Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology最新文献

Bovine serum albumin (BSA) was exposed to hydroxyl radicals generated by the Fenton reaction. The reaction of the BSA solution with hydroxyl radicals resulted in a colour change from clear transparent to dark brown. The reaction was followed spectrophometrically. It was observed that during the reaction of BSA with hydroxyl radicals, a melanin-like absorption spectrum developed. The reaction with ferricyanide and the dark brown BSA solution resulted in the same dark blue-green colour as is typical for melanin. The results suggest that, by the reaction of BSA with hydroxyl radicals, melanin was formed.

This study was designed to validate an alternative in vitro system with isolated glomeruli of the Atlantic hagfish Myxine glutinosa as a model to study alterations in glomerular protein metabolisms in pharmaco-toxicology of anticancer drugs. A morphometric characterization of the glomeruli of Myxine glutinosa reveals a calculated glomerular volume of 180 nl/glomerulus. The glomerular extracellular volume, measured as inulin space, is 38.5 nl/glomerulus. Total glomerular protein content of Myxine glutinosa amounts to 3.56 micrograms/glomerulus and total DNA content to 0.44 microgram/glomerulus. Metabolic properties, estimated as glomerular protein synthesis, are comparable with mammalian glomeruli. The glomeruli of Myxine glutinosa are viable in a tissue culture for up to 12 hr. The incorporation rate of radiolabeled amino acids into glomerular, acid-precipitable proteins is almost identical to that of rats (e.g. Myxine glutinosa 1091 +/- 98 DPM/micrograms DNA vs. rat 1340 +/- 84 DPM/micrograms DNA after 4 hr incubation). To evaluate how nephrotoxic substances affect glomerular metabolism in this model, the anticancer drug Adriamycin (ADR) was used to experimentally induce a glomerular lesion. ADR caused an increase in glomerular protein synthesis in isolated glomeruli of Myxine glutinosa, which is in accordance with data found in rats. Cisplatin, in contrast, known to mainly interfere with tubular integrity, had no effect on glomerular protein synthesis, confirming the specificity of the model. The isolated glomeruli of Myxine glutinosa are suggested as a valid alternative multicellular in vitro system for studying alterations in glomerular metabolism under pharmaco-toxicological conditions and for the evaluation of specific target-cell toxicity of selected nephrotoxins.

The radioligand binding assay of A1 adenosine receptors in adipocyte crude plasma membrane from Yucatan miniature swine was optimized by evaluating 17 factors involved in the assay. Significant effects of CHAPS, adenosine deaminase, EDTA, pre-rinsing glass fiber filters and pH were found for the binding measurements. Using the optimized procedure, [3H]8-cyclopentyl-1,3-dipropylxanthine, ([3H]-DPCPX) binding to A1 adenosine receptors in swine subcutaneous adipocyte crude plasma membrane was measured; Bmax and Kd values were 479 +/- 77 fmol/mg protein and 0.87 +/- 0.10 nM, respectively. Values for mesenteric adipose tissue from sedentary swine and subcutaneous adipose tissue from exercise-trained swine were also measured.

The beta-subunit of the insulin receptor from the muscle of the shrimp Penaeus japonicus exists as multiple subtypes with M(r) of 79,000, 77,000 and 75,000. Only the subunit of M(r) 79,000 is autophosphorylated after the addition of insulin. The autophosphorylation occurred specifically at Tyr residues, as demonstrated by the specific subsequent dephosphorylation by the phosphotyrosyl protein phosphatase from the human placenta. The detergent, Triton X-100, and the metal ion, Mn2+, caused a noticeable enhancement of the autophosphorylation of shrimp insulin receptors from the muscle. Okadaic acid activated the kinase activity of the insulin-stimulated insulin receptor, but not the basal activity of the insulin receptor without the addition of insulin. Further studies comparing the insulin binding of the shrimp insulin receptor in the regulation of kinase activity of the multiple beta-subunit subtypes from the shrimp muscle are under way.