In Vitro Studies Indicate Intravenous Lipid Emulsion Acts as Lipid Sink in Verapamil Poisoning.

Intravenous lipid emulsion (ILE), a component of parenteral nutrition, consists of a fat emulsion of soy bean oil, egg phospholipids, and glycerin. Case reports suggest that ILE may reverse hypotension caused by acute poisoning with lipophilic drugs such as verapamil, but the mechanism remains unclear. The methods used are the following: (1) measurement of ILE concentration in serum samples from a patient with verapamil poisoning treated with ILE, (2) measurement of free verapamil concentrations in human serum mixed in vitro with increasing concentrations of ILE, and (3) measurement of murine ventricular cardiomyocyte L-type Ca(2+) currents, intracellular Ca(2+), and contractility in response to verapamil and/or ILE.

Resolution of an apparent hook effect in Roche partner DRI oxycodone immunoassay.

A presumed hook effect in the semiquantitative DRI Oxycodone immunoassay, OXY3S (Cobas Integra, Roche Diagnostics), was investigated in 14 urine samples with gas chromatography/mass spectrometry (GC-MS) >10,000 ng/mL but OXY3S <1,000 ng/mL. These samples included the index case, a false-negative OXY3S result with >75,000 ng/mL oxycodone + oxymorphone by GC-MS confirmation. Patient samples needed 2- to 16-fold dilution to obtain the correct OXY3S response.

Primary prevention of pediatric lead exposure requires new approaches to transfusion screening.

Objective: To facilitate further assessment of transfusion-associated lead exposure by designing a procedure to test packed red blood cells (pRBCs) prepared for transfusion.

Study Design: The relationship between pRBCs and whole blood lead concentration was investigated in 27 samples using a modified clinical assay. Lead concentrations were measured in 100 pRBC units.

Estrogen metabolism and exposure in a genotypic-phenotypic model for breast cancer risk prediction.

Background: Current models of breast cancer risk prediction do not directly reflect mammary estrogen metabolism or genetic variability in exposure to carcinogenic estrogen metabolites.

Methods: We developed a model that simulates the kinetic effect of genetic variants of the enzymes CYP1A1, CYP1B1, and COMT on the production of the main carcinogenic estrogen metabolite, 4-hydroxyestradiol (4-OHE(2)), expressed as area under the curve metric (4-OHE(2)-AUC). The model also incorporates phenotypic factors (age, body mass index, hormone replacement therapy, oral contraceptives, and family history), which plausibly influence estrogen metabolism and the production of 4-OHE(2).

Estrogen metabolism and breast cancer: a risk model.

Oxidative metabolites of estrogens have been implicated in the development of breast cancer, yet relatively little is known about the metabolism of estrogens in the normal breast. We developed an experimental in vitro model of mammary estrogen metabolism in which we combined purified, recombinant phase I enzymes CYP1A1 and CYP1B1 with the phase II enzymes COMT and GSTP1 to determine how 17beta-estradiol (E(2)) is metabolized. We employed both gas and liquid chromatography with mass spectrometry to measure the parent hormone E(2) as well as eight metabolites, that is, the catechol estrogens, methoxyestrogens, and estrogen-GSH conjugates.

Effects of a selective serotonin reuptake inhibitor, fluoxetine, on counterregulatory responses to hypoglycemia in healthy individuals.

Objective: Hypoglycemia commonly occurs in intensively-treated diabetic patients. Repeated hypoglycemia blunts counterregulatory responses, thereby increasing the risk for further hypoglycemic events. Currently, physiologic approaches to augment counterregulatory responses to hypoglycemia have not been established.

Cytochrome P450 1B1-mediated estrogen metabolism results in estrogen-deoxyribonucleoside adduct formation.

The oxidative metabolism of estrogens has been implicated in the development of breast cancer; yet, relatively little is known about the mechanism by which estrogens cause DNA damage and thereby initiate mammary carcinogenesis. To determine how the metabolism of the parent hormone 17beta-estradiol (E2) leads to the formation of DNA adducts, we used the recombinant, purified phase I enzyme, cytochrome P450 1B1 (CYP1B1), which is expressed in breast tissue, to oxidize E2 in the presence of 2'-deoxyguanosine or 2'-deoxyadenosine. We used both gas and liquid chromatography with tandem mass spectrometry to measure E2, the 2- and 4-catechol estrogens (2-OHE2, 4-OHE2), and the depurinating adducts 4-OHE(2)-1(alpha,beta)-N7-guanine (4-OHE2-N7-Gua) and 4-OHE(2)-1(alpha,beta)-N3-adenine (4-OHE2-N3-Ade).

Estrogens, enzyme variants, and breast cancer: a risk model.

Oxidative metabolites of estrogens have been implicated in the development of breast cancer, yet relatively little is known about the metabolism of estrogens in the normal breast. We developed a mathematical model of mammary estrogen metabolism based on the conversion of 17beta-estradiol (E(2)) by the enzymes cytochrome P450 (CYP) 1A1 and CYP1B1, catechol-O-methyltransferase (COMT), and glutathione S-transferase P1 into eight metabolites [i.e.

Unmasked adult-onset urea cycle disorders in the critical care setting.

Most often, urea cycle disorders have been described as acute onset hyperammonemia in the newborn period; however, there is a growing awareness that urea cycle disorders can present at almost any age, frequently in the critical care setting. This article presents three cases of adult-onset hyperammonemia caused by inherited defects in nitrogen processing in the urea cycle, and reviews the diagnosis, management, and pathophysiology of adult-onset urea cycle disorders. Individuals who have milder molecular urea cycle defects can lead a relatively normal life until a severe environmental stress triggers a hyperammonemic crisis.

In vitro model of mammary estrogen metabolism: structural and kinetic differences between catechol estrogens 2- and 4-hydroxyestradiol.

Estrogens and their oxidative metabolites, the catechol estrogens, have been implicated in the development of breast cancer; yet, relatively little is known about estrogen metabolism in the breast. To determine how the parent hormone, 17 beta-estradiol (E(2)), is metabolized, we used recombinant, purified phase I enzymes, cytochrome P450 (CYP) 1A1 and 1B1, with the phase II enzymes catechol-O-methyltransferase (COMT) and glutathione S-transferase P1 (GSTP1), all of which are expressed in breast tissue. We employed both gas and liquid chromatography with mass spectrometry to measure E(2), the catechol estrogens 2-hydroxyestradiol (2-OHE(2)) and 4-hydroxyestradiol (4-OHE(2)), as well as methoxyestrogens and estrogen-GSH conjugates.

Sequential action of phase I and II enzymes cytochrome p450 1B1 and glutathione S-transferase P1 in mammary estrogen metabolism.

The Phase I enzyme cytochrome p450 1B1 (CYP1B1) has been postulated to play a key role in estrogen-induced mammary carcinogenesis by catalyzing the oxidative metabolism of 17beta-estradiol (E(2)) to catechol estrogens (2-OHE(2) and 4-OHE(2)) and highly reactive estrogen quinones (E(2)-2,3-Q and E(2)-3,4-Q). The potential of the quinones to induce mutagenic DNA lesions is expected to be decreased by their conjugation with glutathione (GSH) either nonenzymatically or catalyzed by glutathione S-transferase P1 (GSTP1), a Phase II enzyme. Because the interaction of the Phase I and Phase II enzymes is not well defined in this setting, we prepared recombinant purified CYP1B1 and GSTP1 to examine their individual and combined roles in the oxidative pathway and used gas and liquid chromatography/mass spectrometry to measure the parent hormone E(2), the catechol estrogens, and the GSH conjugates.

Methoxyestrogens exert feedback inhibition on cytochrome P450 1A1 and 1B1.

Cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1) catalyze the oxidative metabolism of 17 beta-estradiol (E2) to catechol estrogens (2-OHE2 and 4-OHE2) and estrogen quinones, which may lead to DNA damage. Catechol-O-methyltransferase catalyzes the methylation of catechol estrogens to methoxyestrogens (2-MeOE2, 2-OH-3-MeOE2, and 4-MeOE2), which simultaneously lowers the potential for DNA damage and increases the concentration of 2-MeOE2, an antiproliferative metabolite. In this study, we showed that CYP1A1 and CYP1B1 recognized as substrates both the parent hormone E2 and the methoxyestrogens.