Luteinizing hormone and ovarian activity in response tokisspeptin-10 and its association with IGF-1 and leptin inprepubertal heifers

Abstract

We evaluated the  effect of kisspeptin-10  (Kiss-10) administered repeatedly  on  the release  of  LH  and ovarian  activityin  prepubertal  heifers.  We  also  assessed  the  association  of  serum  IGF-1  and  leptin  with  these  effects.  FourteenHolstein  or  Brown  Swiss  by  Zebu  female  calves  (11.2  ±  0.2  mo  old,  187.4  ±  6.3  kg)  were  randomly  assigned  toreceive every  2 h for three days an i.v. application of Kiss-10 (Kisspeptin-10; 5 μg/kg of body weight, n= 7) or salinesolution (control, n= 7).  Blood was  collected every 15 min for  0-6, 24-30 and  72-78  h, and every  2 h until 84 h. Eachapplication of Kiss-10 was followed by an increase of LH whose magnitude (area under the curve) decreased (P<0.05)over time. Kiss-10 induced a preovulatory surge of LH and corpus luteum formation in 28.5 % of the calves. Ovulatingcalves  had  the  highest  (P<0.05)  serum  concentrations  of  IGF-1  and  the  lowest  (P<0.05)  leptin.  During  63  post-treatment days, no changes  were detected in follicular waves attributable to treatments (P>0.05) and heifers did notshow  cyclic  ovarian  activity.  The  conclusion  is  that  Kiss-10  given  repeatedly  to  prepubertal  heifers  is  sufficient  toevoke  consistent  increases  of  LH,  to  induce  ovulation  and  luteal  activity  in  animals  with  high  IGF-1  and  low  leptinin  peripheral  blood  but  it  is  insufficient  to  establish  regular  estrous  cyclicity.