Determination of calcium in microgram amounts of dried biological material by flameless atomic absorption spectrophotometry with special reference to the pancreatic islets

Flameless atomic absorption was used for direct measurements of calcium in microgram amounts of dried biological material. Sufficient analytical precision was reached with a commercial instrument complemented with a device allowing proper control of the heating of the graphite tube furnace. A comparison of different organs in the mouse revealed particularly high concentrations of calcium in the pancreatic islets. β cell-rich pancreatic islets from obob mice contained 60 mmol of calcium/kg dry weight. This value was reduced by 20 mmol during 120 min of washing in physiological saline. There was less calcium in the endocrine and exocrine parts of the directly excised pancreas than in samples incubated in Krebs-Ringer bicarbonate buffer. Islets microdissected from genetically diabetic mice were similar to those from nondiabetic controls with regard to the contents of both readily mobilizable and slowly exchangeable calcium.