The proteins in follicular fluid from individual and pooled bovine follicles were studied by gel chromatography and quantitative immunoelectrophoresis. The mean protein concentration was 86\m=.\4% of serum; very large proteins were present in only low concentrations. A minimum of 40 individual proteins was distinguished in follicular fluid, and 15 of these proteins were quantitated. A correlation between molecular weight and follicular fluid:serum concentration ratio was found. Fluid from individual follicles differed only in the relative concentrations of small and large proteins. An exception to this was IgG which was occasionally, but never in healthy growing follicles, present in concentrations above 150% of serum. Healthy growing, preovulatory and atretic follicles had higher, and cystic follicles mostly lower, concentrations of small proteins than serum. The concentration of \g=a\2-macroglobulin in healthy growing follicles never exceeded 16% of serum. The concentration of large proteins in follicular fluid increased with increasing follicle size. Attempts to detect proteins specific to follicular fluid by immunizing rabbits with pooled follicular samples and the follicular fluid proteins not bound by anti-bovine antiserum resulted in production of antibodies against fibrinogen and its split products D + E only.

The injection of gonadotrophin (PMSG) into mice between the ages of 3 and 6 days did not alter the number of follicles that started growth, suggesting that it did not provide the stimulus to small follicles to start their development. The injection of PMSG had no influence on small oocyte atresia.

The distribution of nuclear oestrogen receptor alpha (ER-alpha) in the sex organs of fetal and newborn mice has been investigated immunohistochemically. There was no visible ER-alpha immunoreaction in the sexually undifferentiated gonads, whereas a faint immunoreaction was detected in a few cells surrounding the sex ducts, the Mullerian and Wolffian ducts. After sex differentiation, the immunoreaction of ER-alpha was observed in various cell types, with the exception of both the male and female germ cells. In the fetal ovary, immunoreaction was restricted to the surface epithelium and a few stroma cells without any preferential localization. In the testis, the number of ER-alpha-immunopositive cells, identified as Leydig and peritubular cells, increased with age. Immediately after sex differentiation, cells surrounding the sex ducts were ER-alpha-immunopositive, but no immunoreaction was detected in the epithelium in either sex. During development, the epithelium of the sex ducts attained a topographic difference in ER-alpha immunoreaction. In females, immunoreaction was detected in the epithelium of the oviduct, but not in the uterus. In males, the immunoreaction of ER-alpha was intense in the epithelium of the efferent ducts, weak in the epididymis and absent in the vas deferens. ER-alpha immunoreaction in the cells surrounding the sex duct differed between the sexes, being high in all these cells in females, but of varying intensity in males. ER-alpha may not play an important role in the development and function of ovarian cells, but may be involved in the development of Leydig and peritubular cells. Furthermore, substances that react with ER-alpha may influence the male germ cells indirectly through the ER-alpha-immunopositive peritubular cells. In addition, in both sexes, ER-alpha-immunopositive cells surrounding the sex ducts may be involved in the mediation of growth and functional differentiation of the ductal epithelium.

Mature mice, strain B6D2-F1 (an F 1 hybrid of the inbred strains, C57B1/6 and DBA/2J; Bomholtgaard, Denmark)

Levels of epidermal growth factor (EGF) and steroids were measured by radioimmunoassay in follicular fluid (FF) aspirated from 114 small antral follicles with diameters from 1 to 6 mm and in serum from 19 women undergoing Caesarean section at term. Concentrations of EGF in FF were inversely and significantly correlated to follicular size, being 4.7 +/- 0.4 (mean +/- S.E.M.) nmol/l in follicles of 1-2 mm in diameter and declining to 2.2 +/- 0.2 and 1.4 +/- 0.2 nmol/l in follicles of 3-4 mm and 5-6 mm in diameter respectively. The mean +/- S.E.M. concentration of EGF in serum (0.7 +/- 0.03 nmol/l) was significantly lower than that in FF. Levels of EGF, progesterone and oestradiol in FF were not significantly correlated to one another. In contrast to EGF, levels of progesterone and oestradiol in FF did not vary significantly with follicular diameter in these small follicles. On the basis of these results we suggest that EGF is synthesized in small human antral follicles, and that EGF stimulates granulosa cell proliferation and follicle growth up to 6 mm in diameter. Furthermore, the high intrafollicular levels of EGF may protect the small follicles against untimely effects of high levels of FSH, for instance during the mid-cycle surge of gonadotrophins. It is concluded that EGF plays an important role as an autocrine and/or paracrine regulator of development of small antral follicles in women.