A. A cohort of mice were left untreated (No hormones) or treated acutely (48–50 h) with estradiol benzoate (E, 1 μg, Sigma, St. Louis, MO) and P (1 mg, Sigma) in 100 μl sesame oil via a single interscapular subcutaneous injection behind the neck once (E+P, 48 hrs) or 3 times, 48 hours apart (E+P, 3× 48 hrs). Two hours before sacrifice, the mice were injected with BrdUrd (0.03 mg/g of body weight) intraperitoneally. Following treatment, the contralateral inguinal gland was removed (Cdk2+/+ mice, n = 3; Cdk2+/- mice, n = 3; Cdk2-/- mice, n = 3, 11–32 weeks of age at day 0 of experiment) and whole-mount were prepared. B. and C. Proliferation is quantified by BrdU staining.