Time course of closure of the ductus venosus in the newborn lamb.
The present study was designed to obtain quantitative data on the extent of portocaval shunting and the time course of closure of the ductus venosus in newborn lambs. Experiments were conducted on eight newborn lambs prepared with chronic portal catheters. The time course of the postnatal closure of the ductus venosus was determined by following the distribution of radiolabelled microspheres injected into the lamb's portal vein 24, 48, 96, and 168 hr after birth. The fraction of the portal blood flow which bypassed the liver was highly variable. In some animals, the ductus venosus was almost completely closed when the first microspheres were injected 24 hr after birth. In others, almost 40% of the portal blood flow bypassed the hepatic circulation at this time. On average, only 77% of the portal blood flow was directed to the liver in the 1-day lambs. In most cases, closure had occurred by 48 hr after birth, but some animals continued to divert a significant fraction of the portal flow away from the hepatic circulation.
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D008102:Liver Circulation; D011168:Portal System / Q000502:physiology*; D012756:Sheep