Morphological and functional features of ovine follicles in perifusion with pulsatile hormone delivery

Large follicles were obtained from sheep ovaries during the follicular phase, dissected and incubated for 24 h in a perifusion system. Continuous flow of B2 medium gassed with O2 and CO2 and supplemented with FSH/LH pulses every other hour enabled us to measure the steroid secretion rates of each follicle. At the end of the perifusion, the follicles were processed for histological examination. It was demonstrated that 70% of the follicles were healthy after 24 h of perifusion. This was associated with a high secretion rate of oestradiol compared to atretic follicles. In contrast testosterone and progesterone secretion rates were similar in healthy and atretic follicles. In both healthy and atretic follicles, repeated gonadotrophin pulses produced increases in steroid production. Such a perifusion system might be a valuable tool to study between and within-follicle interactions to get new insights in paracrine and autocrine regulations in the ovary.