The effect of 6-aminonicotinamide on testicular development in the rat.

6-Aminonicotinamide (6-AN), a niacin antagonist, was administered sc to pregnant female (1.0, 3.0, or 6.0 mg 6-AN/kg body weight) and neonatal male (1.5, 3.0, 6.0 or 12.0 mg 6-AN/kg body weight) Sprague-Dawley rats on the 15th, 17th and 19th days of gestation or the 5th, 7th and 9th days of life, respectively, to determine the effects of the antimetabolite on testicular morphology and development. In prenatal males, microscopic alterations were present in testes of fetuses from females treated with 6.0 mg 6-AN/kg and consisted of necrosis and loss of gonocytes, and vacuolation of interstitial cells. Histologic changes in testes of neonatal rats treated with 3.0, 6.0 or 12.0 mg 6-AN/kg were qualitatively similar with necrosis and loss of spermatogonia and supporting cells, and increased cross-sectional areas of affected tubules. Quantitation of the number of nuclei/cm2 of seminiferous tubule indicated 6-AN caused a significant reduction in the numbers of supporting cells and spermatogonia/tubular cross-section.