Mammary gland whey acidic protein: ontogeny and changing patterns of steroid sensitivity.
Whey acidic protein (WAP) has been measured by radioimmunoassay in the mammary gland of rats over pregnancy and lactation, and in mammary gland explants incubated with glucocorticoid or progestin in vitro. The radioimmunoassay used a novel fusion protein, glutathione transferase-WAP (GT-WAP), which can be iodinated with ease, unlike the native protein. Mammary gland WAP levels were low (less than 100 ng/mg tissue) until 2-3 days before parturition, but rose to 3 micrograms/mg tissue at day 21 of pregnancy. Immediately after parturition WAP content decreased to 1 micrograms/mg tissue, and then increased to greater than 5 micrograms/mg tissue during mid-lactation. Similarly, alpha-lactalbumin content was low throughout pregnancy (less than 10 ng/mg tissue) until day 20. Thereafter, values rose on the last day of pregnancy and the first day of lactation, fell briefly in early lactation like WAP, and rose to plateau levels by day 11 of lactation. In vitro explants prepared from mid-pregnant rats (day 14) synthesized WAP in the presence of insulin and prolactin. The synthetic glucocorticoid RU26988 (11 beta,17 beta-hydroxy-17 alpha-(1-propynyl)-androsta-1,4,6-trien-3-one) progressively increased WAP production to a maximum of greater than 10-fold basal (in the presence of insulin and prolactin) at 300 nM, in contrast with alpha-lactalbumin which showed a biphasic dose-response curve in explants from mid-pregnant rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Quirk
S J
SJ
Medical Research Centre, Prince Henry's Hospital, Melbourne, Vic., Australia.
Slattery
J A
JA
Funder
J W
JW
D000818:Animals; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D007328:Insulin / Q000502:physiology; D007768:Lactalbumin / Q000494:pharmacology; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism*; D011247:Pregnancy; D011372:Progestins / Q000502:physiology; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D013256:Steroids / Q000494:pharmacology
D005938:Glucocorticoids; D007328:Insulin; D008894:Milk Proteins; D011372:Progestins; D013256:Steroids; C024471:whey acidic proteins; D007768:Lactalbumin