Effects of 1.25-dihydroxycholecalciferol, parathormone and Ca2+ on the pancreatic B-cell sensitivity to alloxan.

The sensitivity to alloxan was investigated by blood and urine glucose determination and light and electron microscopic study of the endocrine pancreas in groups of mice differing from each other with respect to food ingestion and treatment before alloxan administration. Because of differences in occurrence of glucosuria, degree and duration of hyperglycemia, and severity of structural lesions, it was concluded that starvation increases the alloxan sensitivity and that pre-treatment with 1.25-dihydroxycholecalciferol (DHCC) or parathormone (PTH), but not with Ca2+, enhances the alloxan effect. The serum-calcium concentration determined 10 minutes after pre-treatment was significantly increased in the group given Ca2+, but not in the groups injected with DHCC or PTH. Starved mice injected with DHCC or PTH 10 minutes before alloxan administration exhibited a pronounced second hyperglycemia of long duration, and extensive, selective B-cell necrosis. Starvation and increased serum concentration of DHCC and PTH are believed, directly or indirectly, to induce B-cell alterations which increase the alloxan sensitivity.