In vitro model of parathyroid hormone-related protein secretion from mammary cells isolated from lactating cows

Hormonal and dietary regulation of changes in bone density during lactation and after weaning in women

Lactating women secrete approximately 250 mg of calcium in breast milk each day. Some of the calcium used for milk production comes from bone as women experience a transient 3-9% decrease in bone density during lactation. This loss appears to be obligatory and under hormonal regulation as lactation-induced bone loss occurs even when calcium intake is high. Bone mineral is recovered after lactation ceases or menses resume. Recovery of bone mineral appears to be complete even when pregnancies and lactations are closely spaced, and lactation does not increase future risk of osteoporotic fracture. Current data point to estrogen and parathyroid hormone-related peptide as regulating bone mobilization during lactation. The typical calcium regulatory hormones, parathyroid hormone, calcitriol and calcitonin, do not appear to stimulate bone resorption during lactation. Restoration of ovarian hormone production and decreased production of PTHrP2 are likely to result in the recovery of bone mineral after lactation has ceased.

Effects of isoprothiolane on cell growth of cultured bovine mammary epithelial cells

This study was performed to investigate the effects of isoprothiolane on cell growth and the production of interleukin (IL)-1 and IL-6 by bovine mammary epithelial cells in vitro. Isoprothiolane increased proliferation of mammary epithelial cells in a dose-dependent manner at the concentration of 0.05 to 5 microM when cultured either with or without serum-supplemented medium. In contrast, isoprothiolane (0.0005-5 microM) significantly inhibited the production of IL-1 and IL-6 by mammary epithelial cells. Moreover, the cytokines, IL-1alpha, IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha tended to inhibit the proliferation of mammary epithelial cells in a dose-dependent manner. These results indicated that isoprothiolane regulated mammary epithelial cell growth in vitro possibly by modulating the production of cytokines.

Effects of lipopolysaccharide on production of interleukin-1 and interleukin-6 by bovine mammary epithelial cells in vitro

This investigation was performed to determine the effect of lipopolysaccharide (LPS) on production of interleukin (IL)-1 and IL-6 by bovine mammary epithelial cells in vitro. After confluence, the cells were stimulated with LPS (0.1, 1.0 or 10 micrograms/ml) for 4, 8, 24, and 48 hr. LPS increased production of both IL-1 and IL-6 production from mammary cells in a dose dependent manner. The expression of mRNA for IL-1 receptor antagonist (IL-1ra) was demonstrated by reverse transcription-polymerase chain reaction in bovine mammary epithelial cells.

Detection of interleukin-1 and interleukin-6 on cryopreserved bovine mammary epithelial cells in vitro

This investigation was performed to determine whether primary cultures of mammary cells from lactating cows would sustain production of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF), and express mRNA for cytokines interleukin (IL)-1alpha, IL-1beta, IL-2, IL-4, IL-6, IL-10, interferon (INF)-tau, TNF-alpha, and granulocyte-macrophage colony-stimulating factor (GM-CSF) by the reverse transcription-polymerase chain reaction (RT-PCR) in vitro. Cryopreserved mammary epithelial cells collected from cows at 1 week post calving were plated in collagen-coated 24-well culture plates (250,000 cells/well). IL-1 and IL-6 productions were measured using a A375 cell growth inhibition assay and a 7TD1 hybridoma proliferation assay, respectively. Production of IL-1 was demonstrated in mammary epithelial cells cultured with unsupplemented medium, but was not produced by cells cultured in medium supplemented with fetal bovine serum. IL-6 production in the conditioned medium was continued at steady level until day 14, whereas IL-6-like bioactivity was not detected in medium alone. TNF-like activity was not detectable in any experiments. This study also demonstrated the expression of mRNA for multiple cytokines including IL-1alpha, IL-1beta, IL-6, IL-10, TNF-alpha, and GM-CSF by RT-PCR in mammary cell cultures. The results indicate that bovine mammary epithelial cells of lactating cows produce IL-1 and IL-6 and have gene expression for multiple cytokines. This in vitro model will be useful to investigate the function and regulation of IL-1 and IL-6 in the lactating mammary gland.