Effect of metabolic stressors on survival and growth of in vitro cultured ovine preantral follicles and enclosed oocytes

The present study was undertaken to study the effect of metabolic stressors like elevated levels of ammonia, urea, Non-esterified fatty acid (NEFA) and eta-hydroxybutyric acid (BHB) on preantral follicle growth, survival, growth rates of oocytes enclosed in preantral follicles (PFs), maturation rates of oocytes recovered from cultured follicles, hormone production (estrogen and progesterone), reactive oxygen species (ROS) as well as superoxide dismutase (SOD) activity. Small pre-antral follicles (SPFs, 100 -250 mu m) and large pre-antral follicles (LPFs, 250-450 mu m) were isolated from slaughterhouse ovaries by a mechanical cum enzymatic method. SPFs and LPFs were cultured in vitro for 14 and 7 days respectively and examined for their growth, survival and growth rates of enclosed oocytes in PFs exposed with different concentration of ammonia (0,100, 150, 200, 250, 300 and 400 mu m), urea (0, 4, 4.5, 5, 5.5,6, 7 and 8 mM), NEFA [Basal NEFA (70 mu M): stearic acid, SA (10 mu M)+Palmitic acid, PA(20 mu M)+oleic acid, OA(40 mu M), b) Medium combo (140 mu M): SA (20 mu M)+ PA(40 mu M)+ OA(80 mu M), c) High combo (210 mu M): SA (30 mu M)+PA(60 mu M)+OA(120 mu M), d) Very high Combo (280 mu M): SA(40 mu M)+PA(80 mu M)+ OA(160 mu M)] and BHB (0, 0.5, 0.75, and 1 mu M). Results indicated that ammonia, urea, NEFA and BHB caused inhibition of survival and growth of in vitro cultured ovine PFs and enclosed oocytes at the levels of 300 mu M, 8 mM, high combo level of NEFA and 0.75 mu M respectively. Our study may contribute to the identification of the mechanisms involved in decline of fertility due to metabolic and nutritional stress in ruminants. (C) 2017 Elsevier Inc. All rights reserved.