Development of testicular lesions in F344 rats after treatment with boric acid.
Boric acid is an inorganic acid that impairs fertility in male rodents. A reproductive assessment by continuous breeding study found that male rats treated with boric acid had decreased fertility and sperm motility. In order to determine the cell type that is first affected by boric acid, we have examined the development of the boric acid-induced testicular lesion by light and electron microscopy. Adult F344 male rats were fed 9000 ppm boric acid in NIH-07 rat chow for up to 4 weeks. The first testicular lesion noted was an inhibition of spermiation, which appeared by Day 7. Widespread exfoliation of apparently viable germ cells, and pachytene cell death in stages VII and XIV, appeared as exposure continued. After 28 days of dosing, extreme epithelial disorganization and germ cell loss were evident. To determine if there was a hormonal component to the boric acid-induced testicular lesion, serum levels of basal, hCG-, and LHRH-stimulated testosterone levels were measured. After 4 days of dosing, basal testosterone levels were lower than controls and remained low during dosing. However, serum testosterone levels were similar in both boric acid-treated and control animals after either hCG or LHRH challenge. To determine if boron was preferentially accumulated by the testis, boron levels in testis, epididymis, liver, kidney, and blood were measured. Boron levels had effectively reached steady-state levels by Day 4 and were not differentially concentrated in the tissues examined. Thus, these studies characterize the testicular lesion produced by boric acid exposure and identify a decrease in basal serum testosterone levels in the absence of selective accumulation of boron in the testis.
Treinen
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National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Chapin
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D000727:Androgen-Binding Protein / Q000097:blood; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D001888:Boric Acids / Q000633:toxicity*; D001895:Boron / Q000032:analysis / Q000493:pharmacokinetics; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D011916:Rats, Inbred F344; D012708:Sertoli Cells / Q000187:drug effects / Q000378:metabolism; D013736:Testicular Neoplasms / Q000139:chemically induced* / Q000473:pathology; D013737:Testis / Q000166:cytology / Q000187:drug effects; D013739:Testosterone / Q000097:blood; D014018:Tissue Distribution
D000727:Androgen-Binding Protein; D001888:Boric Acids; D013739:Testosterone; D001895:Boron; C032688:boric acid