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Suppression of Postnatal Changes in Spermatogenesis, Size, and Nucleic Acid Content of Rat Testis by Chronic Administration of Isoproterenol

Summary Chronic administration of large doses of the catecholamine isoprotere-nol to immature rats suppressed the postnatal changes in testis size and spermatogene-sis that normally occur. Nucleic acid content (total DNA and RNA) was reduced from controls at each weekly interval examined. With increasing age there is normally a decrease in number of spermatogonia observed in seminiferous tubules, and at 28 days of age, 56% remain, but by 50 days, only 25% remain. This change is altered by treatment with isoproterenol, and while the number at 28 days is the same, the number remaining at 50 days had decreased to a much smaller extent so that 44% remained. Isoproterenol thus greatly inhibited sperma-togenesis, and the number of cells in meiotic stages and number of mature sperm formed were also greatly decreased from control. While mature sperm were first found in untreated and ISO-treated animals at the same age (42 days), the number in ISO-treated rats was only one-third that of controls. This same order of reduction remained evident at 50 days also. Treatment of adults with isoproterenol for 7 days did not alter nucleic acid content, course of spermatogenesis, or production of mature sperm. This work was supported in part by National Institutes of Health Grant DE 02110. The authors wish to thank Dr. A. Siegel, Clinical Pathology, University of Alabama Medical Center, for determination of testosterone levels in serum.