Objective      To investigate the biological effect of erythropoietin (EPO) on promoting the germ cell development in cryptorchidism induced by flutamide (Flu) in embryonic stage.       Methods      Flu-induced rat offsprings were randomly divided into 3 groups: Flu group (n=36)

Flu+EPO group (n=42)

and Flu+PBS group (n=32). Normal newborn rats were divided into control group (n=40) and EPO group (n=16). The Flu group and control group received conventional breeding

while the Flu+EPO group

EPO group

and Flu+PBS group were treated with 1 000 U/(kg·d) recombinant rat erythropoietin (RrEPO) by intraperitoneal injection on postnatal day (PD) 1

PD 3

PD 5 and PD 7 or an equal volume of PBS. The incidence of cryptorchidism

organ index of testis

and reproduction index were evaluated. The testicular histology

and the area and diameter of seminiferous tubules were observed. And the expression of testis Connexin43 was detected by immunohistochemistry.       Results      The incidence of cryptorchidism in the Flu+EPO group was 38.1% (16/42)

which was lower than 55.6% (20/36) in the Flu group and 53.1% (17/32) in the Flu+PBS group. The germ cell number

organ index

reproduction index

and area and diameter of seminiferous tubules were greater in the Flu+EPO group than the Flu group (P0.01

P0.05)

but there was no significant difference compared with the control group (P0.05). RrEPO promoted normal expression of Connexin43 protein in the testis of the Flu-induced cryptorchidism.       Conclusion      The incidence of Flu-induced cryptorchidism can be decreased by RrEPO treatment after birth. EPO may contribute to promoting the germ cell development after cryptorchidism.