ETHNIC-DIFFERENCES IN TESTICULAR STRUCTURE AND SPERMATOGENIC POTENTIAL MAY PREDISPOSE TESTES OF ASIAN MEN TO A HEIGHTENED SENSITIVITY TO STEROIDAL CONTRACEPTIVES

Spermatogenesis in Asian men appears to be more susceptible to suppres sion by steroidal contraceptives administered in clinical trials than spermatogenesis in Caucasian men. The objective of this study was to d etermine whether ethnic differences exist in testicular structure and spermatogenic potential that might predispose Asians to a high sensiti vity to steroidal contraceptives. Testes from 12 Chinese men were comp ared to those from 8 Hispanic men and 12 non-Hispanic Caucasian men of ages 29 +/- 3, 30 +/- 2, and 29 +/- 3 years, respectively. Testes wer e fixed by vascular perfusion with glutaraldehyde, further fixed in os mium, embedded in Epon, and evaluated by stereology using 0.5-mu m sec tions stained with toluidine blue. Homogenates of fixed testes were ev aluated for the number of Sertoli cells and the daily sperm production based on pachytene primary spermatocytes (PDSP) or spermatids with sp herical nuclei (DSP). Paired parenchymal weight was less (P < 0.05) in Chinese men than in Hispanic or Caucasian men. The PDSP per gram of p arenchyma was lower (P < 0.05) and the DSP per gram tended to be lower in Chinese men than in other groups. The histologic appearance, volum e density, and length per man of seminiferous tubules were the same am ong the ethnic groups however, the diameter of seminiferous tubules wa s less (P < 0.05) In Chinese than in Hispanic or Caucasian men. The PD SP per man and the DSP per man were lower (P < 0.05) in Chinese than i n Hispanic or Caucasian men. The number of Sertoli cells per gram was higher (P < 0.05) in Chinese or Caucasian men than in Hispanic men, bu t the number of Sertoli cells per man was lower (P < 0.05) in Chinese men than in Hispanic or Caucasian men. Sertoli cell function, measured as the number of germ cells accommodated by a single Sertoli cell, wa s lower (P < 0.05) in Chinese men than in Caucasian men. The volume de nsity of Leydig cell cytoplasm was greatest (P < 0.05) in Chinese men, but the number of Leydig cells was similar among the ethnic groups. H ence, smaller testes coupled with reduced Sertoli cell number and func tion and reduced daily sperm production could predispose Asian men to have a heightened negative response of testes to steroidal contracepti ves, as compared to Caucasian men. Dampening (by exogenous androgens) of any physiological benefit to spermatogenesis that a high volume den sity of Leydig cell cytoplasm may bestow on the human testis (that Asi an men may have evolved to require) would exacerbate ethnic difference s in the spermatogenic response to hormonal contraceptives.