title: Alpha-lactalbumin production by rat mammary gland: prepartum emergence of resistance to glucocorticoids and progestins.
abstract: Explants of mammary glands from pregnant or lactating rats were shown to differ markedly in their response to glucocorticoid and progestin in terms of alpha-lactalbumin production. Tissue from day 14 pregnant rats had low initial tissue levels and basal production of alpha-lactalbumin, and showed a dose-biphasic response to glucocorticoids, with significantly higher production at 3 nM than 300 nM RU26988; the progestin ORG 2058 inhibited production. In explants from lactating rats (day 1 and day 5) tissue content and basal production of alpha-lactalbumin were markedly increased compared with day 14 pregnant, but were unaltered by glucocorticoid or progestin. Animals near parturition (day 19, day 20) showed a transitional pattern, with considerable variation between animals. Basal production and tissue content correlated closely; as levels rose, the tissues became progressively less responsive to the effects of both classes of steroid. We interpret these data as evidence for a switch, in terms of glucocorticoid control of alpha-lactalbumin gene expression pre-partum; the mechanism(s) underlying this switch remain to be explored.
authors.affiliation: Medical Research Centre, Prince Henry's Hospital, Melbourne, Vic., Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Quirk
authors.forename: J E
authors.initials: JE
authors.lastname: Gannell
authors.forename: J W
authors.initials: JW
authors.lastname: Funder
mesh_terms: D000732:Androstanols / Q000494:pharmacology; D000818:Animals; D005260:Female; D005938:Glucocorticoids / Q000502:physiology*; D007768:Lactalbumin / Q000096:biosynthesis*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D011282:Pregnenediones / Q000494:pharmacology; D011372:Progestins / Q000502:physiology*; D051381:Rats
chemical_list: D000732:Androstanols; D005938:Glucocorticoids; D011282:Pregnenediones; D011372:Progestins; C020175:16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione; C049154:11,17-dihydroxy-6-methyl-17-(1-propynyl)androsta-1,4,6-triene-3-one; D007768:Lactalbumin