Chromium-induced inhibition of insulin secretion from isolated Islets of Langerhans

Summary CrCl₃, 0.25, 0.5, 1.0, and 1.5 mmol/l inhibited glucose-induced insulin secretion in a reversible and dose dependent manner. Cr also inhibited basal secretion of insulin in the presence of 5.5 mmol/l glucose and insulin secretion stimulated by 50 mmol/l K⁺ or 15 mmol/l L-leucine. When 2 mmol/l theophylline was employed to potentiate the stimulatory effect of 16.5 mmol/l glucose, the inhibitory effect of 1.5 mmol/l Cr was reduced and that of 0.5 mmol/l Cr virtually abolished. A similar reduction in the inhibitory effect of Cr was observed when the medium calcium concentration was increased from 2.5 to 5, 7.5 and 12.5 mmol/l. Cr did not alter the conversion of ¹⁴C-glucose to ¹⁴CO₂ or ⁴⁵Ca uptake by isolated islets. It is concluded that the inhibitory effect of Cr on insulin secretion may be mediated through interference with an intracellular function of Ca⁺⁺ in the beta cell.