Fig. 6. Changes in milk nutrition and gene expression at mid-lactation. (A) Analysis of milk volume, water and ion content in milk collected from wild-type (white bars) and Hif1a^–/– glands (gray bars) at mid-lactation, mean±s.e.m. (B) RTD-PCR was used to determine the levels of Pgk, Glut1, claudin 7 and claudin 8 mRNA in mid-lactation tissue, relative to Ck19 expression.