Normalization of serum calcium restores fertility in vitamin D-deficient male rats.

We performed experiments to determine whether treatment with vitamin D or 1,25-dihydroxycholecalciferol could reverse male infertility caused by vitamin D deficiency. Additionally, an attempt was made to distinguish between a direct and an indirect effect of 1,25-dihydroxycholecalciferol on reproductive tissue. Vitamin D-deficient male rats with impaired fertility were treated with vitamin D and 1,25-dihydroxycholecalciferol for 3 wk, then mated. Secondly, vitamin D-deficient male rats were made normocalcemic by increasing dietary calcium, and their fertility was compared with that of vitamin D-deficient, hypocalcemic rats. The fertility of male rats was restored by treatment with either vitamin D or 1,25-dihydroxycholecalciferol. However, fertility was also restored in vitamin D-deficient animals by feeding them a diet supplemented with high levels of calcium. These results indicate that the influence of vitamin D and its active metabolite, 1,25-dihydroxycholecalciferol, on male fertility is indirect. Vitamin D and 1,25-dihydroxycholecalciferol seemed to influence male fertility by acting on classic target tissues and regulating levels of calcium in reproductive tissues.     

Vitamin D status in the elderly: seasonal substrate deficiency causes 1,25-dihydroxycholecalciferol deficiency

The seasonal variation of 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol was analyzed in 240 elderly subjects (mean age: 78 yr) in Belgium. Serum 25-hydroxycholecalciferol was lowest from February until May (mean levels less than 25 nmol/L). Summer peak levels were, however, not higher than nadir levels in younger control subjects. A seasonal variation in total and free 1,25-dihydroxycholecalciferol concentrations was also observed in the geriatric population with a nadir in February and March (50 +/- 24 pmol/L). The peak values in summer (110 +/- 33 pmol/L) were not different from those of the younger controls. Serum calcium and phosphate were decreased whereas alkaline phosphatase and parathyroid hormone were increased throughout the year in the geriatric patients. Oral 25-hydroxycholecalciferol treatment rapidly normalized serum 1,25-dihydroxycholecalciferol concentrations in vitamin D-deficient subjects. Deficiency of both the vitamin D substrate and hormone is frequent in the elderly population in Belgium.     

Effect of lead ingestion on functions of vitamin D and its metabolites

A study of the effect of ingestion of lead on the metabolism and function of vitamin D was carried out in rats fed diets varying in calcium and phosphorus content. The ingestion of 0.82% lead as lead acetate suppressed plasma levels of 1,25-dihydroxycholecalciferol in rats fed either a low phosphorus or a low calcium diet while it had no effect on this parameter in rats fet either a high calcium diet or a normal phosphorus diet. Most important, the ingestion of lead totally blocked the intestinal calcium transport response to cholecalciferol, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol. On the other hand, the ingestion of lead acetate had no influence on the mobilization of calcium from bone, the elevation of serum inorganic phosphorus and in the mineralization of rachitic bone in the same animals. Thus by the feeding of 0.82% lead on the intestinal responses to vitamin D and its metabolites was greatest in animals fed a low calcium or a low phosphorus diet, it was present with all diets tested.     

Phosphate transport by plasma membranes of enterocytes during development: role of 1,25-dihydroxycholecalciferol.

The present studies were designed to investigate phosphate transport across the brush border and basolateral membranes of enterocytes and to determine the effect of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on these processes in suckling and adolescent rats. Vitamin D deficiency was induced in suckling rats by feeding pregnant dams a vitamin D-deficient diet 48 h after insemination; they were then kept in the dark. Vitamin D deficiency in the adolescent rats was induced by feeding the vitamin D-deficient diet to weanling rats for 4 wk. V max values for Na(+)-dependent phosphate uptake in the brush border membranes of vitamin D-deficient and 1,25(OH)2D3-injected suckling rats was 0.7 +/- 0.1 and 1.5 +/- 0.2 nmol.mg protein-1.10 s-1 (P less than 0.01), respectively; V max values in adolescent rats were 0.2 +/- 0.05 and 0.36 +/- 0.04 nmol.mg protein-1.10 s-1 (P less than 0.05), respectively. Vmax values for Na(+)-dependent phosphate uptake in basolateral membranes of vitamin D-deficient and 1,25(OH)2D3-treated suckling rats were 0.006 +/- 0.001 and 0.047 +/- 0.006 nmol.mg protein-1.10 s-1 (P less than 0.01).     

Biological activity of 1 alpha,25-dihydroxyergocalciferol in rachitic chicks and in rats

The bioactivity of chemically synthesized 1 alpha,25-dihydroxyergocalciferol (1,25(OH)2D2) was investigated in rachitic chicks and in vitamin D-deficient rats. In prophylactic and in curative chick assays 1,25(OH)2D2 is about 10 times less active than 1 alpha,25-dihydroxycholecalciferol (1,25(OH)2D3). Since in the same bioassay vitamin D2 is more than 80 times less active than vitamin D3, discrimination against vitamin D2 in chickens must occur at two points, before and after the formation of 1,25(OH)2D2. Receptor binding studies revealed that the chick duodenal receptor binds 1,25(OH)2D2 with the same capacity as 1,25(OH)2D3. In rats 1,25(OH)2D2 proved to have the same antirachitic activity as 1,25(OH)2D3 and might become of therapeutic interest for application in man and domestic animals if the expectations of lower toxicity are confirmed.     

Biological activity of 24,24-difluoro-25-hydroxycholecalciferol in chicks

The biological activity of subcutaneously injected 24,24-difluoro-25-hydroxycholecalciferol was compared with that of 25-hydroxycholecalciferol in the vitamin D-deficient growing chick. 24,24-Difluoro-25-hydroxycholecalciferol is equal to 25-hydroxycholecalciferol in the stimulation of: 1) growth, 2) intestinal calcium absorption, 3) elevation of serum calcium and serum phosphorus, 4) healing of rachitic cartilage (radiography), and 5) mineralization of rachitic bone (bone ash). The response appears to be linear in the range of 13.0 to 325 pmol daily. Since 24,24-difluorocholecaliferol cannot be 24-hydroxylated to produce either 24,25-dihydroxycholecalciferol or 1,24,25-trihydroxycholecalciferol, while it can be 1 alpha-hydroxylated to produce 24,24-difluoro-1,25-dihydroxycholecalciferol, these results demonstrate that 24-hydroxylation is not required for the known functions of cholecalciferol in the chick.     

Reproductive defects are corrected in vitamin d-deficient female rats fed a high calcium,phosphorus and lactose diet

Vitamin D-deficient female rats are capable of reproduction; however, vitamin D deficiency reduces their overall reproductive capacity. It was previously suggested that the reduction in reproductive performance is a direct result of a lack of vitamin D rather than an effect of the hypocalcemia or hypophosphatemia that can be associated with vitamin D deficiency. In the present study, rats were fed one of three diets: 1) 0.47% Ca(+2) and 0.3% phosphorus (P(i)) with vitamin D; 2) 0.47% Ca(+2) and 0.3% P(i) without vitamin D; and 3) 20% lactose, 2% Ca(+2) and 1.25% P(i) without vitamin D. Their reproductive capacity was monitored. Vitamin D-deficient rats fed the high calcium, high phosphorus, 20% lactose diet had normal serum calcium (2.2 +/- 0.16 mmol/L), slightly lower phosphorus (1.5 +/- 0.3 mmol/L), and undetectable 25-hydroxyvitamin D(3). The decrease in reproductive capacity, as indicated by the fertility ratio and pup number per litter previously seen in vitamin D-deficient rats was completely corrected when serum calcium and phosphorus levels were normalized relative to vitamin D-replete rats. It appears likely that the diminished reproductive performance attributed to vitamin D deficiency is the result of hypocalcemia and/or hypophosphatemia caused by vitamin D deficiency.     

Ascorbic acid effects on vitamin D hormone metabolism and binding in guinea pigs

Ascorbic acid deficiency in guinea pigs fed a vitamin D-replete diet caused a moderate reduction of Ca level in serum and bone; 25-hydroxy-cholecalciferol or 25-hydroxyergocalciferol (25-OHD) serum concentration tended to decline; renal 25-hydroxycholecalciferol-1-hydroxylase (1-OHase) activity decreased 50%; and 25-hydroxycholecalciferol-24-hydroxylase activity increased 1.6-fold. Chromatin 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] receptor concentration in the intestinal mucosa decreased 20-30%, and the percentage of occupied receptors decreased from 12-15% to 6-8%. Receptor affinity for 1,25-(OH)2D3 did not change (Kd = 0.24-0.26 nmol/L, Kd2 = 0.06-0.10 nmol/L), but the cooperativity coefficient decreased from 1.7 to 1.4. Vitamin C deficiency potentiated effects of vitamin D deprivation and impaired a restorative action of vitamin D. It was accompanied by a marked delay in the elevation of 25-OHD concentration in serum as well as decreased 1-OHase activity in kidneys and a lower concentration of occupied 1,25-(OH)2D3 receptors in the intestinal mucosa. The data demonstrate a critical role for ascorbic acid in vitamin D metabolism and binding.     

Vitamin D deficiency enhances the growth of MC-26 colon cancer xenografts in Balb/c mice

Vitamin D deficiency has been associated with increased risk of colon cancer in epidemiologic and prospective clinical studies. In vitro and in vivo studies demonstrated that 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and its analogs inhibit colon cancer cell proliferation. Few studies have evaluated the effect of vitamin D deficiency on the development and growth of colon cancer. To assess the antiproliferative effects of 25-hydroxyvitamin D [25(OH)D] and 1,25(OH)2D3 in vitro, we cultured MC-26 (a colon cancer cell line) in the presence of 25(OH)D3 and 1,25(OH)2D3 and performed [3H]thymidine incorporation. The proliferation of MC-26 was significantly inhibited by both 25(OH)D3 and 1,25(OH)2D3. To determine the effect of vitamin D deficiency on colon cancer proliferation, Balb/c mice were rendered vitamin D deficient by feeding them a vitamin D-deficient diet for 3 mo. A group of vitamin D-sufficient mice was given the same diet with supplemental vitamin D. The mice were injected with MC-26 colon cancer cells and the tumors were measured daily for 20 d. Vitamin D-sufficient mice had 40% smaller tumors than vitamin D-deficient mice. The tumors were evaluated for mRNA expression of the vitamin D receptor (VDR) and 25-hydroxvitamin D-1alpha-hydroxylase (1alpha-OHase) by quantitative RT-PCR. The expression of the mRNA for the VDR and the 1alpha-OHase was 37- and 6-fold higher, respectively, in the vitamin D-sufficient mice compared with the vitamin D-deficient mice. We conclude that vitamin D deficiency enhances the growth of colon cancer in mice. The tumor expression of VDR and 1alpha-OHase indicates possible autocrine/paracrine cell growth regulation by vitamin D.     

Zinc nutritional status modulates the response of 1,25-dihydroxycholecalciferol to calcium depletion in rats.

Male Lewis rats (n = 27) were fed a nonpurified diet containing 0.9% calcium, 0.7% phosphorus, and 0.005% zinc until 8 wk of age. At this time rats were assigned randomly to one of two groups. Both groups were fed a low calcium, low zinc, purified diet (0.2% calcium, 0.4% phosphorus, less than 0.00007% zinc), but one group was fed 1.78 mg Zn/(animal.d). The zinc-replete animals were individually matched by weight to the zinc-depleted animals and pari-fed. Balances and plasma concentrations of zinc, calcium, and phosphorus and parathyroid hormone, 25 hydroxycholecalciferol [25(OH)D] and 1,25-dihydroxycholecalciferol [1,25(OH)2D] were determined at the start of calcium depletion and 2 wk later. Calcium and 25(OH)D levels were lower in both groups after calcium depletion. Dietary zinc had no significant effect on calcium or 25(OH)D levels. Phosphorus concentrations were lower after calcium depletion, but phosphorus concentration was higher in the zinc-depleted compared with the zinc-replete group at the end of the experiment. 1,25(OH)2D increased in both groups, but was higher in the zinc-replete than the zinc-depleted group at the end of the experiment. Calcium and phosphorus balances were greater in the zinc-depleted group at the end of the experiment. We conclude zinc depletion diminishes the response of 1,25(OH)2D to calcium depletion in rats. The mechanism is unknown, but may involve nonhormonally mediated changes in gastrointestinal absorption of calcium and phosphorus or an affect of zinc on extraintestinal processes.     

Effect of the maternal vitamin D status at parturition on the vitamin D status of the neonatal calf

The plasma concentrations of calcium, phosphorus, magnesium, hydroxyproline, vitamin D, and vitamin D metabolites were determined in cows and their colostrum-deprived calves. At birth, calf plasma calcium, phosphorus, and hydroxyproline concentrations were not correlated (P greater than 0.05) with the maternal plasma concentrations of these substances. There was a high degree of correlation between maternal and neonatal calf plasma concentrations of 25-hydroxyergocalciferol (r = 0.733), 25-dydroxycholecalciferol (r = 0.888), 24,25-dihydroxyergocalciferol (r = 0.770), 24,25-dihydroxycholecalciferol (r = 0.629), and 25,26-dihydroxycholecalciferol (r = 0.840). Neonatal calf plasma concentrations of 1,25-dihydroxyvitamin D were low (41.2 +/- 3.4 pg/ml) and had no correlation with maternal concentrations (r = 0.219, P greater than 0.05). Neonatal plasma calcium and inorganic phosphorus concentrations were correlated (P less than 0.05) with maternal plasma concentrations of 1,25-dihydroxyvitamin D (r = 0.559 and 0.525, respectively). Vitamin D status of the dam, therefore, appears to be important in determining neonatal calf plasma concentrations of 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 25,26-dihydroxyvitamin D, and, in addition, the plasma calcium and inorganic phosphorus status of the neonatal calf is apparently dependent on maternal concentrations of 1,25-dihydroxyvitamin D.     

Moderate cholecalciferol supplementation depresses intestinal calcium absorption in growing dogs

Hormonal regulation of calcium (Ca) absorption was investigated in a cholecalciferol (vitamin D(3))-supplemented group (hVitD) vs. a control group (cVitD) of growing Great Danes (100 vs. 12.5 micro g vitamin D(3)/kg diet). Although Ca intakes did not differ, fractional Ca absorption was significantly lower in the hVitD group than in the cVitD group. There were no differences in plasma concentrations of Ca, inorganic phosphate, parathyroid hormone, growth hormone or insulin-like growth factor I between groups. Plasma 25-hydroxycholecalciferol [25(OH)D(3)] concentrations were maintained in the hVitD dogs at the same levels as in the cVitD dogs due to increased turnover of 25(OH)D(3) into 24,25-dihydroxycholecalciferol [24,25(OH)(2)D(3)] and 1,25-dihydroxycholecalciferol [1,25(OH)(2)D(3)]. In hVitD dogs, the greater plasma 24,25(OH)(2)D(3) concentration and the enhanced metabolic clearance rate (MCR) of 1,25(OH)(2)D(3) indicated upregulated 24-hydroxylase activity. The increased MCR of 1,25(OH)(2)D(3) decreased plasma 1,25(OH)(2)D(3) concentrations. In hVitD dogs, the greater production rate of 1,25(OH)(2)D(3) was consistent with the 12.9-fold greater renal 1alpha-hydroxylase gene expression compared with cVitD dogs and compensated to a certain extent for the accelerated MCR of 1,25(OH)(2)D(3). The moderately decreased plasma 1,25(OH)(2)D(3) concentration can only partially explain the decreased Ca absorption in the hVitD dogs. Intestinal vitamin D receptor concentrations did not differ between groups and did not account for the decreased Ca absorption. We suggest that 24,25(OH)(2)D(3) may downregulate Ca absorption.     

All-trans retinoic acid antagonizes the action of calciferol and its active metabolite, 1,25-dihydroxycholecalciferol, in rats

An antagonistic interaction between retinol and calciferol has been established. However, the mechanism by which this antagonism occurs is unclear. One possibility is that retinol affects the metabolism of calciferol. To investigate this hypothesis, retinol- and calciferol-depleted rats were given various amounts of ergocalciferol, cholecalciferol, 1alpha,25-dihydroxycholecalciferol [1,25(OH)2D3], or 24,24-difluoro-1alpha,25-dihydroxycholecalciferol [24-F2-1,25(OH)2D3] in combination with various amounts of retinyl acetate or all-trans retinoic acid (ATRA) in a series of studies. Rats administered 1720 or 3440 microg retinyl acetate once every 3 d for 33 d in combination with 25.8 ng ergocalciferol or 25 ng cholecalciferol every 3 d had lower serum calcium and greater serum phosphorus concentrations than rats fed 0 or 11.4 mug retinyl acetate every 3 d. In addition, rats fed 400 microg ATRA/d in combination with 25.8 ng ergocalciferol every 3 d, 25 ng cholecalciferol every 3 d, 2-5 ng 1,25(OH)2D3/d, or 0.5-1 ng 24-F2-1,25(OH)2D3/d had significantly lower serum calcium and higher serum phosphorus concentrations than rats not given ATRA in the diet. Therefore, both retinyl acetate and ATRA are able to antagonize the action of ergocalciferol and cholecalciferol in vivo. Additionally, ATRA antagonizes the in vivo action of 1,25(OH)2D3 and an analog, 24-F2-1,25(OH)2D3, that cannot be 24-hydroxylated. Together, these results suggest that retinol does not antagonize the action of calciferol by altering the metabolism of calciferol or 1,25(OH)2D3, but does so by another mechanism.     

Dietary calcium is a major factor in 1,25-dihydroxycholecalciferol suppression of experimental autoimmune encephalomyelitis in mice.

The active form of vitamin D (1,25-dihydroxycholecalciferol) is a potent immune system regulator. Treating mice with 1, 25-dihydroxycholecalciferol and feeding them diets high in calcium can completely suppress the induction of experimental autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE). Experiments described here were carried out on mice in which development of EAE was induced. Mice were fed diets containing various amounts of calcium and 1,25-dihydroxychole-calciferol. Variables measured were as follows: 1) incidence and severity of EAE; 2) serum calcium concentrations; 3) body weight; 4) total number of cells in the lymph nodes; and 5) interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) mRNA levels. When calcium was removed from the diet, the incidence of EAE was reduced 20% in both males and females. Further, the lower the dietary level of calcium, the higher was the dose of 1,25-dihydroxycholecalciferol required to prevent the symptoms. Thus, 1, 25-dihydroxycholecalciferol was found most effective in mice fed a diet adequate or high in calcium. 1,25-Dihydroxycholecalciferol treatment of mice fed high dietary calcium resulted in a decreased number of lymphocytes in the lymph nodes and increased IL-4 and TGF-beta1 mRNA levels. When calcium was omitted from the diet, 1, 25-dihydroxycholecalciferol supplementation increased TGF-beta1 mRNA. Increased IL-4 mRNA and decreased lymphocytes in the lymph nodes in response to 1,25-dihydroxycholecalciferol occurred only when dietary calcium was adequate or high. Our results suggest that dietary calcium and 1,25-dihydroxycholecalciferol are both involved in the prevention of symptomatic EAE.     

Insulin-like growth factor-I stimulates renal 1, 25-dihydroxycholecalciferol synthesis in old rats fed a low calcium diet

The adaptive increase in renal proximal tubule 25-hydroxyvitamin D-alpha-hydroxylase activity (1-OHase) during dietary calcium restriction is mediated by an increase in parathyroid hormone (PTH) and is inhibited by aging. Recent studies in mature (3-4 mo) rats demonstrated that insulin-like growth factor-I (IGF-I) restored stimulation of renal 1,25-dihydroxycholecalciferol [1,25(OH)(2)D(3)] production by low phosphorus diet (LPD), another major stimulus of 1-OHase. These studies were designed to determine whether IGF-I stimulates 1-OHase during low calcium intake in old rats. Male rats were fed a normal calcium diet (NCD, 6 g Ca/kg diet) or low calcium diet (LCD, 0.2 g Ca/kg diet) for 14 d, and recombinant human IGF-I [rhIGF-I, 1.4 mg/(24h 160 kg body wt)] or vehicle was administrated via miniosmotic pump for 72 h before killing. In 4-mo-old male Sprague-Dawley rats, LCD increased in vitro renal 1-OHase activity in the presence but not in the absence of rhIGF-I. LCD increased in vitro1-OHase activity in young (1-mo-old) but not old (24-mo-old) male Fischer 344 rats. RhIGF-I increased 1-OHase activity in 24 mo-old rats fed LCD to levels that were not different from those in 1-mo-old rats fed LCD. The results indicate that the adaptive increase in 1-OHase activity due to a LCD is lost by 4 mo in rats and can be restored by pharmacologic doses of rhIGF-I.     

VITAMIN D AND INSULIN SECRETION

Vitamin D-deficient rats showed impairments in glucose-mediated insulin secretion. These changes are independent of food intake and of serum calcium and phosphorus levels, and can be reversed by vitamin D.     

25-Hydroxyvitamin D 1 alpha- and 24-hydroxylase activities in pig kidney homogenates: effect of vitamin D deficiency

A method was developed for simultaneous assay of 25-hydroxyvitamin D 1 alpha- and 24-hydroxylase in pig kidney homogenates. The products of these enzymes, 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol, were extracted from the in vitro incubation mixtures, isolated and purified by gel filtration and high-performance liquid chromatography, identified by ultraviolet absorption spectrometry, and high performance liquid chromatography with a second solvent system and quantified relative to authentic standards with a 254-nm detector system. Assay conditions included 12.5 microM substrate (25-hydroxycholecalciferol) concentration and an incubation time of 15 minutes at 37 degrees C, which was on the linear portion of time curves for both enzymes. Maximum enzyme velocity was 1548 pmol/minute per gram kidney tissue for 1 alpha-hydroxylase and 286 pmol/minute per gram kidney tissue for 24-hydroxylase. The apparent Km for pig kidney 25-hydroxyvitamin D 1 alpha-hydroxylase (1 alpha-hydroxylase) was 445 nM and for 25-hydroxyvitamin D 24-hydroxylase (24-hydroxylase) was 833 nM. We also demonstrated the use of this assay in pigs fed a semisynthetic diet with or without vitamin D. Pigs fed vitamin D-deficient diet had a 5- to 10-fold increase in 1 alpha-hydroxylase activity, severe hypocalcemia, low plasma, 1,25-dihydroxycholecalciferol, very low plasma (undetectable) 24,25-dihydroxycholecalciferol concentration, and no detectable 24-hydroxylase activity compared to those fed the vitamin D-replete diet.     

Cholecalciferol requirements of young turkeys under normal conditions and during recovery from rickets

Day-old turkeys fed vitamin D-deficient diets became rachitic within 17-24 days. The symptoms included reductions in body weight, plasma calcium and inorganic phosphorus, plasma and intestinal calcium-binding protein (CaBP), plasma 25-hydroxycholecalciferol [25(OH)D3], bone ash, and kidney 25(OH)D3-24-hydroxylase and a rise in kidney 25(OH)D3-1-hydroxylase activity. Supplementation of the diet with 12.5 micrograms cholecalciferol per kilogram was sufficient to promote maximal body weight and normal plasma calcium, Plasma calcium, plasma phosphorus and bone ash. Feeding diets containing 250 or 1250 micrograms cholecalciferol per kilogram resulted in a reduced body weight. An increased in the concentration of plasma 25(OH)D3 with increasing dietary cholecalciferol concentration was observed. Feeding vitamin D-deficient rachitic birds for 4 days a diet containing 50 micrograms cholecalciferol per kilogram restored plasma calcium and phosphorus and bone ash. Body weight remained lower than that of the control for an additional 6-day period. Additional cholecalciferol, 25(OH)D3 or 1 alpha-hydroxycholecalciferol in the diet, intramuscular injection of the vitamin D derivatives, or a high-calcium, high-phosphorus diet did not accelerate the recovery from the rachitic state.     

Effect of sow vitamin D status at parturition on the vitamin D status of neonatal piglets

The plasma concentrations of calcium, phosphorus, vitamin D, and vitamin D metabolites were determined in cholecalciferol-treated sows and untreated sows at parturition and their piglets (at birth and at 10 days of age) to determine the relationship between sow vitamin D status and neonatal piglet vitamin D status. At birth, there was a high degree of correlation between sow and piglet plasma concentrations of 25-hydroxycholecalciferol (r = 0.944), 24,25-dihydroxycholecalciferol (r = 0.895), and 25,26-dihydroxycholecalciferol (r = 0.737). Neonatal piglet plasma 1,25-dihydroxyvitamin D was low (42.0 +/- 10.2 pg/ml) and was not correlated with maternal plasma 1,25-dihydroxyvitamin D (r = 0.022). Neonatal plasma calcium and phosphorus were significantly correlated (P less than 0.05) with maternal plasma 1,25-dihydroxyvitamin D (r = 0.515 and 0.581, respectively). Parenteral cholecalciferol treatment of sows before parturition proved an effective means of supplementing young piglets with cholecalciferol (via the sow's milk) and its more polar metabolites via placental transport. However, it had no significant effect on either the plasma mineral or 1,25-dihydroxyvitamin D status of the sow or young piglet.