Comparison of bovine LAPTM4B protein expression. Total protein extracts (50 μg/well) from granulosa cells of 2–4 mm small follicles (SF), dominant follicles at Day 5 of the estrous cycle (DF), ovulatory follicles 24 h after hCG injection (OF), CL at Day 5 and the recombinant LAPTM4B fragment were size-fractionned on a 15% denaturing SDS-PAGE gel and immunoblotted using the anti-bovine (LA)2-LAPTM4B polyclonal antibody as described under Materials and Methods. A. The recombinant tandem fragment (LA)2-LAPTM4B was specifically recognized at 15.3 kDa. B. The results for the protein extracts of representative follicles and CL are shown. The native bovine LAPTM4B showed two forms migrating at 26.3 kDa and at 31.5 kDa. A stronger signal of the 26.3 kDa protein was observed in DF, and the weakest signal was observed in OF. Expression of the 31.5 kDa form was not statistically different among samples. C. The relative intensities of the 26.3 kDa and 31.5 kDa bands were quantified by densitometry and are represented. The results are presented as means ± SEM of two independent samples per group, and bars with different letters indicate significantly different values (P < 0.05).