Biochemical studies on the embryonic development of the mammalian inner ear in organ culture.

Adenylate cyclase activity and phospholipid labeling were compared during embryonic development of the mouse inner ear in vivo and in vitro. Inner ears were explanted on the 16th gestational day and cultured in vitro for 3-12 days. The gestation time in vivo is 21 days. During the 1st week in vitro there is very little growth of the inner ear with regard to total protein content. In contrast, the labyrinth increases its protein content threefold during the corresponding period of time in vivo. The activity of adenylate cyclase develops parallel in vivo and in vitro until the 19th gestational day whereafter the specific activity of the enzyme in vitro surpasses that of the enzyme in vivo three- to fivefold suggesting a lack of control mechanisms in organ culture. Phospholipids are labeled by 32P in an essentially similar quantitative relationship in vivo and vitro, while some quantitative differences exist. According to the present study the usefulness of the organ culture for the investigation of inner ear development appears limited to a culture period corresponding to an age prior to birth.