Reduction of total lymphocyte migration to the uterus during the first days of pregnancy and pseudopregnancy of the rabbit (Oryctolagus cuniculus)

Abstract

THE INITIATION OF PREGNANCY IS A TRANSITIONAL PERIOD DURING WHICH VERY IMPORTANT CHANGES IN SEXUAL HORMONE LEVELS ARE REGISTERED. THESE CHANGES CAUSE MULTIPLE MORPHOLOGIC CHANGES IN THE ENDOMETRIUM THAT ARE QUITE NECESSARY FOR IMPLANTATION TO OCCUR. THE OBJECTIVE OF THE PRESENT STUDY WAS TO EVALUATE THE MIGRATION ACTIVITY OF TOTAL LYMPHOCYTES IN THE ENDOMETRIUM OF NEW ZEALAND BREED, FOUR MONTHS OLD, WHITE FEMALE RABBITS MAINTAINED IN INDIVIDUAL CAGES IN LABORATORY ANIMAL CONDITIONS WITH CYCLES OF 12 HOURS LIGHT AND 12 HOURS DARKNESS, WITH FEED AND WATER AD LIBITUM. WITH THESE ANIMALS THREE DIFFERENT GROUPS WERE FORMED: A) PREGNANT ANIMALS ON DAY 1, 2, 3, 4, 5 AND 8; B) ANIMALS IN A PSEUDO-PREGNANT STATE ON DAYS 1, 2, 3, 4, 5 AND 8 FOLLOWING THE ADMINISTRATION OF 100 IU OF HUMAN CHORIONIC GONADOTROPIN (HCG); AND C) NON PREGNANT ANIMALS (NP). THE RABBITS WERE SLAUGHTERED AT DIFFERENT TIMES ACCORDING TO THE EXPERIMENTAL PROTOCOL THROUGH A LETHAL SODIUM PENTOBARBITAL INTRACARDIAC INJECTION ONCE THE RABBIT WERE ANESTHETIZED. AFTER THE SLAUGHTER, FRAGMENTS OF BOTH UTERINE HORNS WERE EXCISED, AND FRAGMENTS OF UTERINE TISSUE WERE OBTAINED, FIXED AND PROCESSED BY PARAFFIN INCLUSION TO PERFORM HISTOLOGICAL CUTS THAT WERE STAINED WITH HEMATOXYLIN-EOSIN (H & E) AND GIEMSA. TOTAL LYMPHOCYTES PRESENT IN THE LUMINAL EPITHELIAL LAYER AND LAMINA PROPIA OF THE STROMA OF THE ENDOMETRIUM WERE COUNTED. THE NUMBER OF TOTAL LYMPHOCYTES PRESENT IN THE RABBIT ENDOMETRIUM DURING DAYS 1 TO 5 AND 8 OF GESTATION AND PSEUDO-GESTATION DECREASED (P < 0.05) WITH RESPECT TO THE VALUES FOUND IN NON-PREGNANT, CONTROL FEMALES (NG). HOWEVER, IN THE PSEUDOPREGNANT ANIMALS A DECREASE IN THE NUMBER OF LYMPHOCYTES FOUND ON DAYS 1 AND 2 WAS MORE EVIDENT THAN WHAT WAS OBSERVED FOR THESE DAYS IN THE PREGNANT RABBITS. DAY 8TH WAS CHARACTERIZED BY PRESENTING A SMALLER QUANTITY OF CELLS THAN THE REST OF THE EVALUATED DAYS. IT IS CONCLUDED THAT DURING IN THE FI RST 8 DAYS OF GESTATION THE NUMBER OF LYMPHOCYTES PRESENT IN THE RABBIT ENDOMETRIUM DECREASES AND THAT PSEUDO-PREGNANT RABBITS PRESENT A SIMILAR CONDITION.