TRANSFORMING GROWTH-FACTOR-ALPHA AND GROWTH-FACTOR-BETA-1 ARE DIFFERENTIALLY EXPRESSED IN THE BOVINE MAMMARY-GLAND DURING MAMMOGENESIS, LACTOGENESIS, GALACTOPOIESIS AND INVOLUTION

Anatomical change and the scale of metabolic and biosynthetic reprogra mming of the mammary gland during the life cycle imply an enormous tis sue remodeling in the adult mammal. Growth factors are involved in the local control of the gland. Our aim was to analyze expression of tran sforming growth factors alpha and beta-1 (TGFa, TGFb-1) during differe nt stages of growth and function. Tissue was obtained after slaughter from non-pregnant control heifers, from pregnant heifers (mammogenesis ) and from cows during lactogenesis, galactopoiesis and involution (da y 21, non-pregnant). Additional samples were obtained after mammary bi opsies during involution (days 3, 7, 21, non-pregnant) and during rede velopment of a pregnant, dry cow. Other samples were obtained from hei fers after induced mammogenesis and lactogenesis, with and without add itional prolactin inhibition. Total RNA was isolated from mammary tiss ue and analyzed by reverse transcription-polymerase chain reaction and ribonuclease protection assay. TGFb-1 mRNA levels were highest during involution, especially during early involution (days 3 and 7). Lowest levels were detected during lactogenesis and galactopoiesis, with int ermediate levels in the gland of control heifers and pregnant heifers. Highest TGFa expression was detected in glands of control heifers and dry cows. TGFa expression decreased during pregnancy and reached very low levels during lactation. TGFa mRNA increased in biopsy samples du ring involution of non-pregnant animals and increased further in the r edeveloping, dry gland of a cow 2 weeks before parturition. TGFa mRNA levels were higher after induced mammogenesis than after induced lacto genesis. TGFa mRNA expression increased further during prolactin inhib ition. These data suggest that TGFa may be important for development a nd TGFb-1 mainly important for involution of the bovine mammary gland. (This work was supported by the German Research Fundation; Scha 257/1 3-1). Published by Elsevier Science B.V.