Expression of Albumin in Nonhepatic Tissues and its Synthesis by the Bovine Mammary Gland

Abstract

Albumin is a well-characterized product of the liver. In the present study, objectives were to determine if the albumin gene is also expressed in various nonhepatic tissues in the bovine; whether mammary gland epithelial cells synthesize albumin; and how its synthesis is affected by bovine mastitis. Albumin expression was monitored using reverse transcription-polymerase chain reaction. Tissues examined were: liver, mammary gland, tongue, intestine, lymph gland, testicle, ovary, and uterus. All tissues except the ovary expressed the albumin gene, albeit less so than the liver. The highest level of expression (other than liver) was found in the lymph nodes but expression was also found in the mammary gland. Incubation of mammary gland explants with the labeled amino acid L-[(35)S] methionine resulted in formation of labeled immunoprecipitable albumin, newly synthesized in the explant. Immunoprecipitable albumin in the medium verified that newly synthesized albumin was also secreted into the medium. This shows that the gland itself is a source of milk albumin. Albumin mRNA expression was approximately 4 times higher in mammary gland tissue from 6 mastitic cows compared with expression in mammary tissue from 6 healthy glands. Further, secretion of albumin was increased 3.5-fold from explants of mastitic mammary glands compared with secretion from explants of healthy mammary glands. Addition of lipopolysaccharide increased the synthesis and secretion of albumin in mammary gland cells in a dose-dependent manner. Exposure to lipopolysaccharide accelerated albumin synthesis in a time-dependent manner up to 48 h. These results lead us to suggest that the secretion of albumin by the mammary gland is part of the innate nonspecific defense system.

Effects of intramammary infection on whey proteinograms of sheep during lactation

“…Albumin levels were significantly higher (P<0.0001) in infected glands than in healthy glands (Table 1, Fig.2), thus confirming an increase in vascular permeability and the passage of blood albumin to the mammary glands (Paape et al 1995, Shirazi-Beheshtiha 2012. This observation may also be attributable to the production of albumin by the gland itself, as observed by Shamay et al (2005), suggesting that albumin secretion in the mammary gland is part of a non-specific defense system.…”

Milk Protein Synthesis in the Lactating Mammary Gland: Insights from Transcriptomics Analyses

“…However, other evidence suggested that the goat mammary gland is able to synthesize a portion of the milk albumin [98]. Expression of albumin in the bovine mammary gland has been previously reported and studied in dairy cows [99]. Observations of increased albumin expression in mammary tissue explants challenged with lipopolysaccharides, and a higher expression observed in glands with mastitis, have led to the suggestion that albumin may have a role in the innate nonspecific defense system [99].…”

“…Expression of albumin in the bovine mammary gland has been previously reported and studied in dairy cows [99]. Observations of increased albumin expression in mammary tissue explants challenged with lipopolysaccharides, and a higher expression observed in glands with mastitis, have led to the suggestion that albumin may have a role in the innate nonspecific defense system [99]. In all species where albumin mRNA was available (i.e., all except kangaroo, Figure 1) a level of expression was detected by the microarray platforms even though at very low levels compared to the highly abundant milk proteins.…”

Innate immunity of the bovine mammary gland

“…Variations in milk serum albumin concentrations is a frequently used marker of exudation of plasma. A low concentration of BSA, around 0.2 mg/mL compared to the 40-45 mg/mL in plasma, is found in the milk of healthy glands, probably leaking from the blood, although part of it may be secreted by the MEC [166]. The increase in serum albumin concentrations is an early event in case of clinical mastitis, temporally coincident with the influx of cells [7,153,170].…”