PROTEIC COMPOSITION OF CORPORA-AMYLACEA IN THE BOVINE MAMMARY-GLAND

Histochemical studies of mammary gland sections obtained from healthy lactating Prim'Holstein cows contained numerous corpora amylacea, main ly located in active alveoli. Observations by electron microscopy reve aled a cauliflower shape, with a fibrillar or multilayered organizatio n. Mineral studies confirmed the presence of high calcium levels (12.3 % of dry matter) and phosphorus (7.4%) in the corpora amylacea composi tion, These bodies stained positive to Von Kossa silver nitrate and to Periodic acid-Schiff. However, depending on the gland of origin, corp ora amylacea stained positive or negative to Congo red. Histochemical studies seemed, therefore, insufficient to determine the presence or a bsence of amyloid, The amount of total protein varied by approximately 25%, Immunoblotting and analysis of the amino acid sequence of a pept idic fragment obtained from corpora amylacea gave clear evidence of th e occurrence of caseins, P-lactoglobulin and a-lactalbumin. However, t he comparison between the amino acid composition of corpora amylacea a nd those of the main milk proteins indicated the presence of other pro teins. Electrophoretic analysis also gave evidence of the presence of several other proteins, i.e. glycoproteins. Therefore, it is probable that corpora amylacea composition is much more complex than previously reported.