Effect of calcitriol and trifluoperazine on glucose stimulated B cell function in healthy humans

The authors investigated the effects of pharmacological doses of calcitriol (1,25(OH)2-vitamin D3) and trifluoperazine on metabolic and hormonal indicators of glycoregulation in the course of the intravenous glucose tolerance test (IVGTT) in healthy subjects. Calcitriol administered by the oral route for four days, 3 micrograms/d, did not alter the blood sugar and plasma IRI levels at rest nor glucose stimulated values throughout the IVGTT. The slight increase of the glucose assimilation coefficient was not significant, as compared with values of the control test (Kg = (3.9 +/- 0.5) x 10(-2) [min-1] vs. Kg = (3.4 +/- 0.3) x 10(-2) [min-1], respectively). C-peptide plasma levels after calcitriol were slightly higher, significantly during the 14th minute following glucose administration (p less than 0.05), while the two-peak shape of the curve was preserved. Trifluoperazine administered by the oral route for seven days, 10 mg/d, did not significantly affect the blood sugar, IRI and C-peptide values at rest nor glucose induced values throughout the IVGTT nor values of glucose assimilation (Kg = (3.0 +/- 0.4) x 10(-2) [min-1] vs. Kg = (3.4 +/- 0.3) x 10(-2) [min-1] in the control test). In conclusion, neither calcitriol nor trifluoperazine treatment leads to clinically significant alteration of glycoregulation.