Effects of In Utero Phrenic Nerve Section on the Development of Collagen and Elastin in Lamb Lungs

Interference with fetal breathing movements is known to retard morphologic development of the lung and to reduce compliance. We hypothesized that the lower compliance might be in part due to effects on lung structural proteins. We studied the effects of phrenic nerve section in utero on lung compliance and on the lung contents of collagen, elastin, and DNA. At 110 to 112 days of gestation, one fetal lamb in each of 12 twin pregnancies had either both phrenic nerves cut (PX) or a sham operation (S). The other twin was left unoperated (Upx, Us) as a control. They were killed 14 to 22 days later, and the concentrations in lung parenchyma of collagen (as hydroxyproline HPro), elastin, and DNA were measured, together with lung compliance and dry and wet weight. Paired comparisons were made (PX versus Upx and S versus Us). Both operated groups (PX, S) had smaller lungs with lower water content than did their unoperated twins. Absolute static compliance in PX was reduced, but compliance relative to lung weight w...