Rabbit Whey Acidic Protein Concentration in Milk, Serum, Mammary Gland Extract, and Culture Medium

¹ Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas, Cedex France

Rabbit whey acidic protein has been purified from whey using an AcA54 column. The purified whey acidic protein had an amino acid composition in agreement with the previously defined cDNA sequence. An antibody against whey acidic protein was raised in guinea pig. This antibody did not crossreact with mouse or cow milk or with rabbit _s1-casein and ßcasein. Whey acidic protein concentration was measured in rabbit milk using the antibody with a radioimmunoassay. The concentration of whey acidic protein in rabbit milk was 15 mg/ ml, whereas the concentrations of _s1-casein and ß-casein were 16 and 45 mg/ml, respectively. The concentration of the three proteins was also evaluated in culture medium of rabbit primary mammary cells. The three proteins were induced by prolactin alone. Glucocorticoids amplified the prolactin effect on whey acidic protein more intensively than on caseins. The three proteins were present in mammary extract from virgin rabbit. The concentration of these proteins was lower at d 8 and 14 of pregnancy, and it was very high at d 25 of pregnancy. Whey acidic protein was undetectable in blood of virgin, weaned, and midpregnant females and of males. Whey acidic protein was present in blood of lactating rabbits, but _s1-casein and ß-casein were not detectably present in rabbit blood at the examined physiological states.

Key Words: rabbit • whey acidic protein • radioimmunoassay

Submitted on February 25, 1991
Accepted on June 21, 1991