Expression of transforming growth factor-alpha-like messenger ribonucleic acid transcripts in the bovine mammary gland.

The objective of this study was to evaluate the expression of mRNA for transforming growth factor-alpha in the bovine mammary gland. Total RNA from 23 cows at various stages of development was isolated from mammary parenchyma and subjected to Northern blot analysis using human transforming growth factor-alpha 32P-labeled deoxycytosine triphosphate cDNA probe. When blots were washed through 1x sodium chloride and sodium citrate plus 1% SDS at 60 degrees C, a 4.8-kb band was observed in all RNA samples. When stringency was increased to .1x, mRNA transcripts were observed only for cows at d 233, 240, and 244 of gestation. After the high stringency washes, major bands were observed at 7.4 and 3.3 kb and minor bands on d 233 at 5.4, 2.3, and 1.6 kb. No additional transcripts were detected in RNA from mammary glands of nonpregnant cows during involution, lactating cows, or estrogen-treated heifers. These data indicate that transcripts similar to transforming growth factor-alpha are present in the bovine mammary gland. The expression pattern could represent alternatively spliced transcripts that were produced during an important period of mammary development prior to parturition.