[The metabolism of heavy metals depends on the vitamin-D status of the body]. / Obmen tiazhelykh metallov zavisit ot D-vitaminnogo statusa organizma.

The effect of vitamin D3 and its two metabolites 1,25(OH)2D3 and 24,25(OH)2D3 on the metabolism of heavy metals--Sr, Pb and Cd was studied. The experiments were carried out on chickens, the heavy metals were added to the chicken's ration. The results obtained demonstrated that vitamin D3 caused accumulation of those metals in tissues and their toxicity in organisms. When increasing the vitamin dose from 200 to 500 IU on 1 kg of ration that tendency was being heightened. On the three steroids which had been studied the metabolite 1,25(OH)2D3 displayed the greatest activity in accumulating metals in tissues, Pb in particular. The effect of 24,25(OH)2D3 on the indices being studied was comparable with that of vitamin D3.

[Effects of calcium on the course of strontium toxicosis]. / Vliianie kal'tsiia na techenie strontsievogo toksikoza.

Chronic intake of Sr for 20 days by chickens caused in them a delay in body mass increase and symptoms of rickets in spite of complete provision with vitamin D. There were low levels of Ca, P, enhanced activity of alkaline phosphatase in the serum, inhibited mineralization of bone tissue, reduced levels of vitamin D-dependent calcium-binding protein, Sr accumulation in various tissues. Enrichment with Ca of the chickens ration diminished the above signs of Sr toxicosis. It is suggested that a protective effect of Ca in chronic Sr toxicity may be due to more active discrimination of Sr against Ca in intestinal assimilation of these cations.

[24,25-Dihydroxyvitamin D3 modulates the effect of 1alpha-hydroxyvitamin D3 on B lymphocyte maturation in chickens]. / 24,25-Digidroksivitamin D3 moduliruet deistvie 1alpha-gidroksivitamina D3 na sozrevanie B-limfotsitov u tsipliat.

Patterns of calcium metabolism and maturation of lymphocytes in chicken Fabricius bursa were studied in presence of various doses of I alpha-hydroxy vitamin D3 and 24,25-dihydroxy vitamin D3 administered separately and at various combinations. 24,25(OH2)D3 was distinctly less effective in the antirickets activity as compared with I alpha (OH)D3. A decrease in mass of Fabricius bursa and inhibition of lymphocytes maturation within early steps were observed in the birds with rickets. A toxic dose of I alpha (OH)D3 caused pseudohypertrophy of Fabricius bursa. Small doses of these drugs administered simultaneously exhibited higher effect both on rickets and on stimulation of B lymphocytes maturation. 24,25(OH)2D3 attenuated the negative effect of either subtoxic (0.65 nmol/day) or toxic (1.3 nmol/day) doses of I alpha (OH)D3 on an increase in body mass, calcemia, ash content of bones, content of small lymphocytes in Fabricius bursa.

[Effect of strontium on the anti-rickets activity of vitamin D3 and its hydroxy analogs]. / Deistvie strontsiia na antirakhiticheskuiu aktivnost' vitamina D3 i ego gidroksilirovannykh analogov.

Antirickets activity of vitamin D3 and of its derivatives 1 alpha- and 25-hydroxy vitamin D3 1.25- and 24,25-dihydroxy vitamin D3 and 1,24,25-trihydroxy vitamin D3 was studied in chicken maintained on a diet containing various amount (0.01-2.40 mg) of strontium. Vitamin D3 as well as its 24-hydroxy and 24,25-dihydroxy derivatives lost their antirickets activity in presence of high strontium concentrations. Under the same conditions I alpha-hydroxy, 1,25-dihydroxy and 1,24,25-trihydroxy vitamins D3 retained the ability both to induce calcium-binding protein synthesis in intestinal epithelium and to stimulate bone tissue mineralization, although to a lesser degree as compared with controls, kept on strontium-free diet. These results suggest that presence of I alpha-OH-group in the steroid molecule is necessary for expression of maximal biological activity under conditions of elevated strontium content in diet while the activity of hydroxylase is inhibited in kidney. At the same time, the vitamin D3 derivatives containing the OH-group are responsible for impairments caused by increased accumulation of strontium.

[Evaluation of the vitamin D activity of yeasts with altered sterol metabolism]. / Otsenka D-vitaminnoi aktivnosti shtammov drozhzhei s izmenennym metabolizmom sterinov.

The sterol content of Saccharomyces strains with altered ergosterol metabolism was studied by UV-spectrophotometry, thin-layer chromatography and chromatographic mass-spectroscopy. A technique for estimation of D-vitamin activity of the yeast strains is proposed. The irradiated biomass of the strains accumulated ergosta-5,7-dien-3 beta-ol and also cholesta-5,7,24-trien-3 beta-ol and cholesta-5,7,22,24-tetraen-3 beta-ol is characterized by high antirachitic activity.

[Participation of the goblet cells of the small intestine in the excretion of Fe, Zn and Pb cations]. / Uchastie bokalovidnykh kletok tonkogo kishechnika v ékskretsii kationov Fe, Zn i Pb.

A comparative study of the excess of Zn, Fe and Pb on the amount of goblet cells (GC) and localization of these cations in the chick small intestine epithelium was carried out. In chicks with additional dose of Zn (2 g/kg) and Pb (0.2 g/kg), compared to control chicks the amount of GC in the epithelium of various intestinal parts increased by 1.5-1.8 times. Under a high dose of Pb (2.0 g/kg), the amount of GC increased by 3-4 times, and degenerative changes in the epithelium were observed. A histochemical electron microscopical study of duodenal sections revealed an accumulation of Fe, Zn and Pb within GC and in their excretion, in addition to brush border and glycocalyx. The involvement of intestinal GC in cation excretion is proven.

Vitamin-A-dependent zinc-binding protein and intestinal absorption of Zn in chicks.

It was demonstrated that the development of experimental avitaminosis A in chicks led to secondary zinc deficiency. The balance of Zn in the chick became negative, while the Zn content of various tissues decreased. Thus in vitamin-A-deficient chicks the serum Zn content was 1258 (SD 26.3) micrograms/l which was considerably lower than 1652 (SD 97.8) micrograms/l in controls. Zn absorption was considerably reduced throughout the entire small intestine of vitamin-A-deficient chicks and most markedly in the ileal region. Within 72 h after retinyl acetate administration Zn absorption was fully restored in this region of the intestine. The 65Zn-binding capacity of soluble proteins, present in the supernatant fraction of ileal-mucosa homogenates of vitamin-A-deficient chicks, was found to increase 2.6 times by 72 h after the administration of a single dose of retinyl acetate. A vitamin-A-dependent Zn-binding protein (ZnBP), absent in vitamin-A-deficient chicks, was isolated from the ileal mucosa after their repletion with vitamin A. Competitive-binding studies (calcium, cadmium, copper) showed the protein to be highly specific for Zn ions. The molecular weight of ZnBP was 83 kDa. The association constant of the protein-Zn complex was 0.8 X 10(6)/mol. The protein was acidic with approximately 20% of its amino acid residues belonging to dicarboxylic acids. ZnBP was found to be a glycoprotein, and it contained hexose as a carbohydrate component. It is suggested that ZnBP is involved in the binding of Zn in the ileal mucosa of chicks.

[Effect of vitamin D on inorganic phosphorus transport and alkaline phosphatase activity of the small intestine of chickens]. / Deistvie vitamina D na transport neorganicheskogo fosfora i aktivnost' shchelochnoi fosfapazy v tonkoi kishke tsypliat.

Effect of vitamin D on the intensity of inorganic phosphorus absorption and the activity of unspecific alkaline phosphatase in the shick small intestine was studied in vitro on everted gut sacks. Repletion of rachitic chicks with vitamin D3 (500 IU) 72 hrs prior to decapitation enhanced the transport rate 3.5-fold. Concomitantly, the activity of alkaline phosphatase increased 1.8-fold. Analysis of the data obtained shows the important role that the interaction of alkaline phosphatase and inorganic phosphorus transport plays in phosphorus absorption from sources of organic nature.

Absence of alkaline phosphatase-linked inorganic phosphate transport in the chick jejunum.

The role of non-specific alkaline phosphatase-linked inorganic phosphate (Pi) transport in the chick jejunum was investigated by using the everted gut sac technique. The highest intensity of transport was observed for free Pi. The maximal transport rate was considerably reduced when beta-glycerophosphate was used as a single source of phosphorus. These results suggested absence of the alkaline phosphatase-linked transport system for inorganic phosphate in the epithelium of the chick jejunum. Studies of Mg effect on Pi absorption as well as examination of temporal changes in Pi transport rate and beta-glycerophosphate hydrolysis rate by intestinal brush border alkaline phosphatase gave further backing to this suggestion.

[Role of goblet enterocytes in the intestinal excretion of calcium]. / Rol' bokalovidnykh énterotsitov v kishechnoi ékskretsii kal'tsiia.

A comparative study on the amount of goblet cells and excretion of endogenic calcium in the small intestine of chicks has been made. The amount of goblet cells (per brush area unit) significantly increased at the deficiency of vitamin D3 as well as at the surplus of calcium in the diet. Excretion intensity of endogenic calcium (determined by 45Ca) correlates directly with the amount of goblet cells. Histochemical and electron microscopical investigations show that precipitate accumulations containing calcium are absorbed in goblet cells and their secret on the surface of the cells. The significance of goblet cells in the intestinal excretion of endogenic calcium is discussed.

[Effect of vitamin D on lead assimilation]. / Vliianie vitamina D na usvoenie svintsa.

It was established in experiments on rickety chickens given and not given an additive of 0.5% lead acetate to the diet and vitamin D3 (10 IU/day intramuscularly) for a week that vitamin D induced an appreciable increase of lead deposition in the tissues. The degree of lead poisoning assessed according to the content of delta-aminolevulinic acid in red cells was 8 times as increased as compared with the same indicator in chickens not injected with vitamin D. The balance studies demonstrated that retention of the diet lead under the effect of vitamin D rose 2 times. Vitamin D noticeably stimulated 210Pb absorption from chicken duodenum in experiments in situ.

Vitamin D3 and 1,25-dihydroxyvitamin D3 stimulate the skeletal muscle-calcium mobilization in rachitic chicks.

The Ca content in skeletal muscle relative to vitamin D3 intake was studied in chicks. It was found that the Ca content in rachitic chick muscle was significantly higher than normal and it decreased with vitamin D3 treatment. In 4-week-old chicks fed a vitamin D-deficient diet, the Ca content in leg muscle reached 9.86 +/- 1.07 mg/100 g wet wt, although in chicks receiving vitamin D3 in doses of 100 and 500 IU/kg diet, it was 7.80 +/- 0.72 and 6.08 +/- 0.61 mg/100 g wet wt, respectively. A single i.m. dose of 0.50 micrograms of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) or vitamin D3 caused a dramatic decrease in the muscle Ca content by 3 to 6 h after the injection. A simultaneous rise in the Ca level in blood serum was observed. However, at this time the Ca binding protein content in duodenal mucosa and the stimulation of Ca absorption were negligible. These findings allow the conclusion that the vitamin D deficiency in chicks leads to a surplus Ca accumulation in skeletal muscle. The administration of vitamin D3 or its metabolites causes rapid Ca release during the first 6 h. This may be the source of the Ca level increase in blood serum. In this respect 1,25(OH)2D3 was much more effective than vitamin D3.

[Vitamin D, calcium-binding protein and calcium absorption in the intestines]. / Vitamin D, kal'tsiisviazyvaiushchii belok i absorbtsiia kal'tsiia v kishechnike.

The author presents his own and literature data concerning the action of vitamin D and its analogs on the biosynthesis of calcium-binding protein (CaBP) in the chick intestinal mucosa. The mechanism of involvement of this protein in calcium transport across the intestinal epithelium is discussed. CaCP is considered as a specific test-substance for vitamin D. A close correlation between the CaCP content in the intestinal mucosa and the vitamin antirachitic effect is demonstrated. The quantitative estimates of the biological activity of various forms of vitamin D, their metabolites and synthetic analogs with respect to the CaCP content are given.

[Comparative antirachitic activity of 1,25-dihydroxyvitamin D3 and 1 alpha-hydroxyvitamin D3 in the chick]. / Sravnenie antirakhiticheskoi aktivnosti 1,25-dioksivitamina D3 i 1 alpha-oksivitamina D3 u tsypliat.

1,25-dihydroxy vitamin D3 and its synthetic analogue 1 alpha-hydroxy vitamin D3 were administered into chicken at the doses of 0.025, 0.05 and 0.1 micrograms per day within 25 days. Effect of the vitamins was estimated by a net gain of biomass, by biochemical alterations in blood, synthesis of calcium-binding protein, relative mass of parathyroid glands and by content of inorganic residue in bone tissue. Both vitamin preparations exhibited similar antirickety activity.

[Relations between the supply of vitamin D and accumulation of Pb in chickens]. / Otlozhenie Pb v organizme tsypliat v zavisimosti ot obespechennosti vitaminom D.

Lead accumulation in the body of 25-day-old chickens was studied depending on the dose of lead and the presence of vitamin D in the diet. It was found that with the increase of the dose of lead (40, 100 and 200 mg/kg feed), its level in the blood, bones, kidneys and liver grows. Introduction of vitamin D in the diet (500 IU per kg) considerably raises the content of lead in the blood (from 212 to 284 micrograms/100 ml) in bone tissues (from 29.4 to 242.7 mg per g dry substance). Single injection of vitamin D to rachitic chickens also promotes lead accumulation in the tissues. Thus a conclusion may be drawn that vitamin D stimulates lead accumulation.

[Comparative antirachitic activity of vitamins D2 and D3 in the body of chicks]. / Sravnitel'naia antirakhiticheskaia aktivnost' vitaminov D2 i D3 v organizme tsypliat.

In the four-week study the antirachitic action of vitamin D2 in different does (5000, 7500, 10 000 I. U. per kg food) and of vitamin D3 in a dose of 500 I. U. per kg food was investigated in chicks. The vitamin efficiency was measured with respect to the following seven parameters: weight gain, serum content of Ca and P, serum activity of alkaline phosphatase, bone ash content, content of Ca-binding protein in the duodenal mucosa, and weight of parathyroid glands. In regard to these parameters, vitamin D2 in a dose of 7500 I. U./kg and vitamin D3 in a dose of 500 I.U./kg produced a similar effect. Thus, the antirachitic effect of vitamin D3 was 15 times higher than that of vitamin D2. In the three-day study of the effect of vitamins D2 and D3 on the synthesis of Ca-binding protein it was found that they exerted a similar effect when the dose of vitamin D2 was 14.5 times higher than that of vitamin D3.