Multi-origins of milk serum albumin in the lactating goat.
L-[U-14C]Leucine was infused into the right-hand mammary glands of lactating goats. Milk from both glands of the animals was sampled at intervals for 36 h. After 3 h the specific activity of milk serum albumin from the infused glands was more than six times that from the non-infused glands. The specific activity of milk serum albumin was considerably lower than that of alpha-lactalbumin or beta-lactoglobulin which are exclusively synthesized by mammary secretory cells. Following the intravenous injection of 125I-labeled serum albumin, maximum specific activity of this protein appeared in milk in 12 h. The specific activity of serum albumin in milk attained no more than 45% of the specific activity of the serum albumin in blood. It is concluded that milk serum albumin has multiple origins and that a portion of it, at least (10-20%), is made in the mammary gland.
D000818:Animals; D005260:Female; D006041:Goats; D007700:Kinetics; D007774:Lactation; D007930:Leucine / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000032:analysis*; D008894:Milk Proteins / Q000096:biosynthesis; D011247:Pregnancy; D012709:Serum Albumin / Q000096:biosynthesis*
D008894:Milk Proteins; D012709:Serum Albumin; D007930:Leucine