Creatinine is an appropriate reference for urinary sulphatoxymelatonin of laboratory animals and humans

Abstract

In our studies on diurnal 6-sulphatoxymelatonin (aMT6s) rhythms in various species, we have sometimes obtained fluctuating patterns. In most of these, the volume of individual urine fractions was not accurately measured because of methodological problems. Here, we report a simple method to overcome these problems by using urinary creatinine to estimate urine volume. The benefit of this method is demonstrated in two representative examples of the diurnal aMT6s rhythms of rats, domestic pigs and humans. Because the human urine fractions were collected accurately, the qualitative pattern of the aMT6s rhythm was not altered by using urinary creatinine as a substitute for urine volume. The total creatinine excretion (urine volume x creatinine concentration) was constant within a small range and showed no diurnal rhythm. In rats and pigs, the highly variable aMT6s concentrations relative to urine volume throughout the 24-hr period were changed drastically by referring to creatinine. All aMT6s patterns became stable and qualitatively similar to those of the rest of the group. From these results it can be concluded that creatinine is an adequate substitute for urine volume and a beneficial parameter with which to overcome technical problems with urine collection from laboratory animals or unknown urine volumes in human studies.

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

“…The nature of the conjugation products of melatonin was reported over 40 yr ago in rats to be 6-sulphatoxymelatonin and 6-glucuronylmelatonin (20), and this was subsequently confirmed in humans (9,22,23,37). With the development of a RIA for 6-sulphatoxymelatonin (1), it has been possible to monitor the excretion of 6-sulphatoxymelatonin into the urine of humans (10), rats (17), Djungarian hamsters (21), minks (26), and pigs (19). In all cases, the excretion rate of 6-sulphatoxymelatonin is rhythmic and can be used as an index of pineal gland rhythmicity (10).…”

Effects of Different Light Intensities in the Morning on Dim Light Melatonin Onset

“…To adjust for variation in the dilution of urine, creatinine-adjusted aMT6s concentrations were used (Klante et al, 1997;Graham et al, 1998). For the analysis of aMT6s and creatinine, we used the 6-sulphatoxymelatonin ELISA kit (Buhlmann Laboratories) and the Urinary Creatinine Detection Kit (Luminos, Michigan, US), respectively.…”

GSM modulated radiofrequency radiation does not affect 6‐sulfatoxymelatonin excretion of rats

“…The measurement of 6SM excretion into urine provides a valid and quantitative index of melatonin secretion of pineal gland [Stieglitz et al, 1995]. In long term studies, creatinine is an appropriate reference for urinary 6SM of rats [Klante et al, 1997].…”