1,25-dihydroxyvitamin D3 receptor is upregulated in aortic smooth muscle cells during hypervitaminosis D

Several studies have demonstrated that excess of vitamin D3 is toxic particularly to vascular tissues. A notable pathological feature is arterial calcification. The nature of the toxic metabolite in hypervitaminosis D and the pathogenesis of arterial calcification are not clearly understood. The present study was undertaken to explore whether arterial calcification is a sequel of increased calcium uptake by arterial smooth muscle mediated by up regulation of vitamin D receptor in the cells in response to elevated circulating levels of vitamin D3 in serum. The experimental study was performed in 20 New Zealand white female rabbits aged 6 months. Animals in the test group were injected 10,000 IU of cholecalciferol intramuscularly twice a week for one month. Six control animals were given intra-muscular injections of plain cottonseed oil. Animals were sacrificed and aortas were examined for pathological lesions, 1,25-dihyroxyvitamin D3 (1,25(OH)2 D3) receptor levels and 45Ca uptake in smooth muscle cells. Serum samples collected at intervals were assayed for levels of 25-OH-D3 and calcium. The results showed that in animals given injections of cholecalciferol, serum levels of 25-OH-D3 were elevated. In four of these animals calcification and aneurysmal changes were seen in the aorta. Histological lesions comprised of fragmentation of elastic fibers as well as extensive loss of elastic layers. 1,25(OH)2 D3 receptor levels were up regulated and 45Ca uptake enhanced in aortas of animals which were given excessive vitamin D3. The evidences gathered suggest that excess vitamin D is arteriotoxic and that the vitamin induces arterial calcification through up regulation of 1,25(OH)2D3 receptor and increased calcium uptake in smooth muscle cells of the arteries.     

(Ca2+ + Mg2+)-ATPase activity in plasma membrane of circulating mononuclear cells. Lack of a direct effect of vitamin D

The in vivo effect of vitamin D on (Ca2+ + Mg2+)-ATPase activity was examined in a plasma membrane fraction of rat circulating mononuclear cells (MPM). Although there was no significant difference in the ATPase activities in red blood cell ghosts, (Ca2+ + Mg2+)-ATPase activity in MPM was significantly higher (p less than 0.05) in long-term vitamin D3-replete rats (100 IU/day for 6 months) than that in vitamin D-deplete rats (for 6 months). In rats maintained on vitamin D-deficient diets for 5-7 weeks, in vivo administration of either vitamin D3, 2,000 IU orally, 5 days prior to killing or 1,25-dihydroxyvitamin D3, 2.4 nmol, intraperitoneally, 24 h prior to killing failed to show any significant effect on (Ca2+ + Mg2+)-ATPase activity in MPM. (Ca2+ + Mg2+)-ATPase activity in MPM from rats maintained on vitamin D-deficient diet with high calcium content (1.8%) was significantly higher (p less than 0.05) than that from rats maintained on vitamin D-deficient diet with low calcium content (0.3%). Moreover, in vitro addition of vitamin D3 metabolites did not show any effect on (Ca2+ + Mg2+)-ATPase activity in MPM. These data suggest that decreased (Ca2+ + Mg2+)-ATPase activity in MPM from long-term vitamin D-deplete rats resulted from an adaptation to low extracellular calcium rather than vitamin D depletion.     

Actions of vitamins D2 and D3 and 25-OHD3 in anticonvulsant osteomalacia.

In 54 epileptic outpatients treated for at least one year with anticonvulsants the bone mineral content (B.M.C.), an estimate of total body calcium, and serum calcium were measured before and during treatment with three doses of cholecalciferol (vitamin D3; 200, 100, and 50 mu-g daily) and 25-hydroxycholecalciferol (25-OHD3; 40, 20, and 10 mu-g daily) for 12 weeks. The results, when compared with the effects of calciferol (vitamin D2; 200, 100, and 50 mu-g daily) in 40 epileptic outpatients, showed different actions in anticonvulsant osteomalacia of vitamin D2 on the one hand and vitamin D3 and 25-OHD3 on the other. In the patients who received vitamin D2 an increase in B.M.C. was found whereas serum calcium was unchanged. The patients who received vitamin D3 or 25-OHD3 showed an increase in serum calcium but unchanged values of B.M.C. The results suggest that liver enzyme induction cannot alone explain anticonvulsant osteomalacia.     

Effects of vitamin D3 on the uptake and release of calcium by isolated intestinal mitochondria

Administration of vitamin D3 or 1,25 (OH)2D3 to rachitic chicks produces a decrease of 45Ca uptake by mitochondria from intestinal mucosa. This effect of vitamin D3 shows tissue specificity, since it was not observed in liver mitochondria from the same animals. The Km values were similar (about 10 microM) for intestinal mitochondria from rachitic and treated animals. The Ca2+ efflux in previously loaded mitochondria was not changed by treatment. The Ca content of recently isolated mitochondria was strikingly lower after vitamin D3 administration. It is concluded that vitamin D3 may participate in the mechanism which regulates the intramitochondrial Ca concentration.     

1,25-Dihydroxyvitamin D3-mediated intestinal calcium transport. Biochemical identification of lysosomes containing calcium and calcium-binding protein (calbindin-D28K)

A variety of intestinal cell organelles and proteins have been proposed to mediate 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3)-stimulated calcium absorption. In the present study biochemical analyses were undertaken to determine the subcellular localization of 45Ca after calcium transport in vivo in ligated duodenal loops of vitamin D-deficient chicks injected with 1.3 nmol of 1,25-(OH)2D3 or vehicle 15 h prior to experimentation. Separation of Golgi, mitochondria, basal lateral membrane, and lysosome fractions in the epithelial homogenates was achieved by differential sedimentation followed by centrifugation in Percoll gradients and evaluation of appropriate marker enzyme activities. Both vitamin D-deficient and 1,25-(OH)2D3-treated chicks had the highest levels of 45Ca-specific activity in lysosomal fractions. The lysosomes were also the only organelles to exhibit a 1,25-(OH)2D3-mediated difference in calcium content, increasing to 138% of controls. Lysosomes prepared from 1,25-(OH)2D3-treated chicks also contained the greatest levels of immunoreactive calbindin-D28k (calcium-binding protein). Chloroquine, a drug known to interfere with lysosomal function, was tested and found to inhibit 1,25-(OH)2D3-stimulated intestinal calcium absorption. Neither 1,25-(OH)2D3 nor chloroquine affected [3H]2O transport. In additional experiments, microsomal membranes (105,000 X g pellets) were subjected to gradient centrifugation. The highest levels of 45Ca-specific activity and calcium-binding protein in material from 1,25-(OH)2D3-treated chicks were found in fractions denser than endoplasmic reticulum and may represent endocytic vesicles. In studies on intestinal mucosa of 1,25-(OH)2D3-treated birds fractionated after 30 min of exposure to lumenal Ca2+ or Ca2+ plus chloroquine, 45Ca was found to accumulate in lysosomes and putative endocytic vesicles, relative to controls. A mechanism involving vesicular flow is proposed for 1,25-(OH)2D3-mediated intestinal calcium transport. Endocytic internalization of Ca2+, fusion of the vesicles with lysosomes, and exocytosis at the basal lateral membrane complete the transport process.     

Kinetic studies of calcium movements in intestinal cells: Effects of vitamin D deficiency and treatment

Summary The calcium distribution among three cellular calcium pools was studied by kinetic analyses in intestinal cells isolated from normal, vitamin D-deficient and vitamin D-repleted chicks. Vitamin D deficiency significantly reduces the cellular⁴⁵Ca uptake by reducing the intracellular exchangeable calcium pool. Calcium efflux from the cells varies depending on the onset of the vitamin D deficiency: at four weeks calcium efflux is greater than control but after the fifth week it decreases and remains significantly lower than control. The cytoplasmic calcium pool follows the same biphasic pattern: it is higher at 4 weeks and lower after 5 weeks of D-deficiency. The mitochondrial calcium pool and calcium efflux from this compartment do not show a biphasic pattern. They are markedly depressed from the 4th week of D-deficiency. Eighteen hours after vitamin D administration the cytoplasmic and mitochondrial calcium pools return toward normal; after 42 hours the cytoplasmic pool and calcium efflux from the cell are normal. These data suggest that in D-deficiency, mitochondrial calcium uptake is depressed producing first a rise and then a drop in cytoplasmic calcium. The cytoplasmic calcium is responsible for the changes in cellular calcium efflux. The decreased calcium uptake may be partially due to a decreased cellular exchangeable calcium pool.Presented as a preliminary report at the Fifty-Third Meeting of The Endocrine Society, San Francisco, June, 1971.     

Vitamin D3 metabolites modulate dihydropyridine-sensitive calcium currents in clonal rat osteosarcoma cells

A slowly inactivating inward calcium current was identified in the rat osteosarcoma cell line ROS 17/2.8 using a combination of ion flux and electrophysiological techniques. Voltage dependence, dihydropyridine sensitivity, divalent cation selectivity, and single channel properties identified this current as a high threshold, "L-type" calcium current. Ion flux experiments using 45Ca2+ confirmed that calcium uptake through these channel represents a major pathway for calcium entry into osteosarcoma cells. In resting cells, i.e. at negative membrane potentials, stimulation of both calcium current and rapid 45Ca2+ influx could be elicited by concentrations of 1,25-(OH)2-vitamin D3 between 0.1 and 3 nM. At these concentrations, 1,25-(OH)2-vitamin D3 shifted the threshold for activation of inward calcium current to more negative potentials. At higher concentrations (5-10 nM), inhibitory effects became predominant. These opposing effects are functionally similar to those of the dihydropyridine BAY K 8644. Other vitamin D3 metabolites (25-(OH)-D3 and 24,25-(OH)2-D3) exhibited less potent stimulatory effects and greater inhibition of calcium current than 1,25-(OH)2-D3. These results suggest that (i) vitamin D3 acts as a potent modulator of calcium channel function in osteosarcoma cells, and (ii) intracellular Ca2+-dependent signaling processes may be affected acutely by physiological concentrations of vitamin D3 metabolites.     

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.     

1,25 dihydroxyvitamin D3 enhances the calcium response of keratinocytes

The steroid hormone 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) regulates cell proliferation and differentiation. Intracellular calcium (Cai) concentrations play a crucial role in these events. From our previous studies, we have demonstrated a calcium receptor (CaR) in keratinocytes which appears to regulate the initial release of Cai from intracellular stores in response to extracellular calcium (Cao) and so is likely to participate in the differentiation process. In this study, we determined whether the ability of 1,25(OH)2D3 to enhance Ca++ -induced differentiation was mediated at least in part through changes in the CaR. Keratinocytes were grown in keratinocyte growth medium (KGM) with 0.03 mM, 0.1 mM, or 1.2 mM Ca and treated with 10(-8) M 1,25(OH)2D3 till harvest after 5, 7, 14, and 21 days. CaR mRNA levels were quantitated by polymerase chain reaction. The results were compared to the ability of 1,25(OH)2D3 to enhance calcium-stimulated increases in Cai. In cells grown in 0.03 mM Ca, the CaR mRNA levels decreased with time. 1,25(OH)2D3 stimulated the levels at 5 days and prevented the falloff over the subsequent 16 days. On the other hand, in cells grown in 0.1 or 1.2 mM Ca, the message levels remained high, and 1,25(OH)2D3 had no further effect. To study the functional relationship, we harvested cells after 5 and 7 days in culture following a 24 h treatment with 1,25(OH)2D3 or vehicle to measure the Cai response to 2 mM Cao. The preconfluent cells grown in 0.03 mM Ca showed a nearly twofold increase in the Cai response to Cao when pretreated with 1,25(OH)2D3, whereas the confluent cells and those grown in 1.2 mM Ca showed no enhancement by 1,25(OH)2D3. Studies with 45Ca influx into keratinocytes revealed that 1,25(OH)2D3 enhanced the influx in preconfluent and confluent cells when grown in KGM containing 0.03 mM Ca but not in cells grown in 1.2 mM calcium. We conclude that 1,25(OH)2D3 maintains the CaR mRNA levels in cells grown in 0.03 mM Ca, thus maintaining their responsiveness to Cao and so ensuring their ability to differentiate in response to the calcium signal.     

In vivo and in vitro inhibition of rat liver vitamin D3-25-hydroxylase activity by 19-hydroxy-10(S),19-dihydrovitamin D3

Rats treated with varying amounts of 19-hydroxy-10(S),19-dihydrovitamin D3 prior to administration of physiologic doses of vitamin D3 exhibit normal intestinal calcium transport but are unable to mobilize bone calcium. In contrast, 19-hydroxy-10(R),19-dihydrovitamin D3 had no inhibitory activity. Circulating serum levels of 25-hydroxy[3H]vitamin D3 and 1 alpha, 25-dihydroxy[3H]vitamin D3 are markedly suppressed but not totally eliminated in animals predosed with 19-hydroxy-10(S),19-dihydrovitamin D3 before [3H]vitamin D3. Hepatic 25-hydroxy[3H]vitamin D3 levels were approximately equal in both 19-hydroxy-10(S),19-dihydroviotamin D3 treated and untreated rats. However, the rate of conversion of [3H]vitamin D3 to 25-hydroxyvitamin D3 in vivo is greatly reduced in the treated rats. The inhibitory vitamin analogue was also show to block hepatic microsomal 25-hydroxylation in vitro. These results indicate that 19-hydroxy-10(S),19-dihydrovitamin D3 is a specific inhibitor for a hepatic microsomal vitamin D3-25-hydroxylase system.     

Effect of vitamin D3 administration on serum 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and osteocalcin in vitamin D-deficient elderly people

In elderly institutionalized people, confined to bedroom and receiving no vitamin D supplementation, the frequency of vitamin D deficiency is found very high. Systematic administration of vitamin D has, therefore, been proposed to correct vitamin D deficiency. Within this context, we studied 40 elderly institutionalized subjects (mean age 80.5 + 7.2 yr) with low 25(OH)D3 concentrations (4.4 + 1.8 micrograms/l). Sixteen of them (Group I) had low serum calcium concentrations (less than 2.3 mmol/l) and 24 (Group II) had normal serum calcium concentrations (from 2.3 to 2.6 mmol/l). As hypocalcemia has been shown to regulate 1,25(OH)D3 production independent of PTH in animals and in humans, we compared their respective responses to the administration of vitamin D3. Subjects received a total dose of 15 mg (600,000 IU) of vitamin D3 divided into 3 i.m. injections at one month intervals and were explored before therapy and one and 6 months after the last dose of vitamin D3. The treatment induced a similar marked rise in 25(OH)D3 levels (from 4.1 + 1.7 to 24.4 + 8.7 micrograms/l for group I and from 5.1 + 1.8 to 27.2 + 8.0 micrograms/l for group II) in both groups but increased the 1,25(OH)2D3 concentrations only in group I (from 22.9 + 6.9 to 32.6 + 11.3 ng/l). Meanwhile serum calcium concentrations rose in group I (to low normal range i.e. 2.31 + 0.07 mmol/l) and were unaffected in group II. These results suggest that hypocalcemia is a potent stimulator of renal 1-hydroxylase in elderly people. Furthermore, a transient significant (P less than 0.01) increase in serum osteocalcin (from 10.6 + 4.1 to 14.1 + 5.9 micrograms/l) could be observed in group I which demonstrates for the first time that the osteocalcin response of osteoblasts to stimulation by 1,25(OH)2D3 is retained in very old people.     

Effect of 1,25(OH)2D3 on the relative contributions of skeletal 45Ca and intestinal 40Ca to blood calcium in normal and thyroparathyroidectomized dogs

The effects of gradually increasing doses of 1,25(OH)2D3 on plasma calcium and 45Ca radioactivity were studied in young dogs that had been extensively prelabelled with 45Ca. The effects of orally and intravenously administered 1,25(OH)2D3 were evaluated in normal and thyroparathyroidectomized dogs fed a normal diet. In normal dogs when 1,25(OH)2D3 increased the plasma calcium within the normal range (2.9-3.1 mmol/L) there was no significant increase in plasma 45Ca. In thyroparathyroidectomized dogs, oral or intravenous 1,25(OH)2D3 increased the low blood calcium to a normal level (1.8-2.9 mmol/L) without significantly increasing plasma 45Ca. In normal and thyroparathyroidectomized dogs, any 1,25(OH)2D3-induced increase in plasma calcium above the normal range was associated with a significant increase in 45Ca, indicating mobilization of bone calcium. Intravenous administration of 1,25(OH)2D3 in the normal or thyroparathyroidectomized dogs had a much larger effect than oral doses in mobilizing bone 45Ca when inducing a similar level of hypercalcemia. The major physiological effect of 1,25(OH)2D3 in the low or normal range of plasma calcium is on intestinal absorption of calcium without a significant effect on mobilizing bone calcium. The pharmacological effect of 1,25(OH)2D3 in vivo is to mobilize bone calcium as well as dietary calcium into blood.     

Oral administration of 1,25-dihydroxyvitamin D3 completely protects NOD mice from insulin-dependent diabetes mellitus

1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), the biologically active form of vitamin D, is widely recognized as a modulator of the immune system as well as a regulator of mineral metabolism. The objective of this study was to determine the effects of vitamin D status and treatment with 1,25(OH)(2)D(3) on diabetes onset in non-obese diabetic (NOD) mice, a murine model of human type I diabetes. We have found that vitamin D-deficiency increases the incidence of diabetes in female mice from 46% (n=13) to 88% (n=8) and from 0% (n=10) to 44% (n=9) in male mice as of 200 days of age when compared to vitamin D-sufficient animals. Addition of 50 ng of 1,25(OH)(2)D(3)/day to the diet prevented disease onset as of 200 days and caused a significant rise in serum calcium levels, regardless of gender or vitamin D status. Our results indicate that vitamin D status is a determining factor of disease susceptibility and oral administration of 1,25(OH)(2)D(3) prevents diabetes onset in NOD mice through 200 days of age.     

Regulatory activities of 2 beta-(3-hydroxypropoxy)-1 alpha, 25-dihydroxyvitamin D3, a novel synthetic vitamin D3 derivative, on calcium metabolism

Regulatory activities of 2 beta-(3-hydroxypropoxy)-1 alpha, 25-dihydroxyvitamin D3 [ED-71], a novel synthetic vitamin D3 derivative, on calcium metabolism were investigated. The compound behaved similar to 1 alpha, 25-dihydroxyvitamin D3 [1,25(OH)2D3] in the ex vivo intestinal calcium transport using rat everted gut sac and the in vivo bone mobilization using vitamin D-deficient rats. By means of Raisz's assay method, 45Ca releasing activity of ED-71 was not greater than that of 1,25(OH)2D3. The time course curve of ED-71 in plasma made a mild round shape compared with that of 1,25(OH)2D3 and the former's plasma concentration remained increased longer than the latter's. The therapeutic effect of ED-71 for the animal models with osteoporosis seemed to be better than that of 1,25(OH)2D3. The results suggest that ED-71 may be a promising drug for therapy of osteoporosis.     

Stimulation of 1,25-dihydroxyvitamin D3 production by 1,25-dihydroxyvitamin D3 in the hypocalcaemic rat.

Serum 1,25-dihydroxyvitamin D3 concentration and renal 25-hydroxyvitamin D 1 alpha-hydroxylase activity were measured in rats fed various levels of calcium, phosphorus and vitamin D3. Both calcium deprivation and phosphorus deprivation greatly increased circulating levels of 1,25-dihydroxyvitamin D3. The circulating level of 1,25-dihydroxyvitamin D3 in rats on a low-calcium diet increased with increasing doses of vitamin D3, whereas it did not change in rats on a low-phosphorus diet given increasing doses of vitamin D3. In concert with these results, the 25-hydroxyvitamin D 1 alpha-hydroxylase activity was markedly increased by vitamin D3 administration to rats on a low-calcium diet, whereas the same treatment of rats on a low-phosphorus diet had no effect and actually suppressed the 1 alpha-hydroxylase in rats fed an adequate-calcium/adequate-phosphorus diet. The administration of 1,25-dihydroxyvitamin D3 to vitamin D-deficient rats on a low-calcium diet also increased the renal 25-hydroxy-vitamin D 1 alpha-hydroxylase activity. These results demonstrate that the regulatory action of 1,25-dihydroxyvitamin D3 on the renal 25-hydroxyvitamin D3 1 alpha-hydroxylase is complex and not simply a suppressant of this system.     

Pharmacokinetics of 24,25-dihydroxyvitamin D3 in humans

Pharmacokinetic properties of pharmacological doses of 24,25-dihydroxyvitamin-D3 [24,25(OH)2D3] were determined in healthy volunteers. Four male subjects received 25 micrograms of 24,25(OH)2D3 as an intravenous bolus injection. Plasma concentrations of 24,25(OH)2D3, 25-hydroxyvitamin D and 1,25-dihydroxy-vitamin D were monitored during 14 days. In addition, serum ionized calcium, total calcium, inorganic phosphate, albumin, creatinine and intact hPTH(1-84) were measured during 14 days. The concentration-time curve of 24,25(OH)2D3 could be described by a two-exponential curve with half-lives of 3.0 +/- 0.9 hrs and 8.2 +/- 2.9 days (mean +/- SD). The volume of distribution was 0.19 +/- 0.02 liters/kg. None of the mentioned biochemical parameters, except serum 24,25(OH)2D3, changed markedly. In 18 subjects suffering from primary hyperparathyroidism, taking 25 micrograms of 24,25(OH)2D3 daily during three months, an average plateau level of 39 +/- 12 nmol/l of serum was observed. Bioavailability as estimated from this plateau level was approximately 70%.     

1,25 (OH)2 vitamin D3-induced 45CA uptake in vascular myocytes cultured from spontaneously hypertensive and normotensive rats

The effect of 1,25 (OH)2 vitamin D3 on basal 45Ca uptake was examined in vascular smooth muscle cells cultured from mesenteric arteries of spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) normotensive rats. Basal uptake of 45Ca was significantly greater in myocytes of WKY than SHR at 5, 10, 30 and 60 min incubation with the isotope. Incubation with 1 ng/ml 1,25 (OH)2 vitamin D3 for 48 hr increased basal 45Ca uptake between 1-10 min in SHR and between 5-10 min in WKY. The dose-response relationship indicated that cells from both strains are equally sensitive to the calciotropic effects of 1,25 (OH)2 vitamin D3 with half-maximal stimulation occurring at approximately 0.3-0.4 ng/ml. In cells of both strains maximal stimulation of 45Ca uptake was achieved only after a 12-24 hr period of incubation with hormone and pretreatment with cycloheximide inhibited 1,25 (OH)2 vitamin D3-enhanced 45Ca uptake. Although 45Ca binding by extracellular matrix material was significantly greater in WKY than SHR, 1,25 (OH)2 vitamin D3 had no effect on the amount of matrix 45Ca binding in either strain. These results suggest that 1,25 (OH)2 vitamin D3 induces an increase in intracellular protein synthesis that results in enhanced 45Ca uptake. The similar responses of the two strains indicate that hypertensive smooth muscle is not more sensitive to 1,25 (OH)2 vitamin D3 and the Ca2+ response is a general property of vascular muscle.     

维生素D3对自发性高血压大鼠靶器官炎症的影响

目的探索维生素D3与高血压和炎症的关系。方法自发性高血压大鼠20只,随机分为对照组和实验组,各10只。实验组大鼠腹腔注射维生索D3制剂3μg／kg（溶于20％丙二醇0．5mL中）,每周2次;对照组仅腹腔注射丙二醇0．5mL,两组均干预12周。实验过程中监测大鼠血压变化。干预前后,酶联免疫法检测血清25（OH）D3、钙、白细胞介素-6（IL-6）、基质金属蛋白酶-9（MMP-9）的浓度;计算肾脏-体重比和心脏-体重比;HE染色观察两组大鼠肾脏、心脏、主动脉、小动脉组织病理改变。结果实验组和对照组在干预前血压无差异显著性（P〉0．05）;干预后,实验组和对照组大鼠平均收缩压分别为（157±9）mmHg和（173±8）mmHg（P〈0．05）。实验组的血清25（OH）D3、血钙水平比对照组高（P〈0．05）,IL-6、MMP-9水平实验组比对照组低（P〈0．05）。实验组的心脏-体重比小于对照组（P〈0．05）。实验组的肾脏、心脏和小动脉高血压、炎性损害明显轻于对照组。结论规律的维生素D3用药能够抑制炎症因子IL-6、MMP-9的产生,抑制机体炎症反应,调节控制血压。     

Immunochemical studies on the putative plasmalemmal receptor for 1, 25-dihydroxyvitamin D(3). III. Vitamin D status

The effect of vitamin D status on levels of the putative 1, 25(OH)(2)D(3) membrane receptor (pmVDR) was studied in chick intestine, kidney, and brain. Western analyses and assays for specific [(3)H]1,25(OH)(2)D(3) binding indicated that, in intestine, pmVDR levels were greatest in -D chicks relative to +1,25D and +D animals (P < 0.05). In kidney, protein levels and specific binding followed the order +D > +1,25D, -D. In brain, vitamin D status did not affect protein levels or specific binding levels. In tissue from normal chicks, both protein and specific binding followed the order of intestine > kidney > brain membranes. Intestinal cells were further evaluated for the effect of 1,25(OH)(2)D(3) on selected "rapid responses." Extrusion of (45)Ca in response to 130 pM 1, 25(OH)(2)D(3) in vitro was greater in cells from -D chicks than from +1,25D or normal birds. Analyses of signal transduction events revealed diminished hormone-induced intracellular calcium oscillations (as assessed by fura-2 fluorescence), and lack of steroid-enhanced protein kinase (PK) A activity in intestinal epithelial cells from -D chicks relative to +D chicks. PK C activation by 130 pM 1,25(OH)(2)D(3) was approximately twofold in cells from +D or -D chicks. The combined results indicate that vitamin D status differentially affects the pmVDR in intestine, kidney, and brain. In intestine, vitamin D deficiency differentially affects (45)Ca handling, intracellular calcium oscillations, PK A and PK C activities in response to 1,25(OH)(2)D(3).