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Hormonal induction of α–lactalbumin and β–lactoglobulin in cultured mammary explants from pregnant pigs

Published online by Cambridge University Press:  01 June 2009

Susan C. Dodd
Affiliation:
Endocrinology and Animal Physiology Department, Institute for Grassland and Animal Production, Hurley, Maidenhead SL6 5LR, UK Department of Nutrition, Institute of Food Research, Reading Laboratory, Shinfield, Reading RG29AT, UK
Isabel A. Forsyth
Affiliation:
Department of Cellular Physiology, AFRO Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK
Hugh L. Buttle
Affiliation:
Endocrinology and Animal Physiology Department, Institute for Grassland and Animal Production, Hurley, Maidenhead SL6 5LR, UK
Michael I. Gurr
Affiliation:
Department of Nutrition, Institute of Food Research, Reading Laboratory, Shinfield, Reading RG29AT, UK
Raymond R. Dils
Affiliation:
Department of Biochemistry and Physiology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, PO Box 228, Reading RG6 2AJ, UK

Summary

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 α-lactalbumin and β-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 β-lactoglobulin could be detected consistently from day 90 (13 ± 12 ng/μg DNA, n = 4) and α-lactalbumin from day 100 (1·3 ± 0·5 ng/μg DNA, n = 11). At all stages of pregnancy, both whey proteins increased markedly during the period of culture (up to 7 d). Stimulation of α-lactalbumin appeared to be primarily under prolactin control. Prolactin increased α-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 β-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.

Type
Original Articles
Copyright
Copyright © Proprietors of Journal of Dairy Research 1994

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