EFFECT OF RELATIVELY LONG-TERM HYPOMAGNESEMIA ON THE CHONDRO-OSSEOUS FEATURES OF THE RAT VERTEBRAE

Cartilage and bone in the lumbar vertebrae of magnesium-deficient (LoM g) rats were studied after 4 and 8 weeks of Mg restriction. LoMg anima ls receiving 0.03% Mg intake had significantly reduced serum Mg levels compared to controls (receiving 0.2% Mg) at bath 4 weeks [0.66+/-0.06 mg% mean +/- SE (n = 10)] and 8 weeks [0.74+/-0.02 mg% (n = 3)] of st udy. Mean width of the vertebral growth plate was significantly decrea sed in LoMg animals at 4 weeks [54.7+/-3.5 mu m (n = 9) vs. control 68 .0+/-3.0 mu m (n = 6)] and 8 weeks [39.5+/-2.8 mu m (n = 3) vs. contro l 57.5+/-3.6 mu m (n = 3)]. The mean number of cells/cartilage column in the growth plate was also less at 4 weeks [5.8+/-0.18 (n = 5) vs. c ontrol 7.2+/-0.19 (n = 5)] and 8 weeks [4.9+/-0.19 (n = 3) vs. control 6.2+/-0.08 (n = 3)]. A significant proportion of LoMg animals possess ed decreased pericolumnar diastase-PAS reactivity at 4 and 8 weeks of study; this indicates a decrease in cartilage glycoprotein content dur ing Mg deficiency. Quantitative histomorphometric analysis determined that vertebral trabecular bone possessed significantly decreased perce ntage of osteoid surface (2.49+/-0.54 vs. control 6.98+/-2.8) and sign ificantly decreased percentage of osteoid area (0.18+/-0.05 vs. contro l 0.82+/-0.38) after 4 weeks of Mg deficiency. These findings document significant alterations in both bone and cartilage histologic feature s following relatively long-term Mg deficiency.