a complete diet containing 0.4% Ca and 0.4% P over the age range 14-56 days. Rat pups (-D) suckling vitamin D-deprived mothers had plasma Ca and iPTH values of 7.76 +/- 0.16 mg/dl and 173 +/- 27 pg/ml, respectively, at 25 days of age and 5.8 +/- 0.2 mg/dl and 677 +/- 85 pg/ml, respectively, at 56 days. The -D pups that had access to their mothers' calcium-supplemented diet (1.6% Ca and 1.4% P) had a mean plasma Ca value that was 0.5 mg/dl above that of the control group and a mean plasma iPTH level of 6.7 +/- 0.8 pg/ml. We suggest that the RIA for PTH measures mostly, if not entirely, bioactive PTH. We conclude that plasma iPTH (a) remains essentially unchanged in normal rats during the rapid growth period, (b) can increase up to 75-fold in hypocalcemic vitamin D-deficient rats, and (c) can be suppressed to barely detectable levels when plasma Ca is raised less than 1 mg/dl above the level of normal control rats.

Age Factors↗
PubMed1985

Estrogen and progestin effects on urinary calcium and calciotropic hormones in surgically-induced postmenopausal women.

Seventeen surgically-induced postmenopausal (PM) women were randomized to receive either 0.625 mg of conjugated estrogens (CE) daily or 150 mg of intramuscular depomedroxyprogesterone acetate (DMPA) every 3 months. Urinary calcium/creatinine ratios were significantly higher than ratios of premenopausal controls before treatment, but were lower in all patients 2 months after both types of treatment. Compared to controls, all PM patients had similar levels of serum PTH and 25 hydroxy vitamin D before and after treatment. As a group, PM patients had lower levels of 1.25-dihydroxyvitamin D. In 5 patients who had levels which were below the normal range, 3 were treated with CE and 2 received DMPA. These patients all had significant increases in 1,25-dihydroxyvitamin D after treatment. Serum calcitonin did not change with either CE or DMPA treatment. These data suggest that, while both CE and DMPA lower calcium excretion in PM women, the mechanism(s) for the effects of hormonal treatment on bone resorption remain unsettled.

Adult↗
PubMed1985

Low serum concentrations of 1,25-dihydroxyvitamin D in human magnesium deficiency.

The effect of magnesium deficiency on vitamin D metabolism was assessed in 23 hypocalcemic magnesium-deficient patients by measuring the serum concentrations of 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D [1,25-(OH)2D] before, during, and after 5-13 days of parenteral magnesium therapy. Magnesium therapy raised mean basal serum magnesium [1.0 +/- 0.1 (mean +/- SEM) mg/dl] and calcium levels (7.2 +/- 0.2 mg/dl) into the normal range (2.2 +/- 0.1 and 9.3 +/- 0.1 mg/dl, respectively; P less than 0.001). The mean serum 25OHD concentration was in the low normal range (13.2 +/- 1.5 ng/ml) before magnesium administration and did not significantly change after this therapy (14.8 +/- 1.5 ng/ml). Sixteen of the 23 patients had low serum 1,25-(OH)2D levels (less than 30 pg/ml). After magnesium therapy, only 5 of the patients had a rise in the serum 1,25-(OH)2D concentration into or above the normal range despite elevated levels of serum immunoreactive PTH. An additional normocalcemic hypomagnesemic patient had low 1,25-(OH)2D levels which did not rise after 5 days of magnesium therapy. The serum vitamin D-binding protein concentration, assessed in 11 patients, was low (273 +/- 86 micrograms/ml) before magnesium therapy, but normalized (346 +/- 86 micrograms/ml) after magnesium repletion. No correlation with serum 1,25-(OH)2D levels was found. The functional capacity of vitamin D-binding protein to bind hormone, assessed by the internalization of [3H]1,25-(OH)2D3 by intestinal epithelial cells in the presence of serum was not significantly different from normal (11.42 +/- 1.45 vs. 10.27 +/- 1.27 fmol/2 X 10(6) cells, respectively). These data show that serum 1,25-(OH)2D concentrations are frequently low in patients with magnesium deficiency and may remain low even after 5-13 days of parenteral magnesium administration. The data also suggest that a normal 1,25-(OH)2D level is not required for the PTH-mediated calcemic response to magnesium administration. We conclude that magnesium depletion may impair vitamin D metabolism.

Calcifediol↗
PubMed1979

Sex differences in the concentrations of glucocorticoid receptors in rat liver and thymus.

The effects in rats of adrenalectomy, hypophysectomy, ovariectomy or combinations of these operations on the concentrations of glucocorticoid receptors in the cytosol of liver and thymus were measured. The concentrations of glucocorticoid receptors were lower in cytosols from liver and thymus of female than of male rats. After adrenalectomy, there was a significant increase in the concentrations of receptors measured in the cytoplasm from the liver and thymus of female rats and from the liver of male rats. After adrenalectomy or hypophysectomy, there was no sex difference in the concentration of glucocorticoid receptors in cytosols of liver or thymus. After ovariectomy, the concentration of receptors in cytosols from the thymus, but not from the liver, increased. Ovariectomized rats responded to adrenalectomy in the same way as intact male rats. The different responses shown by male and female rats to endocrine manipulation probably depend upon associated changes in plasma corticosterone concentrations which are influenced by the ovary. Differences in response between the liver and thymus probably reflect a preferential distribution of corticosterone to the liver rather than to the thymus.

Adrenalectomy↗
PubMed1978

A solid-phase radioimmunoassay for vitamin B12 in serum, with use of radioiodinated tyrosine methyl ester of vitamin B12.

Although radioassays for vitamin B12 with use of any of several binding proteins have been available for many years, a radioimmunoassay for B12 has not been reported. We describe here such a radioimmunoassay, incorporating, for the first time, a radioiodinated tyrosine methyl ester of B12 as the radioactive tracer. Polypropylene tubes are coated with antiserum raised in a rabbit against B12/bovine serum albumin to simplify the separation of bound and free radioactivity. Factors affecting the preparation of coated tubes are described. The assay is accurate, sensitive, precise, and specific for vitamin B12. Accuracy of the assay is unaffected by the presence of denatured protein. The advantages of this radioimmunoassay over conventional radioassays are discussed.

Female↗