Fig. 4. Uterine status of PGs and expression of genes encoding sPLA₂s, and restoration of normal implantation in Pla2g4a^–/– mice by PGs. (A,B) The levels of PGs in uteri of wild-type and Pla2g4a^–/– mice on days 4 and 5 of pregnancy, respectively. PGI2 was measured as 6-keto-PGF₁. N.D., not detectable (unpaired t-test, *P<0.05; **P<0.01; n=4-5). (C) Expression of genes encoding sPLA₂ isoforms in various wild-type mouse tissues by RT-PCR. Heart (H), intestine (I), kidney (K), liver (Li), lung (Lu), spleen (S) and testis (T) tissue samples were used as controls along with uterine (U) samples obtained on day 4 of pregnancy. Actb, mouse ß-actin. (D) In situ hybridization of Pla2g10 (sPLA₂-X) in uteri of wild-type mice on days 4 and 5 of pregnancy. Note uterine expression of Pla2g10 similar to that of Pla2g4a and Ptgs1 on day 4 (compare with Fig. 3A). The arrow indicates the location of a blastocyst. ge, glandular epithelium; le, luminal epithelium; s, stroma; myo, myometrium. (E) Restoration of normal implantation in Pla2g4a^–/– mice. Pla2g4a^–/– mice were injected with saline or PGE2 plus cPGI twice (10:00 and 18:00 hours) on day 4 and implantation sites were examined on day 5 (10:00 hours). The numbers above the bars indicate the number of Pla2g4a^–/– mice with implantation sites/total number of Pla2g4a^–/– mice used (unpaired t-test; *P<0.001). The mice without implantation sites or blastocysts were excluded from the experiments. (F) Representative photographs of day 5 uteri of Pla2g4a^–/– mice given the vehicle or PGs on day 4 of pregnancy. Note increased number of implantation sites with prominent blue reaction after PG treatment. Brackets indicate crowding of implantation sites.