CALCIUM AND VITAMIN-D ENRICHED DIET INCREASES AND PRESERVES AXIAL MINERAL-CONTENT IN AGING LABORATORY RATS

Osteoporosis is an age-related disorder characterized by a continuous decrease in absolute bone mass and an increased susceptibility to frac tures. Calcium (Ca) and vitamin D have been considered possible therap eutic agents for this disease and laboratory rodents proved a satisfac tory animal model for studies on pathogenesis and treatment of the con dition. The aim of the present study was to elucidate the effect of lo ng-term Ca and: vitamin D dietary supplementation on trabecular bone m ass and mineralization in aging laboratory rats. One and a half month old female Wistar rats (mean life-time 24 months, peak bone mass attai ned at the age of 12 months) were fed with a diet containing twice the concentration of both Ca and vitamin D as in usual rat chow. The pres ent longitudinal investigation of lumbar vertebrae showed no significa nt changes in the trabecular bone volume (BV/TV); yet in the senescent treated animals a reduction of 30% in the vertebral cortical area was observed as compared to a 68% reduction in controls. No significant c hanges in the vertebral protein content were noted but a significant i ncrease of skeletal Ca content was observed in treated animals compare d to controls. These differences persisted and even increased during t he time of senescence: vertebral bone mineral density (+58%), and vert ebral Ca content (+153%). Concomitantly we found a reduced enzymatic a ctivity of vertebral alkaline phosphatase (-45%) and of bone acid phos phatase (-14%). The marked reduction in the latter's ratio (-35%) migh t suggest a diminished rate of bone turnover in the Ca and vitamin D-t reated group.