The effect of alkalosis on the glucose-mediated insulin release by the rat.

Bicarbonate loaded (alkalotic) rats had reduced plasma phosphate and ionized Ca concentrations and increased urinary cAMP excretion, phosphate clearance and pancreatic tissue uptake of extracellular calcium, all known effects of increased parathyroid hormone (PTH) secretion. Total insulin secretion after glucose challenge was enhanced in these animals. The response of alkalotic thyroparathyroidectomized rats, on the other hand, suggested exhaustion or inhibition of insulin secretion. The hypothesis is advanced that PTH, enhancing the permeability to calcium of the beta-cell membrane, compensated the effect of decreased calcium concentration in the extracellular fluid caused by alkalosis. PTH appears instrumental for homeostatic adjustments of insulin secretion.