Expression of BERV-K1 and -K2 env mRNAs in normal bovine tissues. Total RNA was extracted from tissues of Holstein cows. Abbreviations: COT, cotyledon; ICOT, intercotyledon; CAR, caruncular; ICAR, intercaruncular; Lu, lung; Li, liver; Sp, spleen; He, heart; Mu, muscle; Ki, kidney; Sk, skin; Te, testis; EM, endometrium. Each value was normalized to the amount of GAPDH mRNA and is exhibited as means ± standard errors of data from three or six samples in duplicate experiments.