A Long-Term Effect of Insulin on Collagen Synthesis by Newborn Rat Bone in Vitro

In order to further characterize the effects of insulin on collagen synthesis by newborn rat bone in vitro, the time course of insulin action on incorporation of proline as proline and as hydroxyproline has been studied. In an incubation system, there was no stimulation by insulin at either three or six hours. In a flowing organ culture system, no significant effect of insulin could be observed at six hours; a small but significant effect on incorporation of proline as proline (but not as hydroxyproline) was seen at eighteen hours; and a highly significant effect on the incorporation of proline as both proline and hydroxyproline was observed at forty-two hours. Possible explanations for the delayed onset of insulin activity are discussed and the pattern contrasted with the rapid effect of insulin on collagen synthesis by skin of newborn rats.