Thyroid hormones enhance the synthesis and secretion of alpha-lactalbumin by mouse mammary tissue in vitro.
The syntheses and secretion of casein and alpha-lactalbumin were examined in organ culture of midpregnancy mouse mammary glands using serum-free medium supplemented with various combinations of insulin, hydrocortisone, PRL, and L-T3. Using highly specific antibodies raised against mouse caseins and alpha-lactalbumin, we demonstrate a selective enhancement of alpha-lactalbumin and lactose synthesis and secretion when all four hormones are present in the culture medium. Production of casein was not modified by the presence of L-T3. Hydrocortisone at concentrations of 10(-9)-10(-6) M inhibited the secretion of both casein and alpha-lactalbumin into the culture medium. The addition of L-T3 to the medium selectively overcame the inhibition of alpha-lactalbumin secretion by hydrocortisone. Extracts of tissue cultured in the presence of L-T3 contained two distinct forms of alpha-lactalbumin, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the absence of L-T3, synthesis of a single form of alpha-lactalbumin prevailed. In the culture medium, predominantly one form of alpha-lactalbumin was detected regardless of the presence of L-T3 during culture. These data clearly indicate that thyroid hormones play an important regulatory role in functional differentiation of the mouse mammary gland.
D000818:Animals; D002364:Caseins / Q000096:biosynthesis; D003470:Culture Media / Q000032:analysis; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007768:Lactalbumin / Q000096:biosynthesis*; D007785:Lactose / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D009924:Organ Culture Techniques; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology*
D002364:Caseins; D003470:Culture Media; D007328:Insulin; D014284:Triiodothyronine; D011388:Prolactin; D007768:Lactalbumin; D007785:Lactose; D006854:Hydrocortisone