Sexual dimorphism in amino acid compositions of mouse prolactin

Sexual dimorphism was found in amino acid compositions and immunogenecity of variant types of prolactin (PRL) purified from the pituitary gland of normal adult C57BL mice by a high performance liquid chromatography. From the pituitary gland of female mice, three female variant types of PRL were isolated, whereas from the pituitary gland of male mice, two male variant types of PRL (M1-PRL and M3-PRL) and a female variant type of PRL (M2-PRL) were obtained. The amino acid composition of M3-PRL was different from any of female variant types which were very similar to each other and contained less varine, isoleucine, leucine, tyrosine and lysine but more alanine than the latter. Immunoreactivity of any of female variant types of PRL against anti-PRL serum was 100%, whereas that of M1-PRL was as much as 85% and that of M3-PRL was nearly undetectable.