The measurement of mercury excretion in urine

The determination of mercury in urine using cold atomic absorption spectrometry according to Gage and Warren is used after slight modification as standard method for the exposure test in persons exposed to its vapours in industry in Czechoslovakia. Within the concentration range between 100 and 600 nmol X l-1 of urine the relative standard deviation was lower than 4%. In workers exposed to mercury in the production of thermometers, fluctuation of urinary mercury concentration due to variations in diuresis could be greatly reduced by adjustment for endogenous creatinine. After the intake of 2.2 or 2.5 l of liquids the concentration of mercury in urine dropped considerably, but returned again to its initial value within 4 hours after fluid intake. The mercury half-life in the organism is estimated at about 30 days, but may be longer at mercury concentrations of 1 mumol X l-1. Contradictory to the original expectation, the Araki's coefficient b that is recommended for suppressing the effect of the volume of excreted urine on the concentration of urinary substances was found to be concentration-dependent: at 500 nmol X l-1 its value shifted towards 1 (0.85), at 100 nmol X l-1 towards zero (0.2-0.3). It is believed that mercury urinalysis data adjusted for endogenous creatinine are sufficiently reliable to be used for assessing the risk of human exposure to mercury.     

The kinetics of mutagen excretion in the urine of cigarette smokers

The excretion of mutagens in the urine of cigarette smokers was studied as a model for absorption and elimination of complex carcinogenic and mutagenic mixtures in humans. Urine was collected from an occasional smoker who smoked 1 cigarette (17 mg tar/cigarette) and from a heavy smoker (smokes approximately 20 cigarettes/day) who quit for 2 days and then resumed smoking. Urine samples were collected for 6 days, including a 2-day pre-smoking period for the occasional smoker and pre-abstention period for the heavy smoker, respectively. Mutagen excretion patterns were determined by extracting the mutagens in each urine sample with XAD-2 resin and testing the extract in a microsuspension modification of the Salmonella/microsome liquid-incubation assay using bacterial strain TA98 with metabolic activation. Peak mutagenic activity of the urine collected from the two smokers appeared 4-5 h after the beginning of smoking. Activity decreased to pre-smoking "baseline' levels in approximately 12 h for the occasional smoker, and the activity for the heavy smoker approached the occasional smoker's 'baseline' in approximately 18 h after the cessation of smoking. The mutagen excretion patterns of the occasional smoker after smoking a single cigarette suggests that, the mutagens, as detected by the Salmonella assay, are absorbed rapidly (3-5 h) and are eliminated from the body following first order kinetics. The excretion rate constant for the occasional smoker was approximately 0.1 h-1 and the half-life (T1/2) was approximately 7 h.     

Stimulation of ammonium ion excretion in the toad urinary bladder by an extract of human urine

It is well known that ammonium ion excretion is increased during metabolic acidosis in mammals. The purpose of this study was to determine whether we could isolate from human urine during metabolic acidosis a factor that would stimulate NH₄⁺ and/or H⁺ excretion in toad urinary bladder. Extracts of urine from six human subjects collected during NH₄Cl-induced acidosis were prepared. These extracts were tested for their effect on NH₄⁺ excretion in hemibladders mounted between plastic chambers. The extracts significantly increased NH₄⁺ excretion in the toad urinary bladder. We found no effect on H⁺ excretion by these extracts. This ammoniuretic activity was not present in the urine when the same individuals were in metabolic alkalosis. We conclude that during metabolic acidosis a humoral factor is present which stimulates the excretion of NH₄⁺. The factor could act as a permease in the bladder cell or as a stimulator of an NH₄⁺ transport system.     

Variability in rates of urine prostaglandin E excretion

Urine prostaglandin E excretion rates were determined by hepatic receptor assay in three groups of conscious animals. Although 24-hour urine collections gave reproducibly similar levels of prostaglandin E excretion rates, levels obtained with consecutive 20-minute urine collections were extremely variable despite no obvious changes in renal function. Since short urine collection periods are used frequently in physiologic studies, the significance of variations in prostaglandin excretion rates in these studies may have to be re-evaluated.