Biochemical profile and oocyte quality of primiparous Bos indicus cows submitted to a timed artificial insemination protocol.

The objective of this study was to verify the causes of the lower response of primiparous Bos indicus cows to the ovulation synchronization protocol. Two experiments were performed to evaluate the biochemical profile, oocyte and follicular cell quality (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, suckled primiparous (n = 24) and multiparous cows (n = 24) were submitted to ovum pick up (OPU). On Day 0 (D0), all cows received 2 mg of estradiol benzoate (EB) and an intravaginal progesterone insert (P4). Five days (D5) after the first hormonal administration (EB + P4), all follicles larger than 3 mm were counted on each ovary, and ovum pick-up (OPU) was performed. On day 12 (D12), the intravaginal progesterone insert was removed, and measurement and aspiration of the largest follicle were performed. Blood samples were collected on D5 and D12 to evaluate the concentrations of glucose, cholesterol, NEFA, IGF-1 and insulin. In Experiment 2, suckled primiparous (n = 50) and multiparous (n = 50) cows were subjected to an ovulation synchronization protocol based on E2/P4 (D0: 2 mg EB plus P4 intravaginal insert; D8: 500 µg of cloprostenol, 1 mg cypionate estradiol and 300UI of eCG; D10: artificial insemination). In addition, blood samples were collected on D10 for evaluation of the same hormones and metabolites described in Experiment 1. In all studies, calves remained with the cows during the experimental period. In experiment 1, the number of oocytes grade 1 (P = 0.83), grade 2 (P = 0.23) and grade 3 (P = 0.51), total number of retrieved oocytes (P = 0.14), oocyte quality index (P = 0.93) and total viable oocytes (P = 0.38) did not differ between primiparous and multiparous cows. The number of follicles at the time of follicular aspiration (20.7 ± 1.5 vs. 18.0 ± 1.9; P = 0.05) and the diameter of the largest follicle on D12 (13.5 ± 0.6 vs. 11.4 ± 0.6; P = 0.04) were greater in multiparous cows, and the number of degenerated oocytes was greater in primiparous cows (1.9 ± 0.7 vs. 1.2 ± 0.3; P = 0.05). On D5, the concentrations of IGF-1 (P = 0.47), insulin (P = 0.08), total cholesterol (P = 0.47), NEFA (P = 0.77) and glucose (P = 0.55) in the blood and IGF-1 (P = 0.97) and insulin (P = 0.11) in the follicular fluid did not differ between parity groups. On D12, there was no difference in the concentrations of IGF-1 (P = 0.26), total cholesterol (P = 0.32), NEFAs (P = 0.31) and glucose (P = 0.93) in the blood between primiparous and multiparous cows, however, the serum insulin concentration (P = 0.04) was higher in primiparous cows. There was no correlation between serum and follicular fluid insulin concentrations (r = 0.17; P = 0.31), however, there was a low correlation between serum and follicular fluid IGF-1 concentrations (r = 0.47; P = 0.002). Quantification of transcripts did not differ between parity groups. In experiment 2, concentrations of NEFA (P = 0.12) and insulin (P = 0.16) in the blood and P/AI (P = 0.93) did not differ between parity [60 % (30/50) primiparous vs. 60 % (30/50) multiparous]. In contrast, blood concentrations of IGF-1 (P = 0.0001), total cholesterol (P = 0.005) and glucose (P = 0.01) were greater in primiparous cows. It was concluded that the oocyte quality and expression of the genes evaluated in the granulosa cells were not different between primiparous and multiparous cows. Unexpectedly, the pregnancy rate did not differ between parity. Nevertheless, the blood concentrations of IGF-1, total cholesterol and glucose were greater in primiparous cows.

Padronização da quantificação do fator de crescimento semelhante à insulina I (IGF-I) em plasma bovino por ELISA / Standardization of ELISA for the measurement of Insulin-Like Growth Factor I (IGF-I) in bovine plasm

Esse estudo teve como objetivo a padronização de um ensaio imunoenzimático competitivo (cELISA) in house para a determinação das concentrações plasmáticas do fator de crescimento semelhante a insulina I (IGF-I) total para a espécie bovina, utilizando o sistema de amplificação biotina-estreptavidina peroxidase. O IGF-I foi extraído das proteínas ligadoras do fator de crescimento semelhante a insulina I (IGFBP), utilizando o tampão glicina acidificado seguido de neutralização do pH com hidróxido de sódio. As microplacas foram sensibilizadas com anti IgG de coelho, e as dosagens realizadas utilizando duas abordagens, um método com incubação prévia das amostras com o anticorpo anti-h-IGF-I e outro sem incubação prévia (adição simultânea de IGF-I biotilinado e amostra). Os melhores resultados foram obtidos utilizando o método sem incubação prévia, com a sensibilização da placa com 0,25µg/poço de anti-IgG de coelho, o anticorpo específico na diluição 1:250.000 e 0,06ng/poço de IGF-I biotinilado. O ensaio in house apresentou um limite inferior de detecção de 50ng/mL, uma correlação de 0,945 entre doses quando comparado a uma metodologia comercial. Os coeficientes de variação inter-ensaio de 12,94% (345,8ng/mL) para os controles alto e 20,71% (131,6ng/mL) para o baixo. Dessa forma, conclui-se que a metodologia imunoenzimática para quantificação de IGF-I total utilizando o sistema de amplificação biotina-estreptavidina peroxidase em um ensaio competitivo está estabelecida e apresenta-se como uma ferramenta útil para estudos que visem o monitoramento das concentrações de IGF-I.(AU)

This study aimed to standardize an in house competitive enzyme-linked immunosorbent assay (cELISA) to determine plasma concentrations of total insulin-like growth factor I (IGF-I) for the bovine specie using the amplification biotin-streptavidin peroxidase system. The IGF-I was extracted from insulin-like growth factor binding proteins (IGFBPs) using the acidified glycine buffer followed by the pH neutralization with sodium hydroxide. The microplates were coated with anti-rabbit IgG, thereafter the measurements were carried out using two approaches, one with a prior incubation of samples with the anti-h-IGF-I antibody and another without previous incubation (simultaneous addition of IGF-I and biotinylated sample). The best results were obtained using the method without the prior incubation, using the following combination of reagents: microplates were coated with 0.25µg/well of anti-rabbit IgG, the specific antibody at a dilution of 1:250,000 and 0.06ng/well of biotinylated IGF-I. The in house methodology showed sensitivity of 50ng/ml, a correlation between doses of 0.945 when compared to a commercial method. In addition, after 33 assays (quantification of 1114 samples) the proposed methodology presented a good precision, with inter-assay variation coefficients of 12.94% and 20.71% for the high and low controls, respectively. Finally, we concluded that ELISA method for the quantification of total IGF-I using the system biotin-streptavidin-peroxidase amplification in a competitive assay is established and is presented as a useful tool for studies aimed at monitoring the IGF-I concentrations.(AU)

Citotoxicity of Fipronil on Hepatocytes Isolated from Rat and Effects of Its Biotransformation

ABSTRACT The aim of this study was to characterize the mechanism of toxicity of fipronil on hepatocytes isolated from the rat and the effect of its biotransformation on the toxicological potential. The toxicity of fipronil was assessed by monitoring the oxygen consumption and mitochondrial membrane potential, intracellular ATP concentration, Ca2+ homeostasis and cell viability. The cell viability was evaluated by trypan blue exclusion in hepatocytes that were isolated from the normal rats and by the release of the enzymes alanine transaminase and aspartate transaminase in hepatocytes that were isolated from the normal rats or proadifen-pretreated rats. Fipronil reduced mitochondrial respiration in the cells that were energized with glutamate plus malate in a dose-dependent manner and dissipated the mitochondrial membrane potential that was accompanied by a reduction in ATP concentration and a disruption of intracellular Ca2+ homeostasis. The cell viability was affected by fipronil with higher potency in hepatocytes that were isolated from the normal rats, which indicated that the metabolism of this insecticide increased its toxicological potential. The results of this study indicated that the toxicity of fipronil to the hepatocytes was related to the inhibition of mitochondrial activity, which led to decreased ATP synthesis and a consequent alteration in intracellular Ca2+ homeostasis and ultimately resulted in cell death.

Mecanismos da intoxicação do fígado de rato causada pelo gossipol / Mechanisms of the intoxication of rat liver caused by gossypol

O fígado desempenha uma função central no metabolismo devido à sua interposição entre o trato digestivo e a circulação geral do organismo. Ele é também o principal órgão envolvido na biotransformação de substâncias exógenas (xenobióticos), com capacidade de converter compostos hidrofóbicos em hidrossolúveis, mais facilmente eliminados pelo organismo. O gossipol é uma substância fenólica tóxica presente na semente de algodão (Gossypium sp). Com o objetivo de estudar os mecanismos envolvidos na hepatotoxicidade do gossipol avaliou-se os seus efeitos no sistema antioxidante do fígado de ratos no que diz respeito ao estresse oxidativo e aspectos histopatológicos. Foram utilizados ratos machos da linhagem Wistar, separados em dois grupos, sendo que um recebeu óleo de canola (veículo, grupo Controle) e o outro recebeu gossipol na dosagem de 40 mg/kg de peso vivo do animal por 15 dias (grupo Tratado). O tratamento com gossipol promoveu alterações na atividade sérica das enzimas marcadoras de dano hepático e um significativo estresse oxidativo caracterizado pela diminuição nos níveis da glutationa reduzida (GSH) e consequente aumento da glutationa oxidada (GSSG), incluindo, ainda, danos à membrana plasmática e de organelas demonstrados pela peroxidação lipídica. O resultado da avaliação histopatológica demonstrou degeneração dos hepatócitos.

The liver plays a central role in metabolism due to its interposition between the digestive tract and the general circulation of the organism. It is also the main organ involved in biotransformation of exogenous substances (xenobiotics), with ability to convert hydrophobic compounds in water-soluble, more easily eliminated by the body. Gossypol is a toxic phenolic substance present in cotton seed (Gossypium sp.). Aiming to study the mechanisms involved in the hepatotoxicity of gossypol we evaluate its effects on the antioxidant system of rat liver performing an experiment that investigated the oxidative stress and the histopathological alterations. In this study, we used Wistar rats, divided into two groups, one that received canola oil (vehicle, Control group) and another that received gossypol at a dose of 40mg/kg body weight of the animal for 15 days (Treated group). The treatment with gossypol caused alterations in the activity of seric enzymes that indicate hepatic injury and a significant oxidative stress characterized by a decrease of reduced glutathione (GSH) levels and a consequent increase in oxidized glutathione (GSSG), including further damage to the plasma membrane and organelles showed by lipid peroxidation. The result of histopathological evaluation showed degeneration of the hepatocytes.

Dehydromonocrotaline induces cyclosporine A-insensitive mitochondrial permeability transition/cytochrome c release.

Monocrotaline (MCT) is a pyrrolizidine alkaloid present in plants of the genus Crotalaria that causes cytotoxicity and genotoxicity in animals and humans. It is well established that the toxicity of MCT results from its hepatic bioactivation to dehydromonocrotaline (DHM), an alkylating agent, but the exact mechanism of action remains unknown. In a previous study, we demonstrated DHM's inhibition of mitochondrial NADH-dehydrogenase activity at micromolar concentrations, which is an effect associated with a significant reduction in ATP synthesis. As a follow-up study, we have evaluated the ability of DHM to induce mitochondrial permeability transition (MPT) and its associated processes in isolated rat liver mitochondria. In the presence of 10 microM Ca(2+), DHM (50-250 microM) elicited MPT in a concentration-dependent, but cyclosporine A-independent manner, as assessed by mitochondrial swelling, which is associated with mitochondrial Ca(2+) efflux and cytochrome c release. DHM (50-250 microM) did not cause hydrogen peroxide accumulation but did deplete endogenous glutathione and NAD(P)H, while oxidizing protein thiol groups. These results potentially indicate the involvement of mitochondria, via apoptosis, in the well-documented cytotoxicity of monocrotaline.

Effects of monocrotaline on energy metabolism in the rat liver.

Monocrotaline (MCT) is a pyrrolizidine alkaloid present in the plants of the Crotalaria species that causes cytotoxicity and genotoxicity in animals and humans, and it is hepatically metabolized to the alkylating agent dehydromonocrotaline by cytochrome P-450. The exact cellular and molecular mechanisms of MCT-induced tissue injury remain unclear. We previously demonstrated that dehydromonocrotaline, but not monocrotaline, inhibits the activity of NADH-dehydrogenase at micromolar concentrations in isolated liver mitochondria, an effect associated with significantly reduced ATP synthesis. Impairment of energy metabolism is expected to lead to several alterations in cell metabolism. In this work, the action of different concentrations of monocrotaline (250, 500, and 750microM) on energy metabolism-linked parameters was investigated in isolated perfused rat livers. In the fed state, monocrotaline increased glycogenolysis and glycolysis, whereas in the livers of fasted rats, it decreased gluconeogenesis and urea synthesis from l-alanine. These metabolic alterations were only found in livers of phenobarbital-treated rats, indicating that active metabolites including dehydromonocrotaline were responsible for the observed activity. Our findings indicate that hepatic metabolic changes may be implicated, partly at least, in the hepatotoxicity of monocrotaline in animals and humans.