Development and validation of a high throughput direct radioimmunoassay for the quantitative determination of serum and plasma melatonin (N-acetyl-5-methoxytryptamine) in mice

Development and validation of a high-thr

Development and validation of a high-throughput double solid phase extraction–liquid chromatography–tandem mass spectrometry method for the determination of tetrodotoxin in human urine and plasma

✍ Bonnie Mei-Wah Fong; Sidney Tam; Sik-Hon Tsui; Kelvin Sze-Yin Leung 📂 Article 📅 2011 🏛 Elsevier Science 🌐 English ⚖ 673 KB

Development and validation of a high-thr

Development and validation of a high-throughput method for the quantitative analysis of felodipine in human plasma using high-performance liquid chromatography with mass/mass spectrometer and its application to a bioequivalence study in healthy male Korean subjects

✍ Soo-Hwan Kim, Hye Jung Lee 📂 Article 📅 2012 🏛 Springer Netherlands 🌐 English ⚖ 492 KB

Saliva and serum samples were collected

Saliva and serum samples were collected from eight healthy volunteers every two hours during a 26-hour period. Melatonin concentrations were measured by radioimmunoassay after chloroform extraction using radioiodinated melatonin as a tracer. Five of the subjects had high serum melatonin levels at night (peak levels higher than 75 pg/ml); in three subjects the highest serum melatonin concentration was 20-40 pg/ml. All subjects had low levels (P <0.001, was obtained for all detectable value pairs (n= 73). The regression and correlation coefficients were almost equal for the peak values of melatonin and during the rising and descending phases of the secretion patterns. However, no significant correlation was found between low daytime salivary and serum concentrations when calculated separately. In the five high-secretors the melatonin levels in saliva reflected reliably the changes in serum, but in the three low-secretors the correlation between salivary and serum melatonin was not significant. The proportion of melatonin found in saliva decreased with increasing serum melatonin levels. Circadian rhythm parameters were estimated by single cosinor analysis. The acrophases did not differ significantly within a subject in the concomitant measurements of serum and salivary melatonin. The measurements of salivary melatonin levels seem valid for studies on melatonin rhythms, but the melatonin concentrations measured in saliva do not always consistently reflect the absolute concentrations in blood.

✍ Maija-Liisa Laakso; Tarja Porkka-Heiskanen; Aino Alila; Dag Stenberg; Gunnar Joh 📂 Article 📅 1990 🏛 John Wiley and Sons 🌐 English ⚖ 622 KB