Qualification and quantification of seventeen natural steroids in plasma by GC-Q-MS and GC-IT-MS/MS.

Studying the plasma steroid profile offers information about the possible existence of endocrinological alterations. This study describes the development and validation of gas chromatographic-mass spectrometric and gas tandem mass spectrometric methods for the simultaneous identification of 17 steroid hormones in human plasma using five different solvents. The n-hexane/ethyl acetate solvent mixture, in a proportion of 70/30 (v/v) provided the best results. The extracts were derivatized with N-methyl-N-trimethylsilyl-trifluoroacetamide. The obtained limits of detection were below 1 ng/mL in the majority of the studied steroids and the limits of quantification were below 5 ng/mL; the method obtained good linearity, reproducibility, repeatability, accuracy and recoveries above 95% in most cases.

Determination of natural corticosteroids in urine samples from sportsmen.

A method for the determination of natural corticosteroids (cortisone, cortisol, 5beta-dihydrocortisone, 5beta-dihydrocortisol, tetrahydrocortisone and tetrahydrocortisol) found in the urine of sportsmen, was developed using a capillary gas chromatography-mass spectrometry ion trap system. 17alpha-Methyltestosterone was used as an internal standard. The different corticosteroids were determined from the peak area ratios of the [M]; [M-90] and [M-90-90] fragment ions of their methoxime-trimethylsiyl derivatives. Sensitivity (15 ppb), specificity, accuracy (96%) and reproducibility (RSD=4-10%) of the method were demonstrated to be satisfactory for measuring the urinary concentrations of the selected natural corticosteroids.

Determination of nandrolone and metabolites in urine samples from sedentary persons and sportsmen.

Metabolites of nandrolone were determined in the urine of several sportsmen, sedentary and post-menopausal women by capillary gas chromatography-mass spectrometry quadrupole (GC-MS) and capillary gas chromatography mass-mass spectrometry ion trap (GC-MS-MS) methods. The method employed was GC-EI-MS with 17alpha-methyltestosterone as internal standard with ethyl ether extraction prior to selected ion monitoring of the bis(trimethylsilyl) ethers at ion masses m/z 405 and 420 for the nandrolone metabolites, and 418 and 403 for nandrolone derivative. Recovery for nandrolone, 19-norandrosterone (19-NA) and 19-noretiocholanolone (19-NE) was 97.20, 94.17 and 95.54%, respectively. Detection limits for nandrolone, 19-NA and 19-NE were 0.03, 0.01 and 0.06 ng/ml. Metabolites of nandrolone (19-NA and 19-NE) were found in 12.5% (n = 40) of sportsmen and 40% (n = 10) of post-menopausal women.

[Nutrient absorption rate from the peritoneal cavity in rats]. / Velocidad de absorción de nutrientes desde la cavidad peritoneal de ratas.

A study has been done of the absorption/elimination kinetics of nutritive substances such as glucose, amino acids and fats from the peritoneal cavity. For this purpose, 48 male Wistar rats were administered an intravenous or intraperitoneal "bolus" of 2 microCi of L-glucose-C14/250 g of body weight, 3 microCi of D-alanine-L-C14/250 g and 0.4 g of Intralipid/250 g body weight. A two-compartment pharmacokinetic model was applied to determine the absorption, elimination and distribution constants among the different body compartments of each of these substrates, as well as the absorption and elimination halflife. When the areas under the curves were compared following intravenous and intraperitoneal infusion, the total physiological availability or fraction of dose absorbed over a given period of time were calculated. A higher absorption and elimination constant for glucose and amino acids as compared to fats was found. Higher than 90% absorption for all substrates was found, but since in the case of fats the elimination constant is lower and longer the elimination halflife, we must be cautious regarding its infusion rate.