Temperature sensitivity of primary spermatocyte DNA synthesis in immature mice confirmed by bromodeoxyuridine labelling in vitro.
OBJECTIVE
To investigate the relationship between temperature and DNA synthesis of immature germ cells and to determine whether the early primary spermatocytes proliferate at a 'scrotal' temperature of 32 degrees C in vitro.


METHODS
Day-7 mouse testes (n = 16) were cultured with 10% fetal calf serum (FCS) for 3 days at 32 degrees C or 37 degrees C and labelled by bromodeoxyuridine (BrDU) for a further hour. The BrDU-labelled cells were detected by immunohistochemical staining using a monoclonal anti-BrDU antibody. The numbers of primary spermatocytes with BrDU-labelling or unlabelled in each tubule were determined as an index of spermatocyte DNA synthesis. In addition, the cultured media at different temperatures were collected and the testosterone levels measured by radioimmunoassay.


RESULTS
The numbers of primary spermatocytes (P < 0.01) and the BrDU-labelling index in primary spermatocytes per tubule at 32 degrees C in vitro were significantly higher (P < 0.001) than in the culture at 37 degrees C. The testosterone levels in the culture media at 32 degrees C were also markedly higher than in the culture at 37 degrees C (P < 0.01).


CONCLUSIONS
These observations indicate that DNA synthesis of early primary spermatocytes and testosterone production can be stimulated by lower testicular temperature, even in immature mouse testes that are naturally located in the intra-abdominal cavity.
Zhou
B
B
F. Douglas Stephens Surgical Research Laboratory, Royal Children's Hospital Research Institute, Melbourne, Australia.
Hutson
J M
JM
Hasthorpe
S
S
Farmer
P J
PJ
D000818:Animals; D001831:Body Temperature; D001973:Bromodeoxyuridine / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D013090:Spermatocytes / Q000166:cytology*; D013737:Testis / Q000502:physiology; D013739:Testosterone / Q000378:metabolism
D013739:Testosterone; D004247:DNA; D001973:Bromodeoxyuridine