The acidification response of normal subjects to ammonium chloride using a 3-day loading test.

The acidification response to NH4 Cl loading (0.1 g/kg bw/day) was tested in 16 normal healthy subjects in the basal fasting state on Day 4, the subjects having taken the salt daily for the 3 previous days. The response was measured in terms of blood pH and in urine, creatinine, phosphate, pH, titratable acidity, ammonium, net acidity and creatinine clearance. To minimise inter-subject variation the urine values were adjusted to a standard body surface area of 1.73 m2. A normal range for the blood pH of the mean value +/- 2 SD, encompassed the observed range of values. However, to fit the observed range of acid-base values in urine into the 2 SD range required a logarithmic transformation of the data. Statistical analysis confirmed a significant correlation between blood [H+] net acid secretion, urine titratable acidity and ammonium. Urine net acid secretion was positively correlated with urinary phosphate, titratable acidity and ammonium.

Sub-hourly variations in salivary estriol concentrations in the last trimester of pregnancy.

Sub-hourly variations in salivary estriol were measured in women in the last trimester of pregnancy. The mean and variation of salivary estriol concentrations in specimens collected at 5-min intervals for 30 min were greater on awakening in the morning (when subjects were recumbent and fasting) than in the afternoon. The differences in variation between morning and afternoon serial specimens were eliminated by the omission of the first two specimens collected in the morning. Significant differences between the mean concentrations obtained for morning and afternoon specimens were minimized by use of a recumbent posture for the afternoon specimen collection. The mean estriol concentration of four saliva samples collected at 5-min intervals for 15 min did not differ significantly from the concentration of saliva collected continuously over the subsequent 15 min. For routine estriol monitoring, therefore, samples should be collected over a 15-min period. This ought to be carried out at the same time of day, in the same posture on each occasion, but preferably not in the early morning.

Influence of sampling time on salivary oestriol concentrations in pregnant women.

Saliva specimens were collected at weekly intervals during the third trimester of 61 uncomplicated pregnancies. Oestriol concentrations, measured in samples collected in the early morning from fasting, recumbent subjects, were used to construct a provisional normal range. This proved to be higher than the corresponding normal range reported from another laboratory applying the same method to samples obtained at random from a different population of ambulant subjects. Interlaboratory variation in the assay of salivary oestriol was not sufficient to account for the difference in normal range. It is concluded that consideration should be given to the timing of sample collection if salivary oestriol concentration is to be monitored as a possible means of assessing fetoplacental function. A normal range for salivary oestriol concentration versus gestational age obtained from women sampled randomly may not be appropriate for monitoring patients with 'at-risk' pregnancies who are normally bed-rested.