EFFECT OF FOLLICLE SIZE AND QUALITY ON THE ABILITY OF FOLLICULAR-FLUID TO SUPPORT CYTOPLASMIC MATURATION OF BOVINE OOCYTES

Recent studies have shown that the developmental capacity of in vitro- matured oocytes is affected by the origin of follicular fluid (FF) sup plemented to the maturation medium. The aims of this study were (1) to determine if follicle size and quality would influence the capacity o f FF to support bovine oocyte maturation and (2) to determine if fetal calf serum (FCS) and FF had an additive effect when added together to the maturation medium. Follicular fluid collected from 108 follicles was classified according to size (<6, 6-8, >8 mm in diameter) and qual ity (healthy, early atretic, and atretic). Quality, first determined b y mitosis/pycnosis ratios in granulosa cell smears, was subsequently c onfirmed by insulin-like growth factor binding protein (IGFBP) pattern s and estradiol concentrations. While most small- or medium-sized foll icles showed some atresia (88% and 67%, respectively), fewer of the la rge follicles were atretic (30%). In experiment 1 bovine oocytes (n = 2,152) were matured either in TCM199 alone, with 10% FCS, or with 10% FF from the following follicle types: small healthy (SH); small early atretic (SEA); small atretic (SA); medium healthy (MH); medium early a tretic (MEA); medium atretic (MA); large healthy (LH); large early atr etic (LEA); and large atretic (LA). Following IVM, oocytes were fertil ized and subsequently cultured in synthetic oviduct fluid (SOF). Day 8 blastocyst yields were 23% in TCM199 alone; 37% in TCM199 plus FCS; a nd, in medium supplemented with FF, SH, 36%; MH, 32%; LH, 30%; SEA, 21 %; MEA, 26%; LEA, 28%; SA, 32%; MA 33%; and LA, 38%. All FF from healt hy or atretic follicles resulted in significantly improved blastocyst yields compared to M199 alone (P < 0.05). However, FF from early atret ic follicles irrespective of size did not yield a significant improvem ent. In experiment 2 we examined the effect of addition of FF-LH and s erum together to the maturation medium, In terms of blastocyst yield, no additional benefit was observed when TCM199 was supplemented with 1 0% FCS + 10% FF (33%) compared to 10% FCS or FF alone (35% and 30%, re spectively). The efficacy of FF as a supplement to the maturation medi um to improve cytoplasmic maturation appears to vary with follicle qua lity but not size. However, in general, the addition of 10% FF or FCS to the maturation media resulted in a similar blastocyst yield with no additional improvement when media was supplemented with both FCS and FF. (C) 1996 Wiley-Liss, Inc.