The effect of gonadotrophins on the secretion rate of gonadal hormones in sheep was investigated by perfusing the ovary in situ with luteinizing hormone (lh), luteotrophic hormone (lth) and follicle stimulating hormone (fsh). The gonadotrophins were infused through the side branch of the ovarian artery and the effluent blood was collected from the utero-ovarian vein. Perfusion of the ovary on the 8th day of the oestrous cycle with lh or lth resulted in the increase of the secretion rate of progesterone within 20 to 30 min after the beginning of the perfusion; when the perfusion of the ovary was terminated the rate of progesterone secretion reverted to the original level within 20 to 30 min. Unlike lh and lth, fsh infused on the 8th day of the oestrous cycle decreased the output of progesterone. On the 15th day of oestrous cycle progesterone could not be detected in the effluent blood from the ovarian vein. At that time, perfusion of the ovaries with gonadotrophic hormones produced no effect on the secretion rate of progesterone.
Substances giving positive reaction with Barton's reagent and showing chromatographic characteristics of oestrone and oestradiol were detected in the ovarian venous blood in few animals only, and in very low concentrations. No relation was observed between the presence of these substances in the ovarian venous blood and either the phase of oestrous cycle or the type of gonadotrophin infused. Furthermore, perfusion of the ovary with fsh or lh resulted in the appearance in the ovarian venous blood of an unknown oestrogen-like substance of higher polarity than that of oestrone but lower than that of oestradiol.