Uptake and release of bilirubin by skin

1. Skin epithelium of albino rat, mouse and guinea pig was shown to accumulate bilirubin from a medium containing free or bound bilirubin. 2. The Km values for bound bilirubin were 2.22×10-3, 1.33×10-3 and 9.5×10-4m for rat, mouse and guinea pig respectively and the corresponding Km values for free bilirubin were 5.2×10-4, 4.0×10-4, 1.8×10-4m; the Vmax. values of bound and free bilirubin were unchanged. 3. The uptake showed saturation kinetics. Bound bilirubin was released together with serum proteins. Free bilirubin bound to skin was not released into the medium. 4. Freezing and thawing of skin epithelium did not cause any significant lowering of the uptake of bilirubin but heat-denatured skin epidermis took up only 50% of the bound bilirubin or free bilirubin taken up by control unheated skin epithelium. 5. The uptake of free and bound bilirubin was prevented by HgCl2 but not by sodium arsenate, NaCN, NaF, cycloheximide, 2,4-dinitrophenol or iodoacetate. 6. Most of the free bilirubin was bound to the lipids or lipoprotein fraction of skin epithelium and could be extracted by solvents. 7. Rat skin showed the highest accumulation and efflux of bilirubin

Role of human skin in the photodecomposition of bilirubin

1. Human skin epithelium and human skin were found to absorb both free bilirubin and serum-bound bilirubin from an aqueous buffered medium. The serum-bound bilirubin thus absorbed was readily released when human skin epithelium or human skin were transferred to media containing no bilirubin. 2. The Km values for serum-bound bilirubin were 1.8×10-3m and 2.2×10-3m respectively for human skin epithelium and human skin; corresponding Km values for free bilirubin were 3.0×10-4m and 5×10-4m. The Vmax. for bound and free bilirubin was of the same magnitude, the apparent Vmax. being 1.0 and 1.66mmol/g of tissue for human skin epithelium and human skin respectively. 3. When human skin that had acquired a yellow tinge by absorbing bilirubin was incubated in a buffered medium and exposed to a mercury-vapour light, the yellow colour disappeared and decomposition products of bilirubin accumulated in the medium. 4. Experiments with [3H]bilirubin indicated that the pigment absorbed by skin was photo-oxidized to products that were soluble in water and the quantity and number of such products increased with the time of exposure of human skin to the light-source. Under similar conditions [3H]bilirubin alone in buffered medium was also oxidized and gave products which by paper chromatography appeared to be different from those released by human skin that had absorbed bilirubin. 5. The results suggest that by virtue of its large surface area human skin can act as a matrix for the degradative action of light on bilirubin

A possible role of cyclic 3',5'-adenosine monophosphate in the germination of Cicer arietinum seeds

Changes in the activities of adenyl cyclase, cyclic AMP phosphodiesterase, protein phosphokinase, RNase, protease, DNA, RNA and protein synthesis during the initial imbibition phase of the germination cycle of Cicer arietinum (chick pea, Bengal gram) are reported. Activation of adenyl cyclase and phosphorylation of cellular proteins appears to precede RNA and protein synthesis in the imbibed seeds

Effect of cadmium on hepatic mixed-function oxidases during the early development of rats : possible protective role of metallothionein

Hepatic metallothionein contents and activities of mixed function oxidases in control and cadmium-treated rats (1.2 mg Cd2+/kg) of various age groups (7-, 14-, 21- and 90-days-old) were determined. A significantly high concentration of native metallothionein was noticed in immature rats (7- and 14-days-old). Cadmium administration induced metallothionein only in 21- and 90-day-old rats, while the basal level of native metallothionein of immature rats was not altered. Activity of certain mixed-function oxidases (MFO) such as aryl hydrocarbon hydroxylase, aminopyrine-N-demethylase, and benzphetamine-N-demethylase was inhibited significantly only in 21- and 90-day-old rats. Microsomal cadmium accumulation was significantly higher in adult as compared to immature rats. Results suggest a protective role of metallothionein against cadmium-induced inhibition of mixed-function oxidases in immature rats

Effect of bioamines on the cellular differentiation of Hartmannella culbertsoni

Epinephrine, 5-hydroxytryptamine, dopamine and tyramine induce axenic encystation of the free living amoeba Hartmannella culbertsoni. Cycloheximide inhibits encystation of amoeba mediated by the amines. The amines uniformly stimulate 3 to 4-fold the ability of the cells to synthesize cyclic 3',5'-adenosine monophosphate from adenosine triphosphate formed in situ. Epinephrine[14C] is bound to membranes of the amoeba (Kmof binding = 6.5 mM epinephrine). When amoebae are exposed to epinephrine, tyramine, dopamine or cAMP in a non-nutrient medium for 6 hr protein kinase activity is stimulated as evident from increased incorporation of 32P into cellular proteins

Conjugation of acrylamide with glutathione catalysed by glutathione-S-transferases of rat liver and brain

Acrylamide, an α , β unsaturated electrophile and a cumulative neurotoxin, was found to react with glutathione giving rise to an S-conjugate of acrylamide. Glutathione S-transferase of rat liver and brain cytosols (active on both acrylamide and 1-chloro 2,4 dinitrobenzene) emerged as a single major peak on elution from Sephadex G-75. The enzymic conjugation of acrylamide with glutathione increased with protein and was dependent on incubation time and pH of medium. Acrylamide inhibited glutathione-S-transferase activity towards 1-chloro 2,4-dinitro-benzene of both liver and brain cytosol, in a concentration and time dependent manner. Enzyme catalyzed conjugation of acrylamide with glutathione was induced significantly by phenobarbital and t-SO (tans-stilbene oxide). The enzymic conjugation of acrylamide increased two fold from neonatal to adult and then showed a decreasing pattern at subsequent ages