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Perfluorochemicals are compounds in which all the hydrogen atoms have been replaced by fluorine atoms. Because of their high capacity to dissolve oxygen, perfluorochemicals have been used as artificial oxygen carriers in organ perfusions. Previous experiments suggested that perfluorochemicals failed to support testosterone secretion by rat testes. We hypothesized that fluoride ions in the perfusion medium may have been the toxic factor. We tested this hypothesis by adding sodium fluoride to perfusion medium with red blood cells as oxygen carriers. Rat testes were perfused (20 ml/h) at 32*C with an artificial medium containing LH (100 ng/ml), 0.2% glucose, 3% KRB-BSA, 25% washed bovine erthrocytes, and sodium fluoride. Testicular venous effluent was collected after 3 h of perfusion and analyzed for testosterone using a radioimmunoassay.

Fluoride Concentration (uM)	Testosterone Secretion (ng/h-g testis)
		n
0	2543 + 214	18
100-200	2387 + 249	10
250-450	520 + 100	6
1050	22 + 1	3

The results (see above) provide unequivocal evidence that 250 uM fluoride inhibits testosterone secretion by rat testes perfused in vitro. Previous investigators have reported that 5-10 mM fluoride stimulates adenylate cyclase, inhibits metabolic reactions, and inhbits testosterone biosynthesis. The present observation of deleterious effects by 250 uM fluoride (5 ppm) emphasizes the sensitivity of steroidogenesis to fluoride.

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