Comparison of the cellular composition and steroidogenic properties of preparations of interstitial cells isolated from immature and mature rat testis.

The morphological and steroidogenic properties of preparations of interstitial cells isolated by collagenase treatment from testes of immature and mature rats have been compared. After additional purification on a Ficoll gradient, 80% of cells from mature rat testes were found to be Leydig cells; 20% were macrophages. Forty to sixty per cent of collagenase-dispersed cells isolated from immature rats were Leydig cells, 37% were mesenchymal cells and there were no macrophages. A preparation in which 90% cells were Leydig cells could be obtained from immature testes after further purification by centrifugation through a Percoll gradient. The distribution of steroidogenic enzymes through the gradient corresponded to the distribution of LH-dependent steroid production. The results indicate that the steroidogenic activity per Leydig cell from mature rats is fourfold greater than the activity in immature rat Leydig cells in control incubations or after stimulation with LH, dibutyryl cyclic AMP or in the presence of 22R-hydroxycholesterol.