PubMed · 7005964
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P A Anderson. 1980. Epithelial conduction: its properties and function.. https://doi.org/10.1016/0301-0082(80)90022-2
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To detect high density lipoprotein binding proteins, a new ligand blotting method that uses apolipoprotein AI-dinitrophenol as a ligand was established. Apolipoprotein AI-dinitrophenol was prepared by incubating the mixture of apolipoprotein AI and 2,4-dinitrobenzene sulfonic acid sodium salt at pH 8.5. Four to six dinitrophenol groups were found to be conjugated with an apolipoprotein AI molecule without any obvious impairment of its binding activity to the binding proteins. By this detection procedure, we detected two apolipoprotein AI binding proteins in plasma membrane fractions from bovine liver and adrenal cortex with molecular masses of 120 kDa and 95 kDa. Since this new ligand blotting method is simple and time-saving, it is expected to become a useful tool in the studies on high density lipoprotein binding proteins.
OBJECTIVE: To determine what effects long-term phenobarbital administration to dogs with epilepsy would have on serum biochemical factors and adrenocortical function. DESIGN: Prospective, uncontrolled study. ANIMALS: Five dogs with idiopathic epilepsy. PROCEDURE: Serum total protein, albumin, total bilirubin, and cholesterol concentrations and serum alkaline phosphatase and alanine aminotransferase activities were measured before and 2 weeks, 6 months, and 12 months after initiation of phenobarbital administration. Endogenous ACTH concentration was measured, and ACTH stimulation and low-dose dexamethasone suppression tests were performed at the same time. RESULTS: Serum albumin concentration decreased in 4 of 5 dogs, and serum cholesterol concentrations decreased in all 5 dogs over the course of the study. Serum alkaline phosphatase concentration and alanine aminotransferase activities increased over time, and were greater than the upper reference limits in 4 of the 5 dogs by the end of the study. Endogenous ACTH concentration increased in all dogs but remained within reference limits. Plasma ACTH-stimulated aldosterone concentration increased over the course of the study. Plasma cortisol concentration did not suppress, after administration of dexamethasone in 1 dog after 6 and 12 months of phenobarbital administration. CLINICAL IMPLICATIONS: Although endogenous ACTH concentration should be normal in dogs receiving phenobarbital, results of ACTH stimulation and dexamethasone suppression tests may be altered. Serum albumin and cholesterol concentrations, and serum alkaline phosphatase and alanine aminotransferase activities may also be abnormal.
Microsomal cytochrome P450c17 catalyzes both steroid 17 alpha-hydroxylase activity and scission of the C17-C20 steroid bond (17,20-lyase) on the same active site. Adrenal 17 alpha-hydroxylase activity is needed to produce cortisol throughout life, but 17,20-lyase activity appears to be controlled independently in a complex, age-dependent pattern. We show that human P450c17 is phosphorylated on serine and threonine residues by a cAMP-dependent protein kinase. Phosphorylation of P450c17 increases 17,20-lyase activity, while dephosphorylation virtually eliminates this activity. Hormonally regulated serine phosphorylation of human P450c17 suggests a possible mechanism for human adrenarche and may be a unifying etiologic link between the hyperandrogenism and insulin resistance that characterize the polycystic ovary syndrome.