Endocrinology, Vol 101, 1784-1791, Copyright © 1977 by Endocrine Society
Bioassay for prolactin: densitometric analysis on polyacrylamide gels of milk protein production by mammary explants in vitro
MR Green, JV Pastewka and AC Peacock
Mammary explants from mice in midpregnancy cultured in a synthetic medium
containing insulin and hydrocortisone respond to the addition of prolactin
by the synthesis of milk proteins. The secretory response in alveolar
lumina has served as a histologic endpoint in a sensitive bioassay for
prolactin developed by Kleinberg and Frantz (J Clin Invest 50: 1557, 1971).
This report demonstrates that the quantitative densitometric analysis of
stained milk proteins (caseins) made in response to prolactin is a useful
modification of that bioassay. Electrophoretic analysis of the proteins
extracted from the explants permits a quantitative estimate of casein
content. The amount of casein present after 5 days of incubation was found
to be a measure of the prolactin concentration in the medium. No
radioactive isotopes are used. The use of electrophoretic analysis has
practical advantages over the histologic scoring used earlier, and has
approximately the same range of sensitivity.
