Epididymis is a novel site of erythropoietin production in mouse reproductive organs

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Abstract

The epididymis consists of the interstitial tissue and the ductus epididymidis, an extremely tortuous duct, in which spermatozoa exported from the testis gain motility and fertilizing capacity. We found that the cultured mouse epididymis produces erythropoietin (Epo). The content of Epo mRNA in the epididymis from the adult mouse (8-week-old) amounts to 40% of that in the kidney. The epididymal Epo mRNA dramatically increased upon growth; its level increased 120-fold from the age of 3 weeks to 7 weeks when they complete sexual maturation, while the increase in the total RNA was 3-fold. Hypoxia induced a 5-fold increase in the epididymal Epo mRNA transiently, which is much lower than the induction in the kidney (28-fold). In situ hybridization technique elucidated that the site of Epo production was located in the interstitial space between ductus epididymidis. The epididymal Epo may have an unidentified function in the male reproductive organ.

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Materials and methods

Animals. Animals were maintained and handled in accordance with the guidelines for the care and use of laboratory animals at Kyoto University. Unless otherwise indicated, 8-week-old outbred mice (35–40 g) of the ICR strain (Japan SLC, Shizuoka, Japan) were used.

Culture of the testis and epididymis. The bilateral testes and epididymides from each mouse were extirpated. One testis or epididymis of mouse was cultured in a 24-well culture plate in700μl medium containing the test substance and the

In vitro production of Epo by the male reproductive organs

The testes and epididymides obtained from 8-week-old mice were cultured and at intervals Epo in the culture media was assayed by the enzyme immunoassay method. The assayable Epo in the media increased in a culture time-dependent manner (Fig. 1). Surprisingly, Epo in the culture media of mouse epididymis is 4-fold higher than that of testis. The presence of a protein synthesis inhibitor, cycloheximide, severely inhibits the appearance of Epo in culture media, indicating that Epo in the culture

Discussion

In this paper we have demonstrated that the epididymis is a primary site of Epo production in mouse reproductive organs, but a physiological function of the epididymal Epo remains to be studied. The main tissue comprising the epididymis is ductus epididymidis, a long and highly convoluted duct. The caput epididymidis is connected to the rete testis via several ductuli efferentes [33]. The caput and corpus are involved in the maturation process of spermatozoa. Spermatozoa leaving the testis are

Acknowledgements

This work was supported by grants-in-aid from Ministry of Education, Science, Culture, and Sports of Japan, from the “Research for the Future” program in The Japan Society for the Promotion of Science and from Japan Health Sciences Foundation.

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