Milk protein synthesis by mammary glands of vitamin D-deficient mice.
Mammary glands from second generation vitamin D-deficient mice and rats were examined for their ability to make the major milk proteins, casein and alpha-lactalbumin, both in vivo and in vitro. The glands from the rachitic animals were morphologically indistinguishable from those of age-matched controls. When placed in explant culture, glands from vitamin D-deficient mice and rats underwent DNA synthesis at a rate comparable to that of glands from the vitamin D-replete controls. However, the hormonally induced synthesis of casein and alpha-lactalbumin was significantly reduced in explants of glands from rachitic vs. control animals. The reduction in casein-synthesizing ability by mouse mammary gland explants was not reversed by the addition of 10(-8) or 10(-6) M 1,25-dihydroxycholecalciferol to the culture medium, but could be reversed by pretreating the vitamin D-deficient mice with the D metabolite in vivo for 10 days before the onset of culture. The decrease in milk protein synthesis in culture is paralleled in vivo by a decrease in milk protein content in the milk and lactating mammary glands of vitamin D-deficient mice and rats. Both in vivo and in vitro, it is the two highest mol wt caseins that are most affected by the lack of vitamin D in the diet. These data suggest that vitamin D does not play a fundamental role in growth and morphological development of the normal mammary gland, but, rather, it is important in maintenance of full hormonally induced functional differentiation of the mature gland.
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002364:Caseins / Q000096:biosynthesis*; D046508:Culture Techniques; D004247:DNA / Q000096:biosynthesis; D005260:Female; D007768:Lactalbumin / Q000096:biosynthesis*; D007774:Lactation / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D011247:Pregnancy; D051381:Rats; D012279:Rickets / Q000378:metabolism*
D002364:Caseins; D004247:DNA; D007768:Lactalbumin; D002117:Calcitriol