ACSL1, AGPAT6, FABP3, LPIN1, and SLC27A6 are the most abundant isoforms in bovine mammary tissue and their expression is affected by stage of lactation.

The lactating bovine mammary gland is a formidable triacylglycerol-synthesizing machine and, as such, represents an ideal model for studying putative functions of distinct isoforms of solute carrier family 27 transporters [(SLC27A) 1, 2, 3, 5, 6], long chain acyl-CoA synthetases [(ACSL) 1, 3, 4, 5, 6], fatty acid binding proteins [(FABP) 1, 3, 4, 5, 6], 1-acylglycerol-3-phosphate O-acyltransferases [(AGPAT) 1, 2, 3, 4, 5, 6, 7, 8], and lipins [(LPIN) 1, 2, 3]. The relative percentage of mRNA abundance and fold-changes in the expression of isoforms in mammary tissue from 6 cows each at -15, 15, 60, and 240 d relative to parturition were analyzed using quantitative PCR. Transcripts of FABP isoforms were most abundant, accounting for 78% of the 28 genes measured, and SLC27A isoforms were least abundant (< 0.5% of genes measured). mRNA of AGPAT, ACSL, and LPIN accounted for approximately 12, 7, or approximately 2%, respectively, of all genes measured. The mRNA abundance at 60 d postpartum for FABP3, ACSL1, AGPAT6, and LPIN1 was 80-, 7-, 15-, and 20-fold greater relative to -15 d. Transcripts of these isoforms constituted the most abundant within each specific gene family. SLC27A2, SLC27A5, and SLC27A6 had peak expression at 240, 240, or 15 d relative to parturition, respectively. Results suggest that SLC27A6, ACSL1, FABP3, AGPAT6, and LPIN1 coordinately regulate the channeling of fatty acids toward copious milk fat synthesis in bovine mammary.