Characterization of persistent follicles induced by prolonged treatment with progesterone in dairy cows: An experimental model for the study of ovarian follicular cysts.

DIAZ, PU; STANGAFERRO, ML; GAREIS NC; SILVIA WJ; MATILLER V; SALVETTI NR; REY F; BARBERIS F; CATTANEO L; ORTEGA HH

THERIOGENOLOGY

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2015 vol. 84 p. 1149 - 1160

0093-691X

Cystic ovarian disease (COD) is a major factorcontributing to poor reproductive efficiency of lactating dairy cows. Theobjective of the present study was to analyze the endocrine profile, growthdynamics and histological characteristics of persistent ovarian follicles/cystsdeveloping in response to long-term administration of intermediate levels of progesterone.To this end, after synchronization of cows, a low dose of progesterone wasadministered for 5, 10 and 15 days after the expected day of ovulation intreated cows (groups P5, P10 and P15 respectively), using an intravaginalprogesterone-releasing device. A significant increase in diameter was detected on day11 of progesterone treatment and thereafter (p<0.05) and at day 15 ofpersistence the diameter of the persistent follicle reached a mean of 23 +/-0.6 mm. Microscopically the persistent follicles had a complete granulosa, anintensely vascularized theca interna and a collagenous theca externa layer. Temporalchanges in the serum concentrations of estradiol, progesterone and FSH were detected(effects of time, p<0.01). Progesterone treatment completely inhibited theLH preovulatory surge in treated cows and affected the basal concentration ofLH. The pulse frequency remained high at 5 and 10 days of persistence anddeclined (p<0.05) after 15 days of persistence. The LH pulse concentrationand pulse amplitude had a significantly reduction (p<0.05) during follicularpersistence. Changes in the serum levels of estradiol, progesterone,17-hydroxyprogesterone, and testosterone in serum and follicular fluid were alsoobserved. In serum, estradiol increased gradually from proestrus to day 10 offollicular persistence (p<0.05), progesterone show an increase (p<0.05)at day 5 of follicular persistence, 17-hydroxyprogesterone showed a significantdecrease at 5 days of follicular persistence in relation to proestrus andtestosterone showed a significant increase (p<0.05) from proestrus and day 5of persistence through day 15 of follicular persistence. Correlation betweenserum and follicular fluid steroid concentrations was significant fortestosterone (p<0.0001) and not significant for estradiol and progesterone. These findings indicate that ovarian cysts in COD aresimilar in many ways to the persistent follicles induced by progesterone, withan analogous hormonal and morphological context, thus confirming a local role ofsub-luteal levels of progesterone in COD pathogenesis and in the regulatorymechanisms of the ovarian function.