The modulation of transcobalamin II (TC-II) production by cyclic adenosine 3',5'-monophosphate in the murine macrophage cell line J774: relationship to growth behavior.

We undertook a study to define the role of cyclic AMP [cAMP] in modulating the secretion of transcobalamin II (TC-II) in the mouse macrophage like cell line J774. J774 was observed to secrete large amounts of TC-II, particularly in the presence of 8-bromo cAMP or cholera toxin or when grown in medium supplemented with low concentrations of horse serum (1% or 5%) or in serum-free medium. Variant cell lines derived from J774 and deficient either in adenylate cyclase (ac -) or cAMP-dependent protein kinase (pk -) activity showed very low and intermediate levels of basal secretory activity of TC-II, respectively, compared to J774.

Serum transcobalamin levels as an early indicator of bone marrow engraftment following transplantation.

Three B12 binding proteins, the transcobalamins TCI, TCII and TCIII, were determined serially in the serum of five patients who underwent bone marrow transplantation. The increase in TCII, followed by the increase in TCI, proved to be an early indicator of bone marrow regeneration, reaching a peak of up to twice its normal levels at least 5 d prior to the rise of the peripheral white blood cell count.

Prognostic significance of changes in serum transcobalamin levels in cancer patients with chemotherapy-induced granulocytopenia.

Serum transcobalamin (TC) levels were determined daily in 14 adults suffering from advanced nonhematological malignancies and hospitalized because of chemotherapy-induced leukopenia and fever. Even during the nadir leukocyte count, TCI and TCIII serum levels were normal or only slightly decreased indicating that bone marrow activity was not completely suppressed. A significant increase in serum TCII level was observed in all patients, with peak values occurring an average of 4.

Effect of dexamethasone on serum transcobalamin II concentration in women undergoing pelvic surgery.

Dexamethasone (120 mg/day for 2 days) was administered intramuscularly to young females undergoing pelvic surgery for infertility. The therapy was shown to cause a transient increase in the serum level of the granulocyte-produced transcobalamins (TCI and TCIII) and more significantly in the monocyte-produced transcobalamin (TCII), from 1220 +/- 70 to 1980 +/- 158 pg/ml (P less than 0.001).

Production of transcobalamin II by various murine and human cells in culture.

The ability of various murine and human cell types to secrete in vitro transcobalamin II (TCII), the vitamin B12 transport protein, was investigated. All cell types tested were found to secrete into the culture medium biologically active TCII molecules, capable of facilitating B12 uptake. The largest amounts of TCII were produced by primary cultures of murine fibroblasts and macrophages.