Características do trato digestivo, metabolizabilidade e retenção de nutrientes em frangos de corte alimentados com complexo enzimático / Characteristics of the digestive tract, metabolizability and nutrient retention in broilers fed enzymatic complex

The objective was to evaluate the digestive tract characteristics, metabolizability and nutrient retention of broilers fed diets supplemented with enzyme complex (EC). To evaluate the characteristics of the digestive tract 600 female Cobb 500 birds were used, distributed in a completely randomized design, with 5 inclusion levels of the EC (0; 100, 200, 300 and 400 g/ton) and 6 replicates of 20 birds each. To evaluate the metabolizability and the retention of nutrients 200 female Cobb 500 birds at 15 days of age were used, distributed in a completely randomized design with 5 levels of supplementation of the EC and 4 replicates of 10 birds each. No significant effects (P>0.05) were observed for the supplementation of the EC in the intestinal pH, digestive organ weight, intestinal length and metabolizable coefficients of dry matter and crude protein. The metabolizable coefficient of ethereal extract was influenced in a quadratic decreasing form (P<0.01). The metabolizable coefficients of calcium (Ca) and phosphorus (P) were influenced in a quadratic increase (P<0.01), resulting in increased Ca retention in 21.39% and P in 9.56%. Supplementation of the EC in broiler diets improves the metabolizability and retention of P and Ca, without affecting the other parameters evaluated.(AU)

Active-site-directed photoaffinity radioiodination of androgen-binding proteins.

Androgen-binding protein (ABP) in rat epididymal cytosol and sex hormone-binding globulin (SHBG) in rabbit serum and SHBG purified from human serum were active-site-directed photoaffinity radiolabeled with 17 alpha-[(E)-2-[125I]iodoethenyl]androstan-4,6-dien-17 beta-ol-3-one ([125I]1). The interaction of this compound with binding components in epididymal cytosol was dependent on exposure of the mixture to ultraviolet light and on the duration of exposure. Photolysis in the presence of [125I]1 and 5 alpha-dihydrotestosterone (5 alpha-DHT) resulted in a 40% inhibition of binding of [125I]1 to cytosolic components. These result indicate that, while [125I]1 interacted with 5 alpha-DHT binding sites, it also formed adducts with other sites. To characterize the labeled species, the photolysis mixture was subjected to electrophoresis under denaturing and reducing conditions. Autoradiography of the gel revealed that ABP and SHBG were labeled with [125I]1, but in cytosol and serum, higher and lower molecular weight components were also labeled. Purified SHBG was labeled, but no labeled contaminating protein was detected. The presence of 5 alpha-DHT completely inhibited [125I]1 photolabeling of human and rabbit SHBG and of ABP. However, in cytosol, the presence of 5 alpha-DHT also eliminated photolabeling to a component that may be albumin, but 5 alpha-DHT did not affect [125I]1 photolabeling of other contaminating proteins in cytosol. Thus, while [125I]1 is an effective photoaffinity radiolabel for ABP and SHBG, the observation that it also photolabels other proteins limits its practical use to the radiolabeling of purified ABP and SHBG preparations.

Preparation of 17 alpha-iodoethynylandrosta- and 17 alpha-(2-iodoethenyl)androsta-4,6-dien-17 beta-ol-3-ones as active site-directed photoaffinity ligands for androgen-binding proteins.

Unsaturated analogues of androst-4-en-17 beta-ol-3-one, each with a 17 alpha-iodoethynyl or 17 alpha-(2-iodoethenyl) substituent, were prepared, and their relative binding affinities (RBAs) for androgen-binding protein (ABP) were compared with those of 5 alpha-androstan-17 beta-ol-3-one, androst-4-en-17 beta-ol-3-one, androsta-4,6-dien-17 beta-ol-3-one, and androsta-1,4,6-trien-17 beta-ol-3-one. These binding studies indicate that the iodine[125I] analogues of 17 alpha-iodoethynyl and 17 alpha-[(E)-2-iodoethenyl] derivatives of androsta-4,6-dien-17 beta-ol-3-one and androsta-1,4,6-trien-17 beta-ol-3-one will have RBAs at least twice as great as that of 5 alpha-androstan-17 beta-ol-3-one. They can be prepared from 17 alpha-ethynylandrosta-4-en-17 beta-ol-3-one, the final synthetic step using N-[125I]iodosuccinimide, and are potential radioiodinated, active site-directed photoaffinity ligands for ABP and testosterone-binding globulin.

Tissue-specific pharmacology of testosterone and 5 alpha-dihydrotestosterone analogues: characterization of a novel canine liver androgen-binding protein.

The mechanism by which the hormones 5 alpha-dihydrotestosterone and testosterone differentially regulate such diverse functions as development of male internal and external genitalia and maintenance of prostatic growth via a single androgen receptor (AR) is not well understood. To search for potential AR isoforms, an extensive pharmacological survey of the binding of [3H]mibolerone (7 alpha,17 alpha-[3H]dimethyl-19-nortestosterone) in dog prostate, adrenal gland, testis, liver, kidney, brain, muscle, and spleen cytosolic extracts was carried out. The antagonist androst-4-en-3,17-dione (ATD), as well as a series of unsaturated analogues of testosterone, exhibited marked tissue specificity for binding to mibolerone-binding proteins (MBPs), with ATD having a 10-fold higher affinity for the MBPs present in liver than for those in prostate and testis. The difference in affinity was not due to tissue-specific metabolism of ATD. Competition binding profiles for ATD with mixtures of prostate and liver extracts were consistent with two distinct populations of binding sites. Both wild-type human AR-B and the recently discovered human AR-A isoform were expressed in COS cells and were found to exhibit pharmacology similar to that of the prostatic MBPs in dogs. Analogues of ATD or testosterone could prove to be useful probes for delineating the differential effects of 5 alpha-dihydrotestosterone and testosterone on the biological actions of the AR and related proteins.