Analysis of the variations of follicular fluid composition during follicular growth and maturation in the mare using proton nuclear magnetic resonance (1H NMR)

Follicular development and ovulatory processes in mammals involve local biochemical changes as a result of substantial modifications in cellular metabolism, the most well known of which is steroid variation. In the present study, the intrafollicular variation of several other components was studied using proton nuclear magnetic resonance (H-1 NMR). This approach made it possible to demonstrate that the intrafollicular biochemical content changes during follicular growth and maturation. Follicular fluid was aspirated by ovarian puncture of the dominant follicle at various physiological stages of its development: early dominant, late dominant and preovulatory. Serum samples were collected during each puncture session. H-1 NMR was used to evaluate intrafollicular and circulating glycoconjugates (sugar chains and N-acetyl groups), lipoproteins (CH3 and CH2 groups), glucose metabolites (trimethylamines, acetate and lactate), amino acids (glutamine/glutamate and alanine), creatine/creatinine and polyamines. Follicular fluids were assayed by radioimmunoassay for oestradiol and progesterone contents. The intrafollicular contents of alanine and lipoproteins (CH3 groups) decreased in the dominant follicle during growth, whereas concentrations of progesterone and oestradiol increased significantly. After injection of gonadotrophin to induce ovulation, follicular maturation was characterized by a decrease in glycoconjugates (sugar chains), trimethylamines and acetate, a decrease in oestradiol concentration, and a further increase in CH3 groups of lipoproteins and progesterone. The results from the present study showed a clear correlation between the intrafollicular content of alanine and that of oestradiol. A correlation between progesterone and glycoconjugates (sugar chains) was also observed. Therefore, H-1 NMR was shown to be effective for studying specific changes in the biochemical composition of the follicular fluid that occur during follicular development. For the first time, the variation of several compounds (glycoconjugates, lipoproteins, glucose metabolites, amino acids and polyamines) in relation to growth and maturation was demonstrated. Some of these changes could be of crucial importance for follicular maturation and ovulation as well as for oocyte maturation and further fertilization.