Effects of calcium deficiency and calcium supplementation on gastrectomy-induced osteopenia in the young male rat.

Background: Surgical removal of the stomach (gastrectomy, Gx) induces osteopenia. In this study we compared the osteopenic effect of Gx with that induced by calcium (Ca) deficiency. Methods: Young male rats were subjected to Gx and/or low Ca diet (-Ca). A group of Gx rats received standard diet + oral Ca supplementation (+ Ca). The rats were killed at various times after the operation/start of treatment (longest time 12 weeks). After 8 weeks on low Ca diet, the blood Ca 2 concentration was lowered slightly in both Sham-operated and Gx rats. The calvariac were subjected to transillumination analysis and quantitative histomorphometry. Also the tibiae were subjected to histomorphometry. Results: Transillumination of the calvariae revealed extensive bone loss in the rats that had been subjected to Gx and/or low Ca diet, Gx + Ca induced the same bone loss as Gx alone. These observations were later confirmed in quantitative terms by histomorphometry (Sham-Ca 56%, Gx 35%, Gx + Ca 32%, Gx - Ca 58% less bone area than in Sham). The osteopenia induced by Gx+ low Ca diet seemed more rapid in onset than that induced by Gx or low Ca diet alone. Tibiae from Gx rats and rats given a low Ca diet displayed a reduced trabecular bone volume (Sham-Ca 27%, remaining, Gx 36%, Gx + Ca 44%, Gx - Ca 1711) and reduced trabecular number (Sham-Ca 44% remaining, Gx 41%, Gx + Ca 56%, Gx - Ca 33%). The trabecular thickness was reduced in the Gx rats and Gx - Ca rats (Gx 78% remaining, Gx-Ca 63%) but not in Sham-operated rats receiving a low Ca-dict (95% remaining). Conclusion: Although the pattern of osteopenia was qualitatively quite similar in Gx rats and Ca-deficient rats, in quantitative terms the low Ca diet was more detrimental to bone than Gx. Ca deficiency induced a similar degree of osteopenia in both Sham and Gx rats. Ca supplementation failed to prevent the Gx-induced osteopenia.