Testicular Macrophages: Isolation, Characterization and Hormonal Responsiveness

Macrophages were isolated from rat testes with trypsin treatment and established in culture using a differential attachment technique. The cells were maintained in culture in Medium 199 at 32°C. The cells were then characterized for their ability to express traditional immunological function as well as to secrete lactate under the regulation of various hormones. The results indicate that viable cultures of macrophages were obtained since: 1) the cells stained intensely for nonspecific esterase, 2) they possessed Fc receptors on their cytoplasmic membranes, 3) they were capable of phagocytosing 3H-labeled E. coli and carbon particles, and 4) they were highly resistant to the effects of trypsin to induce detachment from the culture substrate. These cultures were not contaminated with Leydig cells or Sertoli cells since they were negative for 3β-hydroxysteroid dehydrogenase and did not secrete androgen-binding protein (ABP). Most importantly, these cells were capable of responding to follicle-stimulating hormone (FSH) in a dose-dependent manner by increasing the secretion of lactate. Maximal stimulation was observed with 1 μg FSH/ml which resulted in a 2.5-fold increase over control values. Dibutyryl cyclic AMP (dbcAMP) also caused a dose-related increase in lactate production by these cells. Luteinizing hormone (LH), insulin, testosterone or 17β-estradiol had no similar effect on lactate production by these cells. Peritoneal macrophages were not responsive to FSH or dbcAMP. These studies demonstrate that a highly enriched population of testicular macrophages can be maintained in culture and express several immunological characteristics traditionally ascribed to macrophages. In addition, these cells were capable of responding to FSH in a specific manner.