Evidence for 1,25-dihydroxyvitamin D3 production by cultured porcine alveolar macrophages

Previous studies have demonstrated that human alveolar and bone marrow macrophages when activated in vitro can metabolize 25-hydroxyvitamin[3H]D3 to 1 alpha,25-dihydroxyvitamin[3H]D3; however, to date no animal models to study this system have been available. In the present study, cultured porcine pulmonary alveolar macrophages from two animals were assayed for their capability for metabolism of 25-hydroxyvitamin[3H]D3. The porcine alveolar macrophages constitutively produced a metabolite of 25-hydroxyvitamin[3H]D3 which was identified as 1 alpha,25-dihydroxyvitamin[3H]D3 by high performance liquid chromatography. The apparent KM was in the range of 300 nM. Unlike human macrophages, treatment of porcine alveolar macrophages with lipopolysaccharide did not stimulate 1 alpha,25-dihydroxyvitamin[3H]D3 production. Addition of 1 alpha,25-dihydroxyvitamin-D3 to macrophages cultures led to a sensitive proportional inhibition of 1 alpha,25-dihydroxyvitamin[3H]D3 synthesis.

Calcium metabolism in early chronic renal failure: implications for the pathogenesis of hyperparathyroidism

Studies in the past showed elevated immunoreactive parathyroid hormone (PTH) serum values in early renal failure, but the assays used in these studies could not discriminate between bioinactive fragments of the PTH peptide and biologically active hormone. The availability of a sensitive PTH assay, which quantitates intact hormone, now allows the analysis of biologically active PTH in renal failure. To characterise more precisely the point of onset of hyperparathyroidism in the course of chronic renal failure and its relation to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], we measured plasma intact PTH and vitamin D metabolite serum values in 63 non-nephrotic uraemic patients (male n = 35, female n = 28, age 31-78 years) with incipient (GFR 60-90 ml/min per 1.73 m3, n = 19) mild (GFR 40-60, n = 22) and moderate (GFR 20-40, n = 22) renal failure, and in 22 age-matched healthy control subjects. Intact PTH concentrations were negatively correlated with GFR (r = -0.57, P less than 0.001). Median plasma intact PTH values (normal range 1.2-6 pmol/l) were 5.6 (range 2.2-13.0) in incipient, 8.1 (2.9-24.0) in mild, and 13.0 (5.4-59.0) in moderate renal failure. Intact PTH values in incipient renal failure were significantly greater than in 22 age-matched control subjects (P less than 0.01). The decline of GFR was paralleled by a progressive decrease in 1,25(OH)2D3 serum values (r = 0.44, P = 0.001). Median values of the hormone (normal range 35-90 pg/ml) were 32 (range 20-66) in incipient (P less than 0.01 vs. age-matched control subjects), 34 (22-74) in mild, and 26 (17-39) in moderate renal failure. In all three groups, mean serum phosphate and total calcium concentrations (corrected for serum protein) were within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of a double antibody radioimmunoassay for quantitation of 1 alpha,25-dihydroxyvitamin D

A sensitive radioimmunoassay (RIA) for 1 alpha,25-dihydroxyvitamin D [1 alpha,25(OH)2-D] with a double antibody (DAB) separation technique to separate free from bound antigen has been developed. The hormone was extracted from 1 ml serum or plasma by Extrelut columns and normal phase high performance liquid chromatography and quantitated in the DAB-RIA. The detection limit of the assay was 3.75 ng/l. The intraassay variation coefficients were 15.9% and 10.5% for samples with 1 alpha,25(OH)2D3 concentrations of 54 ng/l and 130 ng/l, respectively. The interassay variation coefficients were 18.0% and 16.7% for these two concentrations. Mean (and SD) values for 1,25(OH)2D in serum of 40 healthy subjects and 38 patients with chronic renal failure who did not receive 1,25(OH)2D3 were 62.8 ng/ml (22.2) and 12.4 ng/ml (9.8), respectively. The mean value for 7 patients with primary hyperparathyroidism was 66.5 ng/ml (35.8) before surgery. These results compared well with those of an established charcoal-based RIA. Compared to charcoal-based RIAs, the DAB-RIA is faster and requires less laborious assay procedures.

Lymphocyte cell lines from vitamin D-dependent rickets type II show functional defects in the 1 alpha,25-dihydroxyvitamin D3 receptor

Lymphocyte cell lines were established from five patients with vitamin D-dependent rickets, type II (VDDR-II). These lines were established by infection with human T-lymphotrophic virus type I (HTLV-I). Binding of [3H]1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) to its receptor in these cell lines was compared to binding studies using a T-lymphocyte cell line (S-LB1) from a normal individual. The 1,25(OH)2D3 receptor of S-LB1 was comparable to the well-characterized chick intestinal 1,25(OH)2D3 receptor in terms of its ligand binding affinity and capacity, its mobility on 5-20% sucrose gradients, and its adsorption to and elution properties from DNA-cellulose. Three cell lines established from patients with VDDR-II (Rh-VDR, Sh-VDR, and Ab-VDR) showed no specific binding of 1,25(OH)2D3 to a receptor and treatment of the cultured cells with 1,25(OH)2D3 did not stimulate production of 24,25-dihydroxy-vitamin D3 (24,25(OH)2D3), a response which is diagnostic of the presence of a functional 1,25(OH)2D3 receptor. In a fourth cell line, A1-VDR, the receptor for 1,25(OH)2D3 had a low binding capacity and 25(OH)D3-24-hydroxylase activity was not detectable. Induction of 24,25-(OH)2D3 synthesis by 1,25(OH)2D3 was observed in the fifth cell line, designated Ro-VDR, although the sensitivity to hormone treatment was lower than in the control cell line from a normal donor. The capacity of the receptor for 1,25(OH)2D3 was low in Ro-VDR. In all cell lines where 1,25(OH)2D3 binding to a receptor was detectable, the receptor had the typical sedimentation coefficient of 3.7 S on sucrose density gradient analysis. Binding and elution properties to DNA-cellulose, however, differed from normal in both Ro-VDR and A1-VDR cells where elution from DNA-cellulose occurred at a lower salt concentration than is typical of the 1,25(OH)2D3 receptor. While Ro-VDR cells showed typical nuclear localization of the unoccupied 1,25(OH)2D3 receptor, neither the unoccupied nor the occupied receptor from A1-VDR cells was completely localized in the nucleus. In a series of functional studies we found that modulation of the level of the mRNAs coding for both the c-myc oncogene and the growth factor known as granulocyte-monocyte colony stimulating activity by 1,25(OH)2D3 correlated with the 1,25(OH)2D3 receptor status of these cells. Use of these cell lines will facilitate further study of the molecular defect(s) in the receptor for 1,25(OH)2D3 in vitamin D-dependent rickets type II and will allow a correlation with impairment of cellular functions.

1,25-Dihydroxyvitamin D3 inhibits myelopoiesis but not B-lymphopoiesis in long-term bone marrow cultures

The biologically active vitamin D3 metabolite 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) has been demonstrated to have differentiative and antiproliferative effects on myeloid tumors of human or murine origin. Its effects on normal murine hemopoiesis were tested by addition of the seco-steroid to long-term bone marrow cultures optimized for either myelopoiesis or B-lymphopoiesis. The addition of 10(-8) M 1,25(OH)2D3, but not 10(-8) M 25(OH)D3, to myeloid bone marrow cultures (MBMC) resulted in a complete cessation of hemopoiesis by 4 weeks, because no hemopoietic cells or colony-forming units were detected. This result was observed whether or not the cultures were initiated and maintained in hydrocortisone. A potential effect of 1,25(OH)2D3 on the production of myeloid growth factors by adherent layer cells in the cultures was examined, but this function was not affected by 1,25(OH)2D3 treatment. Further, adherent layers that had been treated with 1,25(OH)2D3 for 3 weeks were capable of supporting myelopoiesis upon seeding with a stromal cell-depleted population of bone marrow cells. Transfer of MBMC to lymphoid bone marrow culture (LBMC) conditions results in the cessation of myelopoiesis and the initiation of B-cell production. Lymphopoiesis did not initiate in 1,25(OH)2D3-pretreated MBMC that were transferred to LBMC conditions, indicating that the pool of B-cell precursors present in MBMC had been depleted by exposure of MBMC to 1,25(OH)2D3. When 1,25(OH)2D3 (10(-8) M) was added to MBMC at the time of transfer to LBMC conditions, the seco-steroid did not affect induction of B-lymphopoiesis, although the overall cellularity was less in 1,25(OH)2D3-treated cultures than in control cultures.

Systemic effects of vitamin D

Traditionally perceived as a seco-steroid hormone involved in the regulation of calcium metabolism, 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] is now known also to be active in tissues not directly contributing to mineral metabolism. New data show that 1 alpha,25(OH)2D3 is produced by and interacts with hematopoietic cells. The hormone promotes myeloid differentiation and modulates the function of activated lymphocytes. Another new target tissue for 1 alpha,25(OH)2D3 is the skin, where 1 alpha,25(OH)2D3 enhances differentiation of epidermal cells. Therapeutic application of 1 alpha,25(OH)2D3 or suitable analogues in differentiation disorders of hematopoietic and skin cells is currently under investigation.

[New aspects of endocrine regulation of calcium metabolism]

The maintenance of circulating calcium levels within the narrow physiological range requires the action of two hormones, the polypeptide hormone parathyroid hormone and the steroid hormone 1-alpha-25-dihydroxyvitamin D3. These two hormones act on bone, kidney and intestine to regulate calcium homeostasis. Disorders of mineral metabolism are frequently associated with abnormal regulation of the metabolism of parathyroid hormone or 1-alpha-25-dihydroxyvitamin.

Differential effects of 1,25-dihydroxyvitamin D3 upon intestinal vitamin D3-dependent calbindin (a 28,000-dalton calcium binding protein) and its mRNA in D-replete and D-deficient chickens

The effect of vitamin D3 status upon the responsiveness of chick intestinal epithelium to exogenous 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was studied. Intestinal calbindin [A recent consensus decision was made to redesignate the vitamin D-dependent calcium binding protein as "calbindin-D28K" (R.H. Wasserman (1985) in Vitamin D: Chemical, Biochemical, and Clinical Update (Norman, A.W., Schaefer, K., Grigoleit, H.-G., and Herrath, D.V., Eds.), pp. 321-322, de Gruyter, Berlin/New York).] protein and intestinal calbindin mRNA were quantitated in birds which had been raised on a vitamin D3-deplete (-D) or on a vitamin D3-replete (+D) diet. 1,25(OH)2D3 stimulated intestinal calbindin mRNA levels in -D chickens in a proportional dose-dependent manner, when measured at both 12 and 48 h after administration of the hormone. A first increase was observed with 1,25(OH)2D3 concentrations between 0.065 and 0.65 nmol. The maximal stimulation achieved by 1,25(OH)2D3 (6.5-18 nmol) in -D tissue was approximately 10-fold over the calbindin mRNA levels present in vehicle-treated birds. The increase of calbindin mRNA in -D birds was associated with a similar dose-dependent increase in calbindin protein in 1,25(OH)2D3-treated -D birds after 12 or 48 h. In +D intestine, while exogenous 1,25(OH)2D3 also increased calbindin mRNA levels in a dose-dependent fashion, the maximal stimulation observed after 5 h (1.2- to 2-fold) was clearly less than that observed in -D intestine. In contrast to -D birds, intestinal calbindin levels in +D birds were decreased by administration of exogenous 1,25(OH)2D3. Administration of 32.5 to 65 nmol 1,25(OH)2D3 resulted in an approximately 1.8-fold repression compared to vehicle-treated birds. This differential responsiveness between +D and -D intestines with respect to 1,25(OH)2D3 was not explained either by differences in the uptake in the chromatin fractions of these tissues or by metabolism of radiolabeled 1,25(OH)2D3. Dietary withdrawal of vitamin D3 led to a gradual decline in ambient intestinal calbindin levels, while intestinal sensitivity to 1,25(OH)2D3 was restored. These findings suggest that vitamin D3 status regulates intestinal responsiveness to the seco-steroid 1,25(OH)2D3.

Metabolism of the vitamin D3 derivative (24R)-hydroxycalcidiol by human promyelocytic leukemia cells (HL-60). Isolation and identification of (5Z) and (5E)-(24R)-19-nor-10-oxo-24-hydroxycalcidiol

Human promyelocytic leukemia cells (HL-60 cells) incubated with (24R)-hydroxy[26,27-methyl-3H]calcidiol (0.2 microCi) or non-radioactive (24R)-hydroxycalcidiol (370 micrograms) produced significant quantities of two new vitamin D3 (calciol) metabolites. The metabolites were isolated from HL-60 cell culture media by methanol/chloroform extraction and a series of chromatographic procedures. The two new metabolites were identified as (5Z)- and (5E)-(24R)-19-nor-10-oxo-24-hydroxycalcidiol by HPLC analysis, ultraviolet absorption spectrophotometry, mass spectrometry and Fourier-transform infrared spectrophotometry. According to the isolation and purification procedures, the total amounts of 3.04 micrograms (5Z)-(24R)-19-nor-10-oxo-24-hydroxycalcidiol (lambda max = 310 nm, epsilon = 17070 M-1 cm-1) and 8.89 micrograms (5E)-(24R)-19-nor-10-oxo-24-hydroxycalcidiol (lambda max = 312 nm, e = 24,500 M-1 cm-1) were calculated, assuming an Mr of 418. The activity of 19-nor-10-oxo-(24R)-hydroxycalcidiol to promote HL-60 cell differentiation was higher than the activity of the precursor (24R)-hydroxycalcidiol suggesting a possible biological action of this metabolite in HL-60 cells.

Regulation of 1,25-dihydroxyvitamin D3 production by cultured alveolar macrophages from normal human donors and from patients with pulmonary sarcoidosis

Regulation of the production of the biologically active vitamin D3 sterol 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] by cultured pulmonary alveolar macrophages (PAM) obtained from 6 patients with pulmonary sarcoidosis and from 9 normal subjects was studied. The sarcoid cells, all collected from patients with normal calcium metabolism, synthesized 1,25-(OH)2-[3H]D3 from the substrate 25-hydroxyvitamin [3H]D3 (25OH-[3H]D3), whereas in vitro incubation with recombinant human interferon-gamma (IFN gamma) or lipopolysaccharide (LPS) was required for induction of synthesis of the hormone by normal PAM. Exogenous 1,25-(OH)2D3 (10-100 nmol/L) decreased endogenous hormone production by normal PAM by approximately 45%. The relative inhibitory effect of 1,25-(OH)2D3 was less pronounced in sarcoid PAM, in which 10-100 nmol/L 1,25-(OH)2D3 inhibited 250HD3-1-hydroxylase by approximately 25%. An accompanying induction of the 250HD3-24-hydroxylase, which is typical for renal cells, was found at low levels in only 3 of 10 experiments; in this regard, no differences between sarcoid and normal PAM were apparent. PTH or forskolin did not influence 250HD3 metabolism by PAM. 1,25-(OH)2D3 production by sarcoid PAM was enhanced by lipopolysaccharide and IFN gamma. Likewise, recombinant human interleukin-2 stimulated 1,25-(OH)2D3 production by sarcoid PAM, suggesting a possible role for both IFN gamma and interleukin-2 in the induction of 1,25-(OH)2D3 synthesis by sarcoid PAM in vivo. Recombinant human IFN alpha, IFN beta, and granulocyte-macrophage colony-stimulating factor had little effect. Dexamethasone and chloroquine, which have in vivo antihypercalcemic activity in sarcoidosis, both inhibited 1,25-(OH)2D3 synthesis by sarcoid PAM; chloroquine simultaneously stimulated the 24-hydroxylase. Our studies suggest that the 250HD3-metabolizing system in PAM is in some respects different from renal metabolism of 250HD3.

25-Hydroxyvitamin D3 metabolism by human T-lymphotropic virus-transformed lymphocytes

Production of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] by human T-lymphotropic virus-I (HTLV-I)-infected lymphocytes may be the cause of the hypercalcemia frequently found in HTLV-I-associated adult T-cell lymphoma/leukemia. We examined three HTLV-I-transformed lymphocyte cell lines, two HTLV-II-transformed lymphocyte cell lines, and six HTLV-negative B and T-lymphocyte leukemia cell lines for metabolism of 25-hydroxyvitamin D3 (25OHD3). One HTLV-I-positive cell line, designated S-LB1, converted the substrate 25OH-[3H]D3 to several more polar metabolites, which were identified by high performance liquid chromatographic analysis as putative 1,25-(OH)2D3, 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3], and 1,24,25-trihydroxyvitamin D3 [1,24,25-(OH)3D3]. The other cell lines gave no evidence of 25OH-[3H]D3 metabolism. Likewise, phytohemagglutinin-stimulated normal human lymphocytes did not metabolize 25OH-[3H]D3. The characteristics of 25OHD3 metabolism by S-LB1 cells were investigated in more detail. Kinetic studies revealed average Km values of 92 and 383 nM for 25OHD3 1-hydroxylase and 24-hydroxylase, respectively. Time-course studies showed that both 1,25-(OH)2-[3H]D3 and 24,25-(OH)2-[3H]D3 were further metabolized by S-LB1 cells to more polar compounds [primarily 1,24,25-(OH)3D3] and to compounds from which part of the side-chain had been cleaved. Exogenous 1,25-(OH)2D3 (1) inhibited endogenous 1,25-(OH)2D3 production, (2) stimulated 24,25-(OH)2D3 production, and (3) stimulated production of compounds more polar than 1,25-(OH)2D3. Bovine PTH-(1-34) had no effect on 25OH-[3H]D3 metabolism by S-LB1 cells. Our results indicate that the 25OH-[3H]D3-metabolizing system of cultured HTLV-I-transformed S-LB1 lymphocytes is similar but not identical to that of kidney cell culture systems. It appears, however, that infection of lymphocytes with HTLV does not uniformly result in acquisition of the competence to metabolize 25OHD3.

Synthesis in vitro of 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 by interferon-gamma-stimulated normal human bone marrow and alveolar macrophages

Cultured human macrophages from normal donors were examined for their capability to metabolize 25-hydroxyvitamin D3 (25-(OH)D3). Upon exposure to recombinant human interferon-gamma (IFN-gamma) both bone marrow-derived macrophages (BMM) and pulmonary alveolar macrophages (PAM) produced a polar 25-(OH)D3 metabolite which was purified from conditioned media and unequivocally identified as 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) by UV-absorbance spectrophotometry and mass spectrometry. The BMM and PAM also synthesized a second 25-(OH)D3 metabolite which was structurally identified as 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3). The time course of 25-(OH)D3 metabolism by macrophages suggested that the production of 24,25-(OH)2D3 was stimulated by high intracellular levels of 1,25-(OH)2D3 and not by IFN-gamma. The 1,25-(OH)2D3 obtained from BMM and PAM promoted macrophage-like differentiation of promyelocytic HL-60 leukemia cells and inhibited IFN-gamma production by normal human lymphocytes. Our data suggest that locally high levels of 1,25-(OH)2D3 in the microenvironment of IFN-gamma-stimulated BMM and PAM may modulate the function of hormone-responsive cells.

Granulocyte-macrophage colony-stimulating factor. Sensitive and receptor-mediated regulation by 1,25-dihydroxyvitamin D3 in normal human peripheral blood lymphocytes

We show that 1,25-dihydroxyvitamin D3 (1,25[OH]2D3), the most hormonally active metabolite of vitamin D3, modulates sensitively and specifically both the protein and messenger RNA accumulation of the multilineage growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). The regulation of GM-CSF expression is seen in both normal human mitogen-activated T lymphocytes and T lymphocytes from a line (S-LB1) transformed with human T cell lymphotropic virus 1 (HTLV-1). In contrast, cells from a HTLV-1 transformed T lymphocyte line (Ab-VDR) established from a patient with vitamin D-resistant rickets type II with undetectable 1,25(OH)2D3 cellular receptors are resistant to the action of 1,25(OH)2D3. Inhibition of GM-CSF expression by 1,25(OH)2D3 can occur independently of interleukin 2 regulation and is probably mediated through cellular 1,25(OH)2D3 receptors. We conclude that 1,25(OH)2D3 may be important in the physiology of hematopoiesis.

1 alpha,25-Dihydroxyvitamin D3 inhibits gamma-interferon synthesis by normal human peripheral blood lymphocytes

1 alpha,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the biologically active metabolite of vitamin D3, inhibited synthesis of gamma-interferon (IFN-gamma) by phytohemagglutinin-activated peripheral blood lymphocytes (PBLs). A significant reduction of IFN-gamma protein levels in PBL culture medium was achieved with a physiologic 1,25-(OH)2D3 concentration (0.1 nM). 1,25-(OH)2D3 also inhibited accumulation of IFN-gamma mRNA in activated PBLs in a dose-dependent fashion. The ability of 1,25-(OH)2D3 to modulate IFN-gamma protein synthesis was unaltered in the presence of high concentrations of recombinant human interleukin 2. The suppression of IFN-gamma synthesis by PBLs was specific for 1,25-(OH)2D3; the potencies of other vitamin D3 metabolites were correlated with their affinities for the cellular 1,25-(OH)2D3 receptor. The time course of 1,25-(OH)2D3 receptor expression in phytohemagglutinin-activated PBLs was correlated with the time course of 1,25-(OH)2D3-mediated inhibition of IFN-gamma synthesis. In selected experiments, T-lymphocyte-enriched cell preparations were utilized. In these experiments, 1,25-(OH)2D3 was equally active as in PBL preparations. Finally, we examined the effects of 1,25-(OH)2D3 on the constitutive IFN-gamma production by two human T-lymphocyte lines transformed by human T-lymphotropic virus type I. The cell lines were established from a normal donor (cell line S-LB1) and from a patient with vitamin D-dependent rickets type 2 (cell line Ab-VDR). IFN-gamma synthesis by S-LB1 cells was inhibited in a dose-dependent fashion by 1,25-(OH)2D3, whereas IFN-gamma synthesis by Ab-VDR cells was not altered by 1,25-(OH)2D3. The data presented in this study provide further evidence for a role of 1,25-(OH)2D3 in immunoregulation.

Synthesis and biological activity of 1 alpha,23,25,26-tetrahydroxyvitamin D3

The metabolic pathway from 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3] to 1 alpha,25-dihydroxyvitamin D3-26,23-lactone includes the formation of 1 alpha,23,25-26-tetrahydroxyvitamin D3 [1 alpha,23,25,26-(OH)4D3]. The aim of the current study was to explore the as yet unknown biological properties of this vitamin D3 sterol. The four diastereoisomers of 1 alpha,23,25,26-(OH)4D3 were chemically synthesized. They were compared to 1 alpha,25-(OH)2D3 in terms of their affinity for the chick intestinal 1 alpha,25-(OH)2D3 receptor and their biologic activity in vivo (stimulation of intestinal calcium absorption and mobilization of calcium from bone in vitamin D-deficient rats). The 1,25-(OH)2D3 receptor binding affinities of 1 alpha,23(R)25(R)26-(OH)4D3, 1 alpha,23(S)25(S)26-(OH)4 D3, 1 alpha,23(S)25(R)26-(OH)4D3, and 1 alpha,23(R)25(S)26-(OH)4D3 were 11, 100, 216, and 443 times weaker than the binding affinity of 1 alpha,25-(OH)2D3, respectively. Compared to 1 alpha,25-(OH)2D3, the relative capacities of the 1 alpha,23,25,26-(OH)4D3 compounds to stimulate intestinal calcium absorption were 1/4 for 1 alpha,23(R)25(R)26-(OH)4D3; 1/19 for 1 alpha,23(S)25(S)26-(OH)4D3; 1/90 for 1 alpha,23(S)25(R)26-(OH)4D3; and 1/136 for 1 alpha,23(R)25(S)26-(OH)4D3. Maximal stimulation of intestinal calcium transport occurred 8 h after administration of vitamin D3 metabolites. Mobilization of calcium from bone was quantitated by serum calcium concentration measurements. The activities of 1 alpha,23(R)25(R)26-(OH)4D3, 1 alpha,23(S)25(S)26-(OH)4D3, 1 alpha,23(S)25(R)26-(OH)4D3, and 1 alpha,23(R)25(S)26-(OH)4D3 to increase serum calcium were estimated to be 4, 13, 43, and 69 times weaker than that of 1 alpha,25-(OH)2D3, respectively. These results illustrate the stereospecificity of the chicken intestine 1 alpha,25-(OH)2D3 receptor for binding of 1 alpha,23,25,26-(OH)4D3 and suggest that the 1 alpha,23,25,26-(OH)4D3 exerts its biological activity in the rat through an interaction with 1,25-(OH)2D3 receptors. In summary, the 1 alpha,23,25,26-(OH)4D3 had a markedly lower biological activity than 1 alpha,25-(OH)2D3.

25-Hydroxyvitamin D3 metabolism by lipopolysaccharide-stimulated normal human macrophages

Cultured normal human pulmonary alveolar macrophages and peripheral blood monocyte-derived macrophages were studied for their capacity to metabolize [3H]25-hydroxyvitamin D3 (25OHD3). Incubation of macrophages with bacterial lipopolysaccharide (LPS) resulted in the conversion of [3H]25OHD3 to a more polar vitamin D3 metabolite (up to 15 pmol/10(6) cells). Untreated macrophages did not synthesize this metabolite. Several findings suggested that the metabolite was the biologically active form of vitamin D3, namely 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. (1) The metabolite comigrated with chemically synthesized 1,25-(OH)2D3 on four different high performance liquid chromatographic systems. (2) The metabolite had the same affinity for the chick intestinal 1,25-(OH)2D3 receptor as authentic 1,25-(OH)2D3. (3) The biological activity of the macrophage metabolite in vivo (stimulation of intestinal calcium absorption and bone calcium mobilization in rachitic chicks) was identical to the activity of chemically synthesized 1,25-(OH)2D3. The LPS-stimulated synthesis of the 1,25-(OH)2D3-like compound by macrophages was dose dependent in a linear fashion; a half-maximal response was typically found with 100-200 ng LPS/10(6) cells. Polymyxin B abolished the effects of LPS on 25OHD3 metabolism in macrophages. Our data suggest that LPS-stimulated macrophages can modulate, on a local level, the function of 1,25-(OH)2D3-responsive cells by releasing the 1,25-(OH)2D3-like metabolite.

Metabolism of 25-hydroxycholecalciferol in human promyelocytic leukemia cells (HL-60). Isolation and identification of (5Z)- and (5E)-19-nor-10-oxo-25-hydroxycholecalciferol

Human promyelocytic leukemia cells incubated with 25-hydroxy[26,27-methyl-3H] cholecalciferol (1 microCi) or non-radioactive 25-hydroxycholecalciferol (550 micrograms) produced significant quantities of two vitamin D3 metabolites. The two metabolites were isolated and purified by methanol chloroform extraction and a series of chromatographic procedures. The metabolite purification and elution positions on these columns were followed by radioactivity and their ultraviolet absorption at 310 nm. The two metabolites have been unequivocally identified as (5Z)- and (5E)-19-nor-10-oxo-25-hydroxycholecalciferol by ultraviolet absorption spectrophotometry, mass spectrometry, Fourier-transform infrared spectrophotometry and co-chromatography with synthetic compounds on a high-performance liquid chromatograph. (5E)- but not (5Z)-19-nor-10-oxo-25-hydroxycholecalciferol was able to induce HL-60 cell phenotypic and functional differentiation. However, these two metabolites of 25-hydroxycholecalciferol did not bind specifically to the chick intestinal 3.7 S. receptor protein for 1 alpha,25-dihydroxycholecalciferol. The precise biological role of these metabolites is as yet unclear.

Regulation of 25-hydroxyvitamin D3 metabolism in a human promyelocytic leukemia cell line (HL-60): 1,25-dihydroxyvitamin D3 stimulates the synthesis of 24,25-dihydroxyvitamin D3

The human promyelocytic leukemia cell line HL-60 undergoes macrophage-like differentiation after exposure to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the biologically active metabolite of vitamin D3. In the current study, we demonstrate that 1,25(OH)2D3 also regulates 25-hydroxyvitamin D3 [25(OH)D3] metabolism in HL-60 cells. The presence of 1,25(OH)2D3 in the culture medium of HL-60 cells stimulated the conversion of 7-10% of the substrate [25(OH)D3] to a more polar metabolite, which was identified as 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] from the elution positions on sequential HPLC systems and the sensitivity to periodate treatment. The HL-60 subclone HL-60 blast, which is unresponsive to 1,25(OH)2D3 in terms of differentiation, also responded to 1,25(OH)2D3 treatment with the production of 24,25(OH)2D3. Maximal stimulation of 24,25(OH)2D3-synthesis (approximately 7 pmol/5 X 10(6) cells) in HL-60 cells was noted with a 12-h exposure to 10(-9) M 1,25(OH)2D3. The ability of vitamin D3 metabolites other than 1,25(OH)2D3 to induce the synthesis of 24,25(OH)2D3 in HL-60 cells was, with the exception of 1 alpha-hydroxyvitamin D3, in correlation with their reported affinities for the specific 1,25(OH)2D3 receptor which is present in HL-60 cells. Treatment of HL-60 cells with phorbol diesters abolished the 1,25(OH)2D3 responsiveness, while treatment with dimethylsulfoxide and interferon gamma did not markedly alter the 25(OH)D3 metabolism of HL-60 cells. Small amounts (approximately 1% of substrate) of two 25(OH)D3 metabolites, which comigrated with 5(E)- and 5(Z)-19-nor-10-keto-25-hydroxyvitamin D3 on two HPLC solvent systems, were synthesized by HL-60 cells, independently from 1,25(OH)2D3 treatment or stage of cell differentiation. Our results indicate that 1,25(OH)2D3 influences 25(OH)D3 metabolism of HL-60 cells independently from its effects on cell differentiation.

gamma-Interferon stimulates production of 1,25-dihydroxyvitamin D3 by normal human macrophages

We show for the first time that normal human pulmonary alveolar macrophages (PAM) markedly enhance their basal rate of the production of [3H]-1,25(OH)2D3 when cultured in the presence of recombinant gamma-interferon (gamma-IFN). The rate of conversion of [3H]-25(OH)D3 to [3H]-1,25(OH)2D3 was dose-dependent in a linear fashion. A maximal production of 1,25(OH)2D3 by PAM occurred after exposure of PAM to gamma-IFN for one day. This maximum plateau-level was sustained for at least five days. The authenticity of the putative 1,25(OH)2D3 obtained from PAM was tested by demonstrating the exact comigration of [3H]-1,25(OH)2D3 with chemically synthesized 1,25(OH)2D3 in four different HPLC-systems.

A sensitive and simplified radioimmunoassay for 1,25-dihydroxyvitamin D3

A sensitive radioimmunoassay system for 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] with an improved extraction procedure has been developed. Following one-step extraction and prepurification of 1,25(OH)2D3 by 'Extrelut-1' minicolumns final purification was achieved by high-performance liquid chromatography (HPLC) using a radial compression separation system equipped with a mu Porasil cartridge. The HPLC method applied allows the purification of 4 extracts/h. Recovery of 1,25(OH)2[3H]D3 after HPLC was 77 +/- 2.6% (mean +/- SD, n = 51). Since the recovery of 1,25(OH)2[3H]D3 was very reproducible, addition of labelled steroid to each single serum sample for monitoring recovery was omitted. The sensitivity of the assay was 0.8 pg/tube resulting in a detection limit of 3 ng/l, when 1 ml of serum was extracted. Intra-assay and inter-assay coefficients of variation were 12% and 16.8%, respectively. Serum 1,25(OH)2D3 concentration in 30 normal subjects (mean age: 25 yr) was 55 +/- 12 ng/l (mean +/- SD). In 55 elderly patients (mean age: 77 yr) the 1,25(OH)2D3 serum level was 32 +/- 12 ng/l (mean +/- SD) and in three patients with chronic renal failure on 1,25(OH)2D3 therapy 146 +/- 67 ng/l (mean +/- SD). Patients with chronic renal failure had reduced 1,25(OH)2D3 serum levels (mean 5.4 ng/l, range less than 3-11 ng/l, n = 10). In one patient with renal failure, following kidney transplantation the serum 1,25(OH)2D3 and creatinine levels were monitored from the 4th to the 12th post-surgical day: a highly significant negative correlation (r = 0.85) was found.

Serum dopamine-beta-hydroxylase in psychiatric patients and normals. Effect of d-amphetamine and haloperidol

Serum dopamine-beta-hydroxylase activity was estimated in groups of normals and of psychiatric patients, using a thin layer radiochromatographic method. The percentage of patients with schizophrenic and with depressive symptomatology was higher in the population with high enzyme activities. In addition, d-amphetamine given to normals caused an increase in the serum activity while haloperidol caused the opposite effect. The activity in serum is interpreted as a loss in the enzyme from the place it acts physiologically, with possible influence on the noradrenaline synthesis rate.

Delay in diastolic restitution of full myocardial contractility in guinea pig atrium

In an isolated perfused left atrium of guinea pig, pressure amplitudes were recorded at 37 degrees C and a stimulation rate of 240/min with interposed variable resting pauses. After prolonged intervals the preparation develops maximum pressure, which does not depend on perfusion time or on any positive inotropic intervention. The latter is found to shorten the time needed for restitution of full contractility. Nifedipine (5 X 10(-7)M) exerts its negative inotropic effect mainly by a delay in restitution time; acetylcholine (2 X 10(-7)M), by a concomitant reduction of all pressure amplitudes over the whole range of stimulus intervals. The latter effect is similar to that of lowering [Ca2+]o.

[Prefabricated complex wire replacement of middle ear ossicles (author's transl)]

This article comments on two prefabricated and linked complexes of wire that were used to replace the malleus and incus, and the malleus, incus and stapes.

The effect of isolation on myocardial properties

Denervation deprives the heart of its normal adrenergic and cholinergic control via the sympathetic and parasympathetic pathways. In a heart which is blood supplied by a donor animal of the same species, normal contractility is maintained, probably by blood borne catecholamines or possibly by unknown inotropic agents of the donor. A heart receiving blood oxygenated by isolated lungs is in a state of failure. Substitution of blood by a cell and protein free solution diminishes oxygen availability in cardiac muscle, both in the perfused and bathed preparation. In the unphysiological environment, myocardial cells lose K+ and gain Na+. Under best possible conditions of oxygen supply but in a later stage of perfusion, contractility during rhythmical stimulation is depressed more at lower than at higher rates. Frequency potentiation and the inotropic effectiveness of noradrenaline is more pronounced in vitro than in situ. In excised papillary muscles and ventricular and atrial strips, the disarrangement and a more or less severe lesion of individual fibres accelerates the decay in mechanical performance. The role of endogenous catecholamines for the maintenance of normal contractility in situ and in vitro is still a matter of discussion.

Time- and rate-dependence of the inotropic action of noradrenaline in the isolated guinea-pig's atrium

The inotropic action of noradrenaline (10-6 mol/l)) was studied on a left guinea-pig's atrium which was isolated functionally by ligations and perfused during artificial stimulation (basal rhythm: 120/min) over a period of 5 to 10 hrs. Each half hour the rate was varied within a range from 60 to 300 imp/min.

RESULTS

When modernaline is applied continuously throughout the experienment, contractility in terms of amplitude and rate of pressure development is almost maintained on the control level at the stimulation rates over at least 4 hrs of perfusion. When noradrenaline is applied at various stages of perfusion it compensates for the foregoing decay of contractility even after 8 hrs. Since contractility during normal perfusion decreases much more at a lower than at a higher rate the inotropic action of noradrenaline is minimal at a high rate in the fresh preparation (this means: under physiological conditions) and is fully developed only during later stages of perfusion at a low rate (which is far below the physiological range.