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Absence of Testicular Protection by a Gonadotropin-releasing Hormone Analogue against Cyclophosphamide-induced Testicular Cytotoxicity in the Mouse¹

Departments of Experimental Radiotherapy [M. F. d. C., M. L. M.] and Endocrinology [S. N.], The University of Texas System Cancer Center, M. D. Anderson Hospital and Tumor Institute, Houston, Texas 77030

Protection of testicular integrity against damage from cyclophosphamide (CY) by simultaneous treatment with a gonadotropin-releasing hormone (GnRH) analogue was reported in BALB/c mice (L. M. Glode et al., Lancet, 1: 1132–1134, 1981). This approach has been used as the basis for clinical trials in various treatment centers (D. H. Johnson et al., Blood, 65:832–836, 1985) in an attempt to prevent iatrogenic sterility in males. This study aims at duplicating the original findings and obtaining quantitative data on spermatogonial killing by CY, and possible protection by GnRH, of differentiating and stem cell spermatogonia. Mice were treated with 23 daily injections of 0.4 µg D-leucine-6 GnRH, and with 200 mg/kg CY on Days 8, 15, and 22. Three additional groups of mice received phosphate-buffered saline and bovine serum albumin only, GnRH only, and CY only. Animals were killed at 29 days after the last injection to determine the number of late spermatids in testicular homogenates, and at 56 days for histological measurement of the ratio of elongated spermatids to Sertoli cells in the tubules. The twenty-ninth day assay was a measure of damage to differentiating spermatogonia, whose killing results in temporary sterility. The fifty-sixth day point assay assessed damage to stem spermatogonia, whose killing results in longterm or permanent sterility. Sperm counts at 29 days were identical in saline-treated control mice and GnRH-treated mice; no sperm were present in the CY-treated mice, both with and without GnRH. Thus, killing of differentiating spermatogonia by CY is not prevented by GnRH treatment. Similarly, counts of spermatids at 56 days showed no difference between saline- and GnRH-treated groups; a reduction to approximately 40% of control counts was observed equally with CY and CY plus GnRH treatments. Since GnRH treatment did not alter spermatogonial kinetics in BALB/c mice, it is not surprising that it did not protect against CY-induced damage. Thus, the mouse is not a suitable model for analyzing such effects of GnRH on spermatogenesis, and further studies in other experimental animals are needed if they are to be used as a rationale for clinical administration of GnRH to cancer patients.

¹ Supported by Grants CA-17364 and CA-06294 awarded by the National Cancer Institute.

² Present address: Department of Biology, Texas Woman's University, 1130 M. D. Anderson Boulevard, Houston, TX 77030. To whom requests for reprints should be addressed.

³ Present address: Department of Obstetrics and Gynecology, The University of Texas Medical School, Houston, TX 77030.

Received 4/ 3/86. Revised 10/23/86. Accepted 11/11/86.