Calcium secretion in the isolated perfused canine pancreas
| Autor: | H. Rohrmoser, H. Teufel, P. Stock, M. M. Forell |
|---|---|
| Rok vydání: | 1979 |
| Předmět: |
medicine.medical_specialty
Secretory Rate chemistry.chemical_element Calcium Biology In Vitro Techniques Secretin Dogs Pancreatic Juice Internal medicine Calcium-binding protein medicine Extracellular Animals Pancreas Calcium-Binding Proteins General Medicine Calcium ATPase Perfusion Kinetics Secretory protein Endocrinology chemistry Pancreatic juice |
| Zdroj: | Research in experimental medicine. Zeitschrift fur die gesamte experimentelle Medizin einschliesslich experimenteller Chirurgie. 176(1) |
| ISSN: | 0300-9130 |
| Popis: | The quantitative relation of calcium and protein secretion was studied on the isolated perfused canine pancreas at different secretory states of hydrokinetic and ecbolic stimulation and various extracellular Ca++-concentrations. 1. Calcium and protein secretion are correlated at both ecbolic and hydrokinetic stimulation as well as by biological or synthetic secretion. 2. Enzyme-associated calcium was estimated at 35 nmol/mg protein and did not vary under differing stimulatory and secretory conditions. 3. During variable concentrations of synthetic secretin basal protein and calcium concentrations in the pancreatic juice show a hyperbolic relationship to the respective rates of fluid secretion. At flow rates beyond 3 ml/5 min the calcium concentrations asymptotically tend to 0.46 mEq/l while protein concentrations nearly decrease to zero. Moreover, the y-intercept of the regressionline correlating the calcium and protein concentrations gives with 0.48 mEq/l Ca++ additional evidence of the existence and magnitude of an enzyme-independent calcium fraction, which seems to remain constant over the whole range of secretory rates. 4. The omission of perfusate calcium does not abolish the calcium-protein correlation either at hydrokinetic or at ecbolic stimulation, but diminishes the enzyme-independent calcium fraction. 5. Enhancing perfusate Ca++-concentrations augments calcium output byt fails in stimulating enzyme secretion. It is concluded that at exclusively hydrokinetic stimulation basal secreted protein with a definite amount of chelated calcium is diluted by variable rates of pancreatic juice containing enzyme independent Ca++ at a constant concentration. During different secretory states of hydrokinetic or ecbolic stimulation the respective proportions of enzyme associated and independent calcium vary, and thus determine changes in the calcium-protein ratios. Extracellular calcium can only influence the non-protein-bound calcium fraction of the pancreatic juice presumably by diffusion from the extracellular fluid through the ductal epithelium rather than by an active secretory mechanism. |
| Databáze: | OpenAIRE |
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