Differential effects of vitamin D receptor activators on aortic calcification and pulse wave velocity in uraemic rats.

BACKGROUND: Vascular calcification is associated with an increase in cardiovascular mortality in stage 5 chronic kidney disease. To determine if vitamin D receptor activators (VDRAs) have differential effects in the pathogenesis of aortic calcification, we assessed the effects of paricalcitol and doxercalciferol in vivo using 5/6 nephrectomized (NX) rats. To quantify the functional consequences of vascular calcification, pulse wave velocity (PWV), an aortic compliance index, was measured. METHODS: NX rats were fed a diet containing 0.9% phosphorous and 0.6% calcium 4 weeks prior to and throughout the study. On Day 0, rats received vehicle or VDRA (0.083, 0.167 and 0.333 microg/kg, i.p.) three times per week for 6 weeks. At Day 0 and Weeks 2 and 6, blood was drawn and PWV was measured by Doppler ultrasound. RESULTS: VDRAs (0.167 and 0.333 microg/kg) consistently lowered PTH at Weeks 2 and 6. All doses of paricalcitol increased serum calcium at Week 6 but not at Week 2, while the two higher doses of doxercalciferol increased serum calcium at both Weeks 2 and 6. Treatment with paricalcitol (0.333 microg/kg) increased serum phosphorus at Weeks 2 and 6; these changes were not different from those observed in 5/6 NX rats. All doses of doxercalciferol increased serum phosphorus at Week 6. Paricalcitol had no effect on Ca x P; however, the two highest doses of doxercalciferol increased Ca x P at Weeks 2 and 6 above that observed in the 5/6 NX vehicle-treated group. There were no differences in aortic calcium and phosphorus contents at the end of 6 weeks among SHAM-, 5/6 NX- and paricalcitol-treated rats. However, treatment with the two higher doses of doxercalciferol caused a significant elevation in aortic calcium and phosphorus contents. Measurements of PWV demonstrated differential effects of VDRAs on vascular compliance. Paricalcitol produced no effects on PWV, while the two highest doses of doxercalciferol increased PWV at Week 6. CONCLUSIONS: In uraemic rats with established secondary hyperparathyroidism, we demonstrate differential effects of paricalcitol and doxercalciferol on aortic calcification and PWV, independent of serum Ca, P and Ca x P, suggesting different mechanisms of action between VDRAs.

Phase II study of 1alpha-hydroxyvitamin D(2) in the treatment of advanced androgen-independent prostate cancer.

PURPOSE: In this single institution Phase II trial, we evaluated the efficacy of the vitamin D analogue, 1alpha-OH-D(2), in patients with advanced hormone-refractory prostate cancer. EXPERIMENTAL DESIGN: The patients initially received 1alpha-OH-D(2) at 12.5 micro g p.o. every day, which was dose adjusted for hypercalcemia. Given the cytostatic nature of the drug, the primary study end point was progression-free survival for a minimum of 6 months. The secondary end point was further characterization of drug toxicity. RESULTS: A total of 26 patients was enrolled. Using the intent-to-treat population, stable disease was seen for an average of 19.2 weeks (median 12 weeks, range 3-108 weeks). Twenty patients were evaluable for response. The one patient that achieved disease stabilization for >2 years elected to come off-study because of patient preference. His last disease evaluation showed no evidence of progression. No objective responses were seen. Previous and ongoing clinical observations strongly imply that PSA could be a misleading surrogate marker for clinical effect with this type of drug. Therefore, prostate-specific antigen was not used as a marker for disease response. Toxicity was as expected with mild hypercalcemia and associated symptoms like constipation and prerenal azotemia seen in some patients. Six (30%) evaluable patients experienced stable disease for >6 months, suggesting possible cytostatic activity. CONCLUSION: The results of this and other trials suggest further clinical investigation in this disease with vitamin D analogues alone or in combination with other agents, such as chemotherapy, should be pursued.

1alpha-hydroxyvitamin D2 is less toxic but not bone selective relative to 1alpha-hydroxyvitamin D3 in ovariectomized rats.

Identification of bone selective vitamin D analogues would provide an interesting substance class for the treatment of osteoporosis. The synthetic prodrug 1alpha-hydroxyvitamin D2 [1alpha(OH)D2] has been shown to combine equal bone-preserving activity with distinctly reduced calcemic effects relative to 1alpha-hydroxyvitamin D3 [1alpha(OH)D3] in 3-month-old ovariectomized (OVX) rats. Therefore, 1alpha(OH)D2 may be a bone-selective compound. The aim of this study was to compare the bone protective and the calcemic activities of chronically administered 1alpha(OH)D2 and 1alpha(OH)D3 in 6-month-old OVX rats over a broad dose range from ineffective to toxic doses. Ninety-six female 6-month-old Fischer-344 rats were used for this experiment. Eighty rats were bilaterally OVX, 8 rats were sham-operated (SHAM), and 8 rats were killed at the time of surgery as a baseline control. Groups of OVX rats received vehicle alone (n = 16) or daily doses in the diet of 0.025, 0.05, 0.1, and 0.2 microg of 1alpha(OH)D2 or 1alpha(OH)D3 per kg body weight (BW) per day (n = 8 each). After calcein double-labeling, all animals were killed 3 months post-OVX. Orally administered 1alpha(OH)D2 was significantly less toxic compared with 1alpha(OH)D3 in terms of BW gain and kidney calcium content. The effects of 1alpha(OH)D2 and 1alpha(OH)D3 on serum calcium and urinary calcium excretion were generally similar at all doses in this study. Both 1alpha(OH)D2 and 1alpha(OH)D3 prevented the estrogen deficiency-induced bone loss in OVX rats, and induced profound bone anabolic effects at high dosages. 1alpha(OH)D3 and 1alpha(OH)D2 also dose-dependently increased total bone mineral density (BMD), cortical area, and cortical thickness in the tibial diaphysis of OVX rats. Bone resorption as assessed by osteoclast numbers (Oc.Ns) in vertebral cancellous bone and urinary excretion of deoxypyridinoline (DPD) was dose-dependently suppressed by 1alpha(OH)D2 and 1alpha(OH)D3. These data show that although 1alpha(OH)D2 was slightly but significantly less toxic compared with 1alpha(OH)D3, it did not have increased skeletal effects at any dose. Taken together, our findings argue against selective metabolic activation of 1alpha(OH)D2 in bone.

Toxicity and dose-response studies of 1alpha-hydroxyvitamin D2 in a retinoblastoma xenograft model.

BACKGROUND: Although calcitriol (1,25-dihydroxycholecalciferol) and vitamin D(2) inhibit retinoblastoma growth in the athymic (nude) mouse xenograft (Y-79 cell line) model of retinoblastoma, they can cause severe toxicity. OBJECTIVE: To examine the toxicity of and dose-dependent response for the inhibition of tumor growth for 1alpha-hydroxyvitamin D(2) (1alpha-OH-D(2)), an analogue with reduced systemic toxicity, in the athymic Y-79 mouse model. METHODS: Mice were randomized into treatment and control groups for 5-week toxicity and dose-response studies. Treatment was via oral gavage 5 times per week. Dose-response studies measured tumor inhibition and drug serum levels. Tumor size and body weight were measured weekly together with various criteria for toxicity. Animals were euthanized at the end of the treatment period. Tumors and kidneys were harvested, and serum was analyzed for calcium and drug levels. RESULTS: Doses of 0.1 to 1.2 microg/d were selected on the basis of toxicity studies for the dose-response trial. Tumor weight and volume in the 0.2-microg and 0.3-microg doses were significantly lower than in controls. Mortality rates and kidney calcification in mice treated with doses of 0.1 to 0.3 microg were lower than those observed in studies of calcitriol and vitamin D(2). CONCLUSION: A vitamin D analogue, 1alpha-OH-D(2), inhibits tumor growth in this xenograft model of retinoblastoma with less toxicity than calcitriol and vitamin D(2).

Effectiveness of 1alpha-hydroxyvitamin D2 in inhibiting tumor growth in a murine transgenic pigmented ocular tumor model.

OBJECTIVE: To study the effectiveness of the vitamin D analogue 1alpha-hydroxyvitamin D(2) (1alpha-OH-D(2)) in inhibiting ocular tumor growth in transgenic "Tyr-Tag" mice that developed pigmented ocular tumors produced with the simian virus 40 T and t antigens under the control of the mouse tyrosinase gene. These animals develop pigmented intraocular tumors primarily from the retinal pigment epithelium that closely resemble the histologic features and growth pattern of human choroidal melanoma. METHODS: A total of 73 Tyr-Tag transgenic mice between 6 and 7 weeks old were randomly assigned by sex and litter to 3 treatment groups to receive 0.05 microg/d, 0.1 microg/d, or 0.2 microg/d of 1alpha-OH-D(2); a control group received vehicle (coconut oil). The drug was administered by oral gavage 5 times a week for 5 weeks. The animals were then euthanized and their eyes were enucleated and processed histologically. Three serial sections from each eye were examined microscopically and the mean tumor area measured using Optimus software version 6.5 (Media Cybernetics LP, Silver Spring, Md). Toxic adverse effects were assessed on the basis of mortality, weight loss, and serum calcium levels. RESULTS: The mean tumor size in the 0.1- microg/d and 0.2- microg/d dose groups was smaller than in the controls (P<.001). No significant difference was seen between the 0.05- microg/d dose group and the control group (P =.64). Survival for the 0.1- microg/d and 0.2- microg/d dose groups was lower than for the controls (95% in the controls vs 85.7% and 73.7%, respectively; P<.01). CONCLUSION: In the Tyr-Tag transgenic mouse, 1alpha-OH-D(2) inhibits pigmented ocular tumor growth at moderate drug levels with relatively low mortality. Clinical Relevance Vitamin D analogues merit further preclinical study in the treatment of ocular melanoma.

Effectiveness of vitamin D analogues in treating large tumors and during prolonged use in murine retinoblastoma models.

OBJECTIVE: To investigate the effectiveness of the vitamin D analogues 1,25-(OH)(2)-16-ene-23-yne vitamin D(3) (16,23-D(3)) and 1alpha-hydroxyvitamin D(2) (1alpha-OH-D(2)) in inhibiting retinoblastoma growth in large tumors in a xenograft model and with prolonged use in a transgenic model. METHODS: For the large-tumor study, the xenograft athymic mouse/human retinoblastoma cell (Y-79) model was used. Subcutaneous tumors were allowed to grow to an average volume of 1600 mm(3). Systemic treatment with 1 of the vitamin D analogues or with vehicle (control groups) was carried out for 5 weeks. For the long-term study, transgenic beta-luteinizing hormone-large T antigen (LHbeta-Tag) mice were systemically treated with 1 of the 2 compounds or vehicle (control groups) for up to 15 weeks. Tumor size and signs of toxicity were assessed. RESULTS: In the large-tumor study, tumor volume ratios for the 1alpha-OH-D(2) and 16,23-D(3) groups were significantly lower than those for controls (P<.002). No significant differences in tumor volume were seen between the 1alpha-OH-D(2) and 16,23-D(3) groups (P =.15). In the long-term study, the 1alpha-OH-D(2) group showed significantly smaller tumor size compared with its control (P<.001). No significant difference was seen between the 16,23-D(3) group and its control. Some toxic effects related to hypercalcemia were seen in both studies. CONCLUSIONS: In athymic mice in the large-tumor study, both 1alpha-OH-D(2) and 16,23-D(3) were effective in inhibiting tumor growth compared with controls. In the long-term study, 1alpha-OH-D(2) inhibited tumor growth but 16,23-D(3) did not. Effective doses of both compounds caused hypercalcemia and a significant increase in mortality. Clinical Relevance Use of 1alpha-OH-D(2) inhibited tumor growth in large tumors and with long-term treatment compared with controls. Because of hypercalcemia-related toxic effects seen in the present experiments, in clinical trials, serum calcium levels should be carefully monitored. This analogue may require use with drugs that lower serum calcium levels or use of relatively lower doses or skipped doses. The ideal alternative solution would be to identify vitamin D analogues that retain the antineoplastic action without the calcemic activity.

The novel analog 1,24(S)-dihydroxyvitamin D2 is as equipotent as 1,25-dihydroxyvitamin D3 in growth regulation of cancer cell lines.

The physiologically active metabolite of the vitamin D seco-steroid hormone, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), is a major regulator of mineral homeostasis. Recent evidence also suggests its role in regulating proliferation and differentiation of cells, including cancer cells. Therapeutic application of 1,25(OH)2D3 to hyperproliferative disease, such as cancer, is thwarted by its hypercalcemic activity. To overcome this problem, analogs of 1,25(OH)2D3 have been produced which retain growth regulating properties and exhibit decreased hypercalcemic activity. In the present study, the efficacy of the vitamin D2 analog, 1,24(S)-dihydroxyvitamin D2 (1,24(S)-(OH)2D2) in the inhibition of cancer cell proliferation and in inducing differentiation of cancer cells was compared to that of 1,25(OH)2D3. By the [3H]-thymidine incorporation procedure, 1,24(S)-(OH)2D2 is as equipotent as 1,25(OH)2D3 in inhibiting the proliferation of five different cell lines, ROS 17/2.8, the rat osteosarcoma cell line, MCF-7, the human breast cancer cell line, HD-11, the chick bone marrow v myc transformed cell line, HT-29, the human colon cancer cell line and HL-60, the human leukemia cell line. The inhibitory action was dose and time-dependent. The NBT reduction method indicated that 1,24(S)-(OH)2D2 induces the differentiation of the human leukemia cell (HL-60) to the same extent as 1,25(OH)2D3. Notwithstanding the vast similarity between 1,24(S)-(OH)2D2 and 1,25(OH)2D3 with regard to the above activities, they differ in their effects on calcium regulation. In conclusion, the present results encourage the use of 1,24(S)-(OH)2D2 for the treatment of cancer disease in vivo.

A large dose of ergocalciferol does not cause deficient blood coagulation but is extremely toxic to rats.

Male Jcl:SD rats were fed vitamin D2 (ergocalciferol) at levels of 0 (control), 0.39, 0.63 and 1.00% or 0 (control), 0.0195, 0.0315 and 0.050% in the diet for 7 days. All rats of the 0.39-1.00% groups expired on days 2 and 3, while some rats of the 0.0195-0.050% groups died on days 3-6. LD50 (median lethal 7-day cumulative dose calculated from food intake) is 110.5 mg/kg (0.0354% dietarily). In expired and surviving treated rats, several organs (kidney, heart, etc.) were found to be mineralized; there were also renal tubular injuries and pulmonary bleeding. Centrilobular necrosis of liver was detected only in dead rats. Treatment also caused hypercalcemia but did not decrease blood coagulation factors. These results suggest that vitamin D does not have the effect of impeding blood coagulation but that it is extremely toxic, probably due to the hypercalcemia it causes.

Metabolism of [3alpha-3H] 25-hydroxyvitamin D2 in kidneys isolated from normal and vitamin D2-intoxicated rats.

With the availability of A-ring labelled 25OHD2, [3alpha-3H] 25OHD2, we have performed the present study to examine the metabolism of 25OHD2 using physiological substrate concentrations in perfused kidneys isolated from both normal and vitamin D2-intoxicated rats. Our results indicate that [3alpha-3H] 25OHD2 is metabolized into both 24(S),25,28-trihydroxyvitamin D2 [24(S),25,28(OH)3D2] and 24(R),25,26-trihydroxyvitamin D2 [24(R), 25,26(OH)3D2], and the amounts of these two metabolites produced in the kidney of vitamin D2-intoxicated rat were about 3-5 times higher than those produced in the kidney of normal rat. Similar results were also obtained with rat kidney homogenates incubated with [3alpha-3H] 25OHD2. Furthermore, we noted that the production of both 24(S),25,28(OH)3D2 and 24(R),25,26(OH)3D2 in the kidney homogenates of vitamin D2-intoxicated rats increased with the time of incubation and then subsequently decreased. The decrease in both 24(S),25,28(OH)3D2 and 24(R),25,26(OH)3D2 coincided with an increase in the fraction of total radioactivity distributed in the aqueous phase of the kidney homogenates. This finding suggested the possibility of further metabolism of 24(S),25,28(OH)3D2 and 24(R), 25,26(OH)3D2 into polar water-soluble metabolite(s). We then measured the radioactivity in the aqueous phase of kidney homogenates of both normal and vitamin D2-intoxicated rats incubated with [3alpha-3H] 25OHD2. It was noted that the amount of radioactivity in the aqueous phase of kidney homogenates of vitamin D2-intoxicated rats is higher than that present in the aqueous phase of kidney homogenates of normal rats. Thus, our study provides evidence for the first time for the formation of both 24(S),25,28(OH)3D2 and 24(R),25, 26(OH)3D2 under physiological conditions, and the possibility of their further metabolism into as yet unidentified polar water-soluble metabolite(s). As the formation of all these metabolites is increased in the kidney of vitamin D2-intoxicated rats when compared to normal rats, it appears that the increased rate of metabolism of 25OHD2 during hypervitaminosis D2 plays a significant role in the deactivation of 25OHD2.

A lethal hypervitaminosis A syndrome in young monkeys (Macacus fascicularis) following a single intramuscular dose of a water-miscible preparation containing vitamins A, D2 and E.

Large intramuscular doses of a water-miscible preparation of vitamin A (500,000 I.U. retinyl acetate/ml), vitamin E (50 I.U./ml) and vitamin D2 (50,000 I.U./ml) were administered to young monkeys (Macacus fascicularis) weighing 1-1.8 kg. At vitamin A doses equivalent to 200 mg retinol/kg or higher, early signs of acute toxicity included yawning, apparent drowsiness, nausea and vomiting, head shaking, neck hyperextension, motor hyperactivity and coordination. These immediate signs were first noted 3-35 minutes after injection. Following apparent recovery at 1-2 hrs, longer term signs of toxicity, such as decreased activity, malaise, drowsiness, loss of appetite, loss of weight, and itchiness of the skin, appeared within 1-6 days, depending on the dose. Monkeys receiving the highest lethal doses became progressively weaker, showed labored breathing, lapsed into a coma, lost simple reflexes and then died. Respiratory failure usually preceded the cessation of heart beat. In some monkeys on a lower but lethal dose, death was preceded by generalized convulsive seizures. The time of onset of the first sign and survival time were inversely proportional to the dosage, but in individual monkeys no correlation existed between onset time and survival time. Female monkeys seemed to succumb faster to a lethal dose than male monkeys. All animals receiving the equivalent of 300 mg retinol/kg died. Under the conditions used, the LD50 was estimated to be 168 mg retinol (560 000 I>U.) per body weight.

Acute vitamin D3 toxicosis in horses: case reports and experimental studies of the comparative toxicity of vitamins D2 and D3.

Acute vitamin D toxicosis was diagnosed in 2 horses fed a grain ration containing 1,102,311 IU of cholecalciferol (vitamin D3)/kg (500,000 IU/lb) for about 30 days. Horse 1 died acutely with extensive mineralization of cardiovascular and other soft tissues. Horse 2, which had severe clinical signs and clinicopathologic changes of toxicosis, was treated with nonsteroidal antiinflammatory drugs and recovered in about 6 months. In an experimental study, the toxicity of ergocalciferol (vitamin D2) and cholecalciferol was compared in 2 horses (No. 3 and 4) given the respective vitamins at a daily dosage of 33,000 IU/kg of initial (day 0) body weight for 30 days. Except for slight loss in body weight (8%) during the 1st few days of treatment, horse 3 remained clinically normal. Horse 4 developed limb stiffness and tachycardia, became anorectic, weak, and recumbent, lost 29% of body weight, and had polydipsia and polyuria. Horses 2, 3, and 4 developed persistent hyperphosphatemia. Horse 2 remained normocalcemic whereas horses 3 and 4 became hypercalcemic by day 28. In horse 3, serum vitamin D2 metabolite concentrations on days 0, 1, 14, and 26 were: vitamin D2 (ng/ml) = less than 5.0, 5.7, 71.4, and 188.0; 25-hydroxy-vitamin D2 (ng/ml) = less than 5.0, less than 5.0, 43.1, and 117.5; and 1,25-dihydroxy-vitamin D (pg/ml) = 19.7, 23.2, 25.0, and 45.7, respectively. In horse 4, serum vitamin D3 metabolite concentrations on the same days were: vitamin D3 (ng/ml) = less than 5.0, 110.0, 1,049.0, and 887.0; 25-hydroxy-vitamin D3 (ng/ml) = less than 5.0, 18.9, 201.0 and 182.0; and 1,25-dihydroxy-vitamin D (pg/ml) = 21.5, 18.9, 25.2, and 21.6, respectively. Urine of horses 2 and 4 became acidic (pH 6). Horses 2, 3, and 4 became hyposthenuric, but the decrease in urine specific gravity (sp gr) in horse 3 occurred only after 3 weeks of treatment and was only moderate (sp gr, 1.018 to 1.021) and nonprogressive. Hyposthenuria was evident in horse 4 on day 4 (sp gr, 1.028), and was progressive and marked (sp gr, days 28 to 32: 1.006 to 1.009). Urine sp gr of horse 2 ranged from 1.002 to 1.007. Fractures were demonstrated radiographically and histologically in the costochondral junctions of horses 3 and 4. Mineralization of cardiovascular and other soft tissues developed in horses 3 and 4, with lesions being more severe and having a wider tissue distribution in horse 4.

Toxicity and dose-response studies of 1 alpha-hydroxyvitamin D2 in LH beta-Tag transgenic mice.

PURPOSE: The study objective is to determine the effectiveness of a vitamin D analogue, 1 alpha-hydroxyvitamin D2 (1 alpha-OH-D2), in inhibiting retinoblastoma in a transgenic retinoblastoma model (LH beta-Tag mouse) and to evaluate its toxicity. Previous studies of 1 alpha-OH-D2 in athymic mice with human retinoblastoma xenografts suggested efficacy in tumor suppression and suitability for human treatment. METHODS: LH beta-Tag mice (N = 142), 8 to 10 weeks old, were randomly assigned to treatment groups receiving either control (vehicle) or 0.1, 0.3, 0.5, or 1.0 microgram/day of 1 alpha-OH-D2 via oral gavage five times a week for 5 weeks. Animals were then euthanized. The eyes were enucleated, processed histologically, and serially sectioned. Three sections of each eye were microscopically examined, and mean tumor area was measured using Optimus software. Toxicity was assessed by mortality, weight loss, serum calcium levels, and kidney calcification. RESULTS: The mean tumor size in each 1 alpha-OH-D2 group was smaller than in controls (P values < .02): control, 90,248 microns 2; 0.1 microgram, 31,545 microns 2; 0.3 microgram, 16,750 microns 2; 0.5 microgram, 30,245 microns 2; and 1.0 microgram, 16,049 microns 2. No dose-dependent response curve was evident. Mortality was higher in the groups receiving the 0.5 microgram and 1.0 microgram doses (P values < .01) than in the other treatment groups and the control group. CONCLUSION: In the LH beta-Tag mouse, 1 alpha-OH-D2 inhibits retinoblastoma with no increased mortality at lower doses (0.1 to 0.3 microgram). 1 alpha-OH-D2 has been approved by the Food and Drug Administration as an investigative drug for cancer treatment and has shown efficacy with low levels of toxicity in adult cancer trials. 1 alpha-OH-D2 meets the criteria for human clinical trials.

New model of atherosclerosis in sand rats subjected to a high cholesterol diet and vitamin D2.

In order to defeat the atheroresistance in sand rats, 25 animals were given a high cholesterol diet for 45 days, which was then associated with oral treatment with vitamin D2 2000 IU/day for a further 45 days. At days 0, 45 and 90, plasma parameters, and aortic and heart morphology were examined. Results showed at D45 hypercholesterolaemia, increased plasma LDL and VLDL cholesterol, oxidized LDL, triglycerides, free fatty acids (FFA) and calcium levels and moderate hyperinsulinaemia. At D90, plasma-oxidized LDL and FFA were more enhanced, whereas calcium level was reduced. Development of hyperglycaemia was associated with hyperinsulinaemia and insulin resistance. The vitamin D2 administration induced advanced lesions, represented by the degenerescence of elastic lamina, smooth muscle cell proliferation and lipid calcic plaque at an ulcerated stage in most cases. The ischaemic effects were represented by acute myocardial infarction. The potential of the sand rat to develop atherosclerotic lesions at different stages opens the field to therapeutic tests of new anti-atherogenic agents.

[Activity of elastase and its inhibitors in arterial tissues and blood serum under experimental arterio-atherosclerosis]. / Aktyvnist' elastazy ta ïï inhibitoriv u tkanynakh arterii ta syrovatsi krovi za umov eksperymental'noho arterio-ateroskelrozu.

The role of the elastolytic system serum and arterial tissues in pathogenesis of vascular pathology was investigated on rabbits in experimental arterio-atherosclerosis. Activation of proteolytic enzymes, in particular elastase, sharp alteration capacity of inhibitors in arterial wall both at Menckeberg arteriosclerosis and atherosclerosis, permits to assume, that in the basis these different pathologic processes can lie general mechanisms, which will be realized through disturbance of the elastolytic system balance in blood vessels.

[Comparative study of the hemolytic action of group D vitamins]. / Sravnitel'noe izuchenie gemoliticheskogo distviia vitaminov gruppy D.

Hemolytic effects of the vitamins of the D group (ergocalciferol - D2, cholecalciferol - D3, and 1 alpha-hydroxycholecalciferol - 1 alpha-OH-D3) were compared using rat erythrocytes. The latent period of hemolysis, caused by 1 alpha-OH-D3 was approximately 3-fold shorter as compared with the hemolysis caused by D2 or D3. Apparent values for energy of activation of hemolysis, estimated at 30-45 degrees, constituted for D2 - 23.2 kcal/mol, D3 - 25.3 kcal/mol, 1 alpha-OH-D3 - 13.1 kcal/mol. Despite the higher hemolytic activity, the rate of 1 alpha-ON-D3 autooxidation was distinctly lower than that of D3.

[Comparative study of the biological activity and toxic effect of 1alpha-hydroxycholecalciferol and ergocalciferol in rats]. / Sravnitel'noe izuchenie biologicheskoi aktivnosti i toksicheskogo deistviia 1alpha-oksikholekal'tsiferola i érgokal'tsiferola na krysakh.

Single administration of 0.25 microgram of sunthetic Ialpha-hydroxycholecalciferol (IalphaOHD3) into nephrectomized rats, maintained at D-avitaminous diet, improved the active transport of calcium ions against the concentration gradient in small intestine of these animals, whereas ergocalciferol was biologically inactive under the same conditions. Administration of IalphaOHD3 during 5 days at a dose 0.025 microgram normalized calcium content in blood serum of rats with D-avitaminosis, Increased doses of IalphaOHD3, administered into intact animals, caused transient hyperphosphatemia, hypercalcemia, calcinosis of internal tissues (kidney heart, aorta) as well as death of some animals. IalphaOHD3 exceeded 400-fold the hypercalcemic and calcinose effects of ergocalciferol. LD50 for IalphaOHD3 was equal to 100 microgram/kg, if it was administered during 5 days per os. Tissue calcinosis was developed after administration of a daily dose 10 microgram/kg, moderate hypercalcemia was caused by a daily dose 1 microgram/kg or 0.25 microgram per an animal; this amount is only 10-fold higher as compared with the physiologic requirement. Ergocalciferol caused hypercalcemia and metastatic calcification only at a dose 4000 microgram/kg. Clinical use of IalphaOHD3 at doses, exceeding the physiologic requirements, has to be prohibited due to high activity of the preparation and to toxicity of its increased doses.

[Toxic action of ergocalciferol in strontium rickets]. / Toksicheskoe deistvie érgokal'tsiferola pri strontsievom rakhite.

Tests conducted on albino rats of the Wistar line demonstrated that introduction of large doses of ergocalciferol (vitamin D2) to animals kept on a strontium-rich diet exhibiting signs of rickets brings about the development in them of specific manifestations of the D-vitamin activity, viz. rising level of calcium, strontium and inorganic phosphorus in the blood serum, lowering of the alkaline phosphatase activity and a greater degree of the soft tissues calcification.

Vitamin D2-enriched button mushroom (Agaricus bisporus) improves memory in both wild type and APPswe/PS1dE9 transgenic mice.

Vitamin D deficiency is widespread, affecting over 30% of adult Australians, and increasing up to 80% for at-risk groups including the elderly (age>65). The role for Vitamin D in development of the central nervous system is supported by the association between Vitamin D deficiency and incidence of neurological and psychiatric disorders including Alzheimer's disease (AD). A reported positive relationship between Vitamin D status and cognitive performance suggests that restoring Vitamin D status might provide a cognitive benefit to those with Vitamin D deficiency. Mushrooms are a rich source of ergosterol, which can be converted to Vitamin D2 by treatment with UV light, presenting a new and convenient dietary source of Vitamin D2. We hypothesised that Vitamin D2-enriched mushrooms (VDM) could prevent the cognitive and pathological abnormalities associated with dementia. Two month old wild type (B6C3) and AD transgenic (APPSwe/PS1dE9) mice were fed a diet either deficient in Vitamin D2 or a diet which was supplemented with VDM, containing 1±0.2 µg/kg (∼54 IU/kg) vitamin D2, for 7 months. Effects of the dietary intervention on memory were assessed pre- and post-feeding. Brain sections were evaluated for amyloid ß (Aß) plaque loads and inflammation biomarkers using immuno-histochemical methods. Plasma vitamin D metabolites, Aß40, Aß42, calcium, protein and cholesterol were measured using biochemical assays. Compared with mice on the control diet, VDM-fed wild type and AD transgenic mice displayed improved learning and memory, had significantly reduced amyloid plaque load and glial fibrillary acidic protein, and elevated interleukin-10 in the brain. The results suggest that VDM might provide a dietary source of Vitamin D2 and other bioactives for preventing memory-impairment in dementia. This study supports the need for a randomised clinical trial to determine whether or not VDM consumption can benefit cognitive performance in the wider population.