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Effects of Chronic Renal Failure (CRF) on the Sperm Nucleus Capacity to Fertilize Oocytes

^{1,2}N. Sofikitis, ²T. Toda, ¹I. Miyagawa, ³P. M. Zavos, ¹G. Mekras. ¹Dept of Urology, Tottori University School of Medicine, Yonago, Japan; ²Dept of Urology, The New York Hospital-Cornell University Medical Center, New York, NY; ³University of Kentucky, Lexington, KY

Objective: The detrimental effect of CRF on male fertility potential has been attributable to subnormal values of sperm concentration and motility and to decreased libido. However, there is no information whether CRF affects the sperm structures and specifically the nucleus ability to undergo the proper alterations characterizing the last events of the fertilization process. Our objective was to evaluate the influence of CRF on the physiological transformations of sperm nucleus within rabbit oocytes.

Design: Embryo development after ooplasmic injections of sperm nuclei isolated from healthy vs CRF-animals was compared.

Materials and Methods: Right nephrectomy was performed in 5 male mature rabbits (group A). Two weeks later a part of the left kidney (approximately two-thirds of the tissue) was resected. An additional group of same age male animals (n=5) underwent a two stage sham-operation (group B). Two months after the second operation, urea, creatinine, and testosterone were measured in the peripheral blood. Nuclei from caudal epididymal spermatozoa were collected by sonication of spermatozoa (one 10-seconds burst or one 40-seconds burst at 110 W power output) and subsequent density gradient centrifugation. Twenty nuclei were collected from each animal of both groups A and B. A single nucleus was injected into one mechanically stimulated oocyte. Within each group, 100 oocytes were injected. The injected oocytes were cultured at 37°C for 24 hours in a medium similar to that described by Carney and Foote (J Reprod Fertil 91:113) but it contained Dulbecco's low glucose modified Eagle's medium mixed 1:1 with RPMI 1640 medium (Gibco Co., Grand Island, NY). Oocytes were observed at various times after microinjections. An oocyte was considered activated when two polar bodies and a well-developed female pronucleus were observed.

Results: Creatinine and urea values were significantly higher in group A than in group B (Wilcoxon's test; P <|0.05). In contrast, testosterone values were significantly lower in group A (P<0.05). There were no significant differences (P>0.05; Chi-square test) in the % of activated oocytes between groups A and B (63 vs 61, respectively). The ratio 100× cleaved oocytes/activated oocytes at the end of the culture period was significantly larger (P <|0.05) in group B (68) than in group A (20). The remaining non-cleaved activated oocytes in both groups were arrested in pronuclear stage or during the process of the first cleavage. Transformation of sperm nuclei into well-developed pronuclei was observed in all of the activated oocytes in both groups A and B.

Conclusions: Our results suggest that CRF does not influence the sperm nucleus capacity to transform into male pronucleus. However, oocytes fertilized by sperm nuclei isolated from CRF-animals have a lower potential for cleavage.

Source: 1995 ASRM Meeting



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