Steroid diffusion across membrane

The mechanisms of mineralization are not fully understood. Fluorescent, low-molecular weight compounds such as tetracycline or calcein bind strongly to bone mineral, when administered for short periods. They then accumulate in narrow bands in the new bone. [28] These bands run across the contiguous group of bone-forming osteoblasts. They occur at a narrow (sub- micrometer ) mineralization front. Most bone surfaces express no new bone formation, no tetracycline uptake and no mineral formation. This strongly suggests that facilitated or active transport , coordinated across the bone-forming group, is involved in bone formation, and that only cell-mediated mineral formation occurs. That is, dietary calcium does not create mineral by mass action.

Because non-genomic pathways include any mechanism that is not a genomic effect, there are various non-genomic pathways. However, all of these pathways are mediated by some type of steroid hormone receptor found at the plasma membrane. [13] Ion channels, transporters, G-protein coupled receptors (GPCR), and membrane fluidity have all been shown to be affected by steroid hormones. [9] Of these, GPCR linked proteins are the most more information on these proteins and pathways, visit the steroid hormone receptor page.

Various steroids diffused readily through dimethylpolysiloxane membrane into distilled water at 37°C. The diffusion was found to be proportional to the thickness of the membrane and its area. Calculated values for standard conditions ( μ g/24 hrs/100mm 2 /) were as follows: 19 norpregn-4-ene-3, 20-dione, 1353; pregn-4-ene-3, 20-dione, 469; 17β-hydroxyandrost-4-en-3-one, 317; 6-methyl-17 α -acetoxypregna-4, 6-diene-3, 20-dione, 236; 17 α -ethynyl-17β-hydroxyestr-4-en-3-one, 73; estra-1, 3, 5(10)-triene-3, 17β-diol, 61; 3-methoxy-17 α -ethynylestra-1, 3, 5(10)-trien-17β-ol, 43; 11β, 21-dihydroxypregn-4-ene-3, 20-dione, 21; 11β, 17 α , 21-trihydroxypregn-4-ene-3, 20-dione, 6. The rates of diffusion through other polymers (acetylcellulose, fluoroethylene, polyester, polycarbonate, polyethylene, polyamid, and polystyrene copolymer) were of the order of 1% or less.

Steroid diffusion across membrane

steroid diffusion across membrane

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