Figure 10.

Precocious activation of STAT3 and activation of MMP2 suggest early onset of involution. A) The number 4 mammary gland was removed from Src-/- and Src+/+ mice at P18 (lanes 1–6), L2 (lanes 7–12) and L9 (lanes 13–18). Three separate mice were used per genotype and developmental stage. Protein lysates were prepared as described in the Materials and Methods sections, and immunoblotting conducted to detect phosphorylated STAT3 (tyrosine7⁷⁰⁵) (top panel), the total amount of STAT3 expression (middle panel), and the amount of ERK 1&2 as a loading control (bottom panel). B) Mammary gland lysates were prepared from Src+/+ (top panel) and Src-/- (bottom panel) mice at L9. I1, I2, I4, I6, I8, and I14. The positions of the 72 kDa molecular weight proenzyme and 62 kDa molecular weight active enzyme are indicated on the left side of the panels.