The relationship of daily sperm production with number of Sertoli cells and testicular size in adult horses: role of primitive spermatogonia.

The number of Sertoli cells is important in spermatogenesis as noted by significant correlations between the number of Sertoli cells and the number of germ cells observed as early as type B2 spermatogonia in the horse. However, the stage within spermatocytogenesis at which these relationships first occur is unclear. The relationships between the number of Sertoli cells and parenchymal weight and the number of germ cells during the mitosis of spermatogenesis were determined in 184 adult horses to identify the developmental stage (that is, the earliest germ cell) at which significant relationships are established. The total numbers of all types of A spermatogonia and of specific subtypes (A1, A2, A3, B1 or B2) of spermatogonia were correlated with the number of Sertoli cells and with parenchymal weight. The number of each cell type was calculated using stereology. The number of Sertoli cells was correlated (P < 0.01) with parenchymal weight (r = 0.85) and with daily sperm production (r = 0.83), and parenchymal weight was correlated (P < 0.01) with daily sperm production (r = 0.89). The number of Sertoli cells was correlated (P < 0.01) with the number of type A (r = 0.81) and A1 (r = 0.74) spermatogonia. Parenchymal weight was correlated with the number of type A (r = 0.80) spermatogonia and with the number of A1 (r = 0.67) spermatogonia.(ABSTRACT TRUNCATED AT 250 WORDS)