Thomas L. Clemens

1 alpha,25-dihydroxyvitamin D3 induces maturation of the human monocyte cell line U937, and, in association with a factor from human T lymphocytes, augments production of the monokine, mononuclear cell factor.

The monocyte factor, interleukin 1, or other factors homologous with interleukin 1, modulates functions of a variety of cells, including T and B lymphocytes, synovial cells, and chondrocytes. We have reported that a human monocyte cell line, U937, produces interleukin 1 when incubated with a soluble factor from lectin-stimulated T lymphocytes. We have also shown that U937 cells have a specific cytosolic receptor for 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25[OH]2D3). We now report that 1 alpha,25(OH)2D3(10(-11)-10(-10) M) induces maturational changes in the U937 cells similar to those produced by conditioned medium from lectin-stimulated T lymphocytes (increase in Fc receptors and OKM1 binding and decrease in proliferation), but does not induce monokine production as measured by mononuclear cell factor activity. 1 alpha,25(OH)2D3 is 200-300-fold more effective than 25-hydroxyvitamin D3, which is consistent with the known biological potency of these vitamin D3 metabolites. 1 alpha,25(OH)2D3 and the lymphokine together markedly augment maturational effects and, in addition, augment monokine production. The specificity of the interaction is further demonstrated by the lack of augmentation of monokine production with 1 beta,25-dihydroxyvitamin D3 in the presence of lymphokine. These interactions of a classical hormone and the hormonelike product(s) of the immune system with U937 cells serve as a model for human monocyte/macrophage differentiation and suggest a role for these interactions in some aspects of inflammation.

Measurement of circulating vitamin D in man.

An assay for vitamin D consisting of high-pressure liquid chromatography (HPLC) and ultraviolet (UV) absorbance detection has been developed and used to measure circulating vitamin D concentrations in human subjects during summer and winter and after deliberate exposure to ultraviolet radiation. Extracts of 2-4 ml of serum were initially fractionated on silica Sep-Pak cartridges followed by reverse-phase HPLC and finally quantitated by UV-absorbance during straight-phase HPLC. Using these methods, we determined the normal range for circulating vitamin D in Boston subjects to be less than 0.5 ng/ml to 25 ng/ml (n = 30); subjects sampled during summer months had higher concentrations of vitamin D than those sampled during winter months. In subjects exposed to a single quantitative dose of ultraviolet radiation (UVR), large transient increases in circulating vitamin D3 were observed. Concentrations rose 30-50 fold over the first days after exposure before returning to basal levels by one week.

Tumor-induced osteomalacia: Kinetics of calcium, phosphorus, and vitamin D metabolism and characteristics of bone histomorphometry

A patient with a mesenchymal tumor and hypophosphatemic osteomalacia was studied before and after tumor excision. Initial laboratory values included normal serum calcium, decreased serum phosphorus and tubular reabsorption of phosphate, undetectable 1,25-dihydroxyvitamin D, and normal parathyroid hormone. Histomorphometry of a bone biopsy specimen showed evidence of increased osteoclastic bone resorption. By 16 hours after tumor removal, 1,25-dihydroxyvitamin D level had normalized, but serum phosphorus level was unchanged; at 28 hours, both serum phosphorus value and tubular reabsorption of phosphate were within normal limits. It is concluded that tumor removal is associated with rapid correction both of 1,25-dihydroxyvitamin D production and of renal phosphate wasting. Increased bone resorption suggests the production of an osteoclast activator by the tumor and may explain the typically normal serum calcium value in this disorder.

Exogenous Calciferol (Vitamin D) and Vitamin D Endocrine Status among Elderly Nursing Home Residents in the New York City Area

Objective: To determine the role and relative importance of sources of exogenous calciferol (vitamin D) in maintaining vitamin D endocrine status in the mid‐winter and early spring in a representative sample of institutionalized elderly persons in the New York City area.

Binding of 1,25-dihydroxy-[3H]vitamin D3 in nuclear and cytosol fractions of whole mouse skin in vivo and in vitro

Specific, cytosolic binding proteins for 1 ,25-(OH)2Da exist in the established target organs, e.g., intestine [ 1,2] and bone [3], as well as in other tissues [4-81, and these ‘receptors’ appear to transfer the hormone to the nucleus. A similar binding protein was detected in cytosol prepared from rat [9] and mouse skin [lo] suggesting the presence of a cutaneous 1 ,25-(OH)z-D,-receptor system. To study the mechanism of the interaction of 1 ,25-(OH)2-D3 with skin, we determined the distribution of the hormone within subcellular organelles in vivo and in vitro. Here, we report that 1 ,25-(OH)Z[3H] D3 injected in vivo preferentially accumulated in cytosol and nuclear fractions of whole mouse skin and that nuclear uptake of hormone in vitro was dependent on time and temperature of incubation. These results suggest the existence of an intracellular receptor system for 1 ,25-(OH)z-D3 in skin that is similar to the hormone’s receptor system in intestine and bone.

Vitamin B12 Deficiency and Bone Health

Mice deficient in vitamin B12 synthesis have growth retardation and a comparative paucity of osteoblasts. It seems that vitamin B12 interferes with growth hormone signaling in the hepatocyte and its downstream effects on the osteoblast.

A simple method for generation of antibodies with specificity for 1,25-dihydroxyergocalciferol and 1,25-dihydroxycholecalciferol

A simple method for production of antisera with high affinity and selectivity for 1 alpha, 25-dihydroxyergocalciferol and 1 alpha, 25-dihydroxychole-calciferol is described. 1 alpha-Hydroxy-25,26,27-trisnorcholecalciferol-24-oic acid was coupled directly to bovine serum albumin. Rabbits immunized with this conjugate rapidly produced antibodies that bound 3H-1 alpha,-25-dihydroxycholecalciferol with high affinity and demonstrated nearly equal reactivity with 1 alpha, 25-dihydroxyergocalciferol and poor reactivity with 25-hydroxycholecalciferol; 24,25-dihydroxycholecalciferol; 25,26-dihydroxycholecalciferol; and 1 beta,25-dihydroxycholecalciferol. The use of one of these antisera has led to the development of a specific assay for 1 alpha,25-dihydroxyergocalciferol and 1 alpha,25-dihydroxycholecalciferol in human serum.

New Directions for the Design of Parathyroid Hormone Antagonists

Peptide hormone antagonists that are effective in vivo are uniquely precise tools for biomedical research. They can be used to determine how peptide hormones act, what their role is in normal physiological processes, and how they contribute to pathophysiologic states.