Ultramicrofluorimetric determination of calcium in plasma

Measurement of Total, Ultrafilterable and Ionised Serum Calcium

The development and assessment of methods for measurement of total, ultrafilterable and ionised serum calcium is given. An existing fluorimetric technique for total calcium has been automated and modified for routine use. A device for rapidly preparing serum ultrafiltrates has been developed and an electrometric method for ionised calcium measurement assessed. Values in normal subjects are given for all three fractions and compared with the findings of other workers.

Continuous flow techniques for the determination of serum calcium and the simultaneous determination of calcium and inorganic phosphate in serum and urine

The fluorometric method of Fingerhut et al. (1969) for the determination of serum calcium has been modified to approximately treble the sensitivity. Using only 120 μl of sample a method has been developed for the simultaneous determination of calcium and inorganic phosphate in serum and urine, the phosphate being measured by complexing phosphomolybdate with methyl green, a method developed by Van Belle (1970). Only a single dialysis stage is required, and reagents and sample can be delivered using an AutoAnalyzer Pump I. The techniques correlate well with other methods. Accuracy and precision data are presented.

Weight gain and chemical changes in low birthweight infants after change from human milk to modified cow's milk

Weight gain and some biochemical changes were observed in 7 preterm infants of low birthweight when their diet was abruptly changed from one of human milk to a modified cow's milk formula. There was a fall in the serum calcium and a rise in the inorganic phosphate levels in the week after the changeover. Serum sodium was raised after two days, with a fall occurring over the following 5 days. Blood urea rose throughout the 7-day period. Accompanying these biochemical changes there was an acceleration in weight gain, and in 5 infants this was associated with peripheral oedema. In the second week after the changeover there was a deceleration in weight gain accompanied by loss of the oedema. Immaturity of certain homeostatic mechanisms required to cope with the higher protein and electrolyte content of the modified cow's milk accounts for these observations. A more gradual dietary changeover, therefore, seems advisable.

Plasma calcium fractions and the protein-binding of calcium in normal subjects and in patients with hypercalcaemia and hypocalcaemia

A study is reported of the estimation of plasma calcium fractions and the calcium-binding affinity of plasma proteins in a total sample of 59 people, which included 29 normal subjects and 30 patients with either hypercalcaemia or hypocalcaemia. It was demonstrated that when the sample was considered as a whole there was a significant correlation between the total plasma calcium concentration and the ultrafiltrable, ionized, and protein-bound calcium fractions and between the ultrafiltrable and ionized fractions. We have also demonstrated that in patients with either hypercalcaemia or hypocalcaemia, including acidotic uraemics, the calcium-binding affinity of the plasma proteins did not differ significantly from that in normal subjects. A significant correlation was also found between the total plasma calcium concentration and the ultrafiltrable, ionized and protein-bound calcium fractions when the normal subjects and the groups of patients with hypercalcaemia and hypocalcaemia due to chronic renal failure were considered as separate groups. The group of patients with hypercalcaemia included patients both with hyperparathyroidism and with hypercalcaemia due to other causes.

Value of plasma chloride concentration and acid-base status in the differential diagnosis of hyperparathyroidism from other causes of hypercalcaemia

A study is reported of the estimation of plasma chloride concentration and acid-base status in the differentiation of primary hyperparathyroidism from all other causes of hypercalcaemia. In the two groups of patients studied, all of whom had hypercalcaemia, there was complete separation between the two groups on the basis of plasma chloride concentration and acid-base status. In 16 patients with primary hyperparathyroidism the increase in plasma chloride concentration and associated metabolic acidosis could have been accounted for by the known renal tubular effects of parathyroid hormone. In 13 patients with hypercalcaemia due to various other causes the decrease in plasma chloride concentration and associated metabolic alkalosis could be accounted for either by the known effects of an excess of calcium-ion on the renal tubules, or perhaps by suppression of endogenous parathyroid hormone secretion. In patients with hypercalcaemia and hypophosphataemia of ;pseudohyperparathyroidism' associated with non-endocrine tumours it is postulated that the low plasma chloride concentrations and metabolic alkalosis found in these patients were due either to a differing biological activity of the parathyroid-hormone-like polypeptide secreted by the tumour cells, or possibly to simultaneous secretion by these cells of an ACTH-like polypeptide.

A fluorimetric and enzymatic method for the estimation of serum total bile acids

The enzymatic technique using 3alpha-hydroxysteroid dehydrogenase for determining bile acids in blood has been modified by measuring the reduced nicotinamide adenine dinucleotide fluorimetrically. The increased sensitivity attained enables the concentration of total bile acids in serum to be estimated using 3 ml for normal subjects and 1 ml for jaundiced patients. The range of normal values in serum was found to be 0-4.7 mumol/litre for males and 1.0-8.2 mumol/litre for females.