VITAMIN-D-3 INTOXICATION IN NAKED MOLE-RATS (HETEROCEPHALUS-GLABER) LEADS TO HYPERCALCEMIA AND INCREASED CALCIUM DEPOSITION IN TEETH WITH EVIDENCE OF ABNORMAL SKIN CALCIFICATION

Naked mole-rats have no access to obvious sources of vitamin D and the refore have an impoverished vitamin D status. In an investigation into the effects of vitamin D supplementation, inadvertently supraphysiolo gical doses of 130,000 times the normal dose of vitamin D were adminis tered. Within 5 days animals appeared lethargic, with reduced food int ake. All but one of the seven animals were killed and blood was collec ted. Plasma vitamin D metabolites 25(OH)D and 1,25(OH)(2)D and calcium were determined. Both vitamin D metabolite concentrations exceeded th e upper limits of sensitivity of the assays (>100 ng/ml 25(OH)D and >2 10 pg/ml 1,25(OH)(2)D). Active calcium uptake in the intestine was evi dent along with concomitant increases in calcium concentration in plas ma, bone, and teeth. The remaining animal survived, but showed scab-li ke formations in the skin around the lower jaw and along the nipple li ne. X-ray analyses revealed calcium deposition in these cornified regi ons, although there was no evidence of metastatic calcification in oth er tissues. Deposition of excess calcium in skin that is regularly slo ughed off and in teeth that are continuously worn down and replaced ma y reduce the Vitamin D-induced hypercalcaemia and thus alleviate the e ffects of vitamin D intoxication. (C) 1995 Academic Press, Inc.