Techniques for preparation of bovine mammary smooth membranes

Most procedures for fractionation of lactating mammary tissue membranes have utilized centrifuge tubes of small volume. We report a method for large-scale fractionation of bovine mammary membranes by a zonal rotor. Because of the large volume of the zonal rotor (1350 ml), greater amounts of starting material can be fractionated to obtain greater yields of desired fractions. We report results of linear sucrose gradients to fractionate mammary tissue homogenates and step gradient adaptations to accelerate membrane separations. Assay of membrane fractions for marker enzyme activities demonstrated that zonal fractionation and derived techniques were applicable for large scale preparation with higher yields of selected bovine mammary membranes. Application of this technique to small volumes is discussed for laboratories without a zonal rotor.