Hormonal induction of alpha-lactalbumin and beta-lactoglobulin in cultured mammary explants from pregnant pigs.
Mammary tissue from pigs on days 60, 80, 90, 100 and 100+ (days 106-111) of pregnancy has been cultured in vitro as explants. The total accumulation in tissue and culture medium of the whey proteins alpha-lactalbumin and beta-lactoglobulin has been measured using specific radioimmunoassays. The control, uncultured tissue showed progressive morphological development from sparse, non-secretory epithelial tissue on day 60 to full lobulo-alveolar development with some accumulated secretion from day 100. In uncultured explants beta-lactoglobulin could be detected consistently from day 90 (13 +/- 12 ng/micrograms DNA, n = 4) and alpha-lactalbumin from day 100 (1.3 +/- 0.5 ng/micrograms DNA, n = 11). At all stages of pregnancy, both whey proteins increased markedly during the period of culture (up to 7 d). Stimulation of alpha-lactalbumin appeared to be primarily under prolactin control. Prolactin increased alpha-lactalbumin accumulation to a similar extent alone, or in the presence of insulin and/or corticosterone. The response to prolactin was dose-dependent over the range 0.4-20 nM (10-500 ng/ml). Porcine prolactin was more potent than ovine prolactin. There was no effect of porcine growth hormone and no synergism detected between prolactin and tri-iodothyronine. By contrast, no specific hormonal requirements were established for accumulation of beta-lactoglobulin, which appeared to increase in vitro if tissue remained viable in various combinations of insulin, corticosterone and prolactin. It was not stimulated by growth hormone. There was some indication of a prolactin-sensitive component in longer term cultures after day 4.
Dodd
S C
SC
Endocrinology and Animal Physiology Department, Institute for Grassland and Animal Production, Hurley, Maidenhead, UK.
Forsyth
I A
IA
Buttle
H L
HL
Gurr
M I
MI
Dils
R R
RR
D000818:Animals; D003345:Corticosterone / Q000494:pharmacology; D003470:Culture Media; D046508:Culture Techniques; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007768:Lactalbumin / Q000096:biosynthesis*; D007782:Lactoglobulins / Q000096:biosynthesis*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology*; D013552:Swine / Q000378:metabolism*; D013997:Time Factors
D003470:Culture Media; D007328:Insulin; D007782:Lactoglobulins; D011388:Prolactin; D013006:Growth Hormone; D007768:Lactalbumin; D003345:Corticosterone