Expressions of mRNA for ErB1, ErbB2, and ErbB4 in various spermatogenic stages and testicular cell types. The expressions of ErbB1 (200 bp), ErbB2 (150 bp), and ErbB4 (150 bp) were analyzed by semi-quantitative RT-PCR. Total RNA was extracted from the testes containing early spermatogonial (1st – 4th generation), late spermatogonial (5th – 7th generation), and primary spermatocyte stages (A and B), and from the fractionated spermatogonia and Sertoli cells, the latter of which were cultured for 10 days and 1 month (C). The cycle numbers in PCR were 35 (A) and 33 (B), and 35 for ErbB1 and ErbB2 and 40 for ErbB4 (C). Elongation factor-1α (EF-1α, 550 bp, 25 cycles) is the internal control. SCF is a Sertoli cell-specific marker. Data are representative of at least 3 independent experiments.