STEROL-METABOLISM IN FETAL, NEWBORN, AND SUCKLED LAMBS AND THEIR RESPONSE TO CHOLESTEROL AFTER WEANING

Several aspects of cholesterol metabolism were studied in lambs at six stages of development. The first three stages involved fetal lambs with gestational ages (fertilization set at -150 days) of -73 days (early fetal), -42 days (midfetal), and -14 days (late fetal). The other groups comprised newborn (0 days), suckled (17 days), and weaned (105 days) lambs. The liver, kidney, spleen, and brain actively synthesized cholesterol at all stages of development, but hepatic synthesis in the suckled lambs was markedly suppressed compared with that in their newborn and weaned counterparts. Whereas intestinal sterol synthesis was very low in all the fetal lambs, the converse was true in the neonatal animals. The total cholesterol concentration in the liver, intestine, kidney, and spleen remained relatively constant at all stages of growth, whereas in brain tissue it increased throughout development. Plasma total and low-density-lipoprotein cholesterol levels were lowest in the late fetal lambs and highest in the suckled animals. The metabolic response of weaned lambs to a dietary cholesterol challenge was similar to that reported for various monogastric species.