Whey protein stimulated the proliferation and differentiation of osteoblastic MC3T3-E1 cells

We examined the effects of whey protein on osteoblastic MC3T3-E1 cells. This protein caused dose-dependent increases in [3H]thymidine incorporation and DNA content in the cells. It also increased the total protein and hydroxyproline contents in the cells. These activities were heat resistant when the protein was heated at 75 degrees C to 90 degrees C for 10 min. Heat-treated whey protein was first fractionated on a Mono S column, and the active fraction (basic protein fraction) was then applied to Superose 12. The molecular weights of the active components were approximately 10,000 and 14,000 Da, as determined with gel filtration. The inner solution of an everted gut-sac incubated in a solution of intact BP (basic protein), pepsin-digested BP or pepsin/pancreatin-digested BP also stimulated the [3H]thymidine incorporation. Thus these active components can possibly permeate or be absorbed by the intestines. We propose the possibility that the active component in the whey protein plays an important role in bone formation by activating osteoblasts.