Dominant follicles were retrieved from the ovaries of women undergoing laparoscopic tubal sterilization before the LH surge or at various times after recombinant hCG administration. The paraffin embedded sections of dominant follicles obtained from various time points (A, preovulatory phase n=2; B, early ovulatory phase n=4; C & D, late ovulatory phase n=4; E, late ovulatory phase n=1) were subjected to immunohistochemical analyses to detect ACE2 protein. Sections in C & D are from different patients obtained from the late ovulatory period. F is an antrum region of the postovulatory follicle shown in the panel E. Pink/red staining indicates positive signals for ACE2. All sections were lightly stained with hematoxylin (blue staining) for nuclear counterstaining. Arrows point to granulosa and theca cells where the intense staining for ACE2 is detected. Wavy arrows point to ACE2 staining in the stroma layer. GC, granulosa cells; TC, theca cells; GLC, granulosa lutein cells; TLC, theca lutein cells; RBC, red blood cells. Scale bar in A; 100 μm