Relationship between bone resorption and lysosomal enzyme release as demonstrated by the effect of 1 alpha-hydroxy-vitamin D-3 in an organ culture system.

The effect of 1 alpha-hydroxy-vitamin D-3 on the release of calcium (40Ca, 45Ca), inorganic phosphate and lysosomal enzymes, on glucose consumption and lactate production was studied in a bone organ culture system using half calvaria from 6--7-day-old mice. 1 alpha-Hydroxy-vitamin D-3 stimulated the mobilization of minerals and increased the release of beta-glucuronidase, beta-N-acetylglucosaminidase and acid phosphatase, while no effect on the release of lactate dehydrogenase was seen. 1 alpha-Hydroxy-vitamin D-3 also caused a significant increase in the total activities of acid phosphatase in the bones after culture, indicating increased enzyme synthesis. The stimulatory effect on the release of Pi and beta-glucuronidase was also obtained after a temporary exposure to 1 alpha-hydroxy-vitamin D-3. The stimulation by 1 alpha-hydroxy-vitamin D-3 on the release of Ca2+, Pi and beta-glucuronidase was suppressed by a protein synthesis inhibitor, cycloheximide. No effect by 1 alpha-hydroxy-vitamin D-3 on glucose consumption and lactate production was registered, suggesting that increased mineral mobilization does not require increased lactate production. It is concluded that although the data in the present paper do not prove a cause-and-effect relationship between lysosomal enzyme release and bone resorption, they give further support to the concept that the processes are intimately associated.