Intrafollicular application of ACTH in dairy cows delay ovulation without changes in follicular blood Flow

BELOTTI, E. M.; ETCHEVERS, L.; FILIPPA, E.; AMWEG, A.; ORMAECHEA, N.; CHIARAVIGLIO, J.; NOTARO, U.; ORTEGA, H. H.; SALVETTI, N. R.

Congreso; LXVII Reunión anual de la Sociedad Argentina de Investigación Clínica (SAIC); 2022

Dairy cattle are subjected to stressful situations some of which canbe associated to reproductive disruptions. In the ovary, follicles receiveblood supply through a complex network of blood vessels.Functional and structural changes occur mainly in microvasculatureof the follicular-luteal complex and have important roles in folliculogenesisand ovulation. Under stressful conditions, the microenvironmentof the ovary is modified, affecting normal follicular dynamic.Previous studies have determined that adrenocorticotropic hormone(ACTH) is able to stimulate cortisol secretion in follicular wall in vitroand, additionally follicular cells express MC2R receptors. The aimof this study was to evaluate time to ovulation and hemodynamicchanges in the ovulatory follicles after intrafollicular ACTH administration.Multiparous Holstein x Jersey cows without reproductivedisease checked by US were included on the study. Estrous cycleswere synchronized by G6G protocol. Then, ACTH (10IU in 0.1mL)was administered two days before expected day of ovulation, byUS-guided intrafollicular injection (AG; N=5). Control group (CG;N=4) received 0.1 mL of physiological solution. Power Doppler USwas performed once a day during proestrus until ovulation. Follicularblood flow was quantified by Image J Software and a repeated-measures analysis was performed using the Generalized LinearModel approach to evaluate follicular blood flow. No differenceswere observed on follicular blood flow, although a delay on ovulationtime (days) was observed on treated cows (CG=19.75 +/- 0.95 vsAG=22.5 +/- 3.1). Considering ACTH receptors on follicular cells,it is likely that the delay in ovulation could be related to effects ofthis hormone at local level. More studies for confirmation of this delayedovulation and changes at molecular level must be carried out,however it can be proposed that these results are consistent withpossible local effects of ACTH on mechanisms involved in ovulation.