Occurrence of Early Pregnancy-Associated Thrombocytopenia in Splenectomized Rabbits.

Abstract

The occurrence of early pregnancy-associated thrombocytopenia (EPAT) in adult female rabbits was examined in the present study. The rabbits were divided into 5 groups: (i) 5 rabbits were superovulated with follicle stimulating hormone (FSH) and human chorionic gonadotropin (hCG) and mated, but the embryos were not recovered; (ii) 6 rabbits were superovulated and mated, and the embryos were recovered; (iii) 8 rabbits were splenectomized and mated, and the embryos were recovered; (iv) 6 rabbits were splenectomized and injected with hCG; and (v) 3 control rabbits underwent sham operations and they were injected with hCG. In each case, blood (2 ml) was obtained by venipuncture from the marginal ear vein from the day of hCG injection to the day of embryo collection. A significant change of peripheral platelet concentration (PLT) was characterized either by a decrease or by an increase of >20% compared with the value of the initial sampling time. The proportions of rabbits which displayed a significant change in PLT were 80% (4/5) in Group i, 83% (5/6) in Group ii, 100% (8/8) in Group iii, 83% (5/6) in Group iv and 67% (2/3) in Group v(P>0.05). In Groups i and ii, 91% (10/11) of rabbits showed an increase of PLT. In Group iii, 75% (6/8) of rabbits showed a decrease of PLT (EPAT). In Groups iv and v, although each rabbit showed a decrease of PLT, the PLT patterns were variable. Effects of group (interaction of treatment/condition × pregnant status) and pregnant status on PLT were significant (P<0.0004 and P<0.0003 respectively). No effect of time after hCG injection on PLT was detected. Significant differences of PLT were observed only between Group i or ii and other groups, when least square mean was compared with a variance of time after hCG injection. From the results of the present study, splenectomy for the pregnant rabbits was requisite for an occurrence of EPAT. Also, the results suggest that EPAT does not occur in normal rabbits. Observations in splenectomized rabbits suggest that platelet activation may be occurring in early pregnancy but not to a sufficient degree to cause measurable thrombocytopenia in peripheral blood.