A, Principal component analysis of extracellular metabolic profiles of isolated healthy (n=3; blue) and regressed (n=3; green) mammary glands after cultivation in cell growth medium for 8 h (Methods). The metabolomics analysis was targeted to central carbon metabolites. Centroids represent the mean and concentration ellipses represent one standard deviation (level=0.68) of an estimated t-distribution based on the first two principal components. Data information: Numbers of replicates correspond to individual mice or humans. 