The present study examined the influences of physical and hormonal microenvironment on in vitro growth and steroidogenesis of dog follicles. Follicles were enzymatically-isolated and individually-encapsulated in 0.5% (w/v; n = 17) or 1.5% (n = 10) alginate and cultured with 0.5 IU/ml equine chorionic gonadotropin for 192 h. In a separate experiment, follicles were encapsulated in 0.5% alginate and cultured with 0 (n = 22), 1 (n= 23), 10 (n = 20) or 100 (n = 21) {micro}g/ml FSH for 240 h. Follicle diameter and steroid production were assessed every 48 h in both studies. Follicles encapsulated in the 0.5% alginate grew faster (P 0.05) across FSH dosages. However, P4 increased (P < 0.05) as culture progressed and with increasing FSH concentration. Results demonstrate that dog follicles cultured in alginate retain structural integrity, grow in size and are hormonally active. Lower alginate and increasing FSH concentrations promote in vitro follicle growth. However, the absence of an E2 rise in follicles cultured in FSH alone suggests the need for luteinizing hormone supplementation to support thecal cell differentiation and granulosa cell function.
