Demonstration of luteinizing hormone releasing factor in hypophysial portal blood of pro-oestrous & hypophysectomized rats.

1. A method for the routine collection of hypophysial portal blood from rats under direct vision has been described.2. This method has been used to obtain portal blood from adult female rats in pro-oestrus and adult female rats which had been hypophysectomized at least 14 days before collection.3. The pooled plasma from this blood was assayed for activity, resembling that of luteinizing hormone releasing factor (LRF), by the ovarian ascorbic acid depletion method.4. The portal plasma from both groups of donor animals exhibited significant activity when compared to peripheral plasma controls.5. It is concluded that the ovarian ascorbic acid depleting activity of portal plasma was due to LRF.6. The possibility that some of the activity exhibited by portal plasma from pro-oestrous rats was due to contamination of the samples by LH containing backflow blood from pituitary sinusoids is discussed.7. The possibility that the ovarian ascorbic acid depleting activity of the hypophysial portal plasma was due to either vasopressin or a nonspecific factor has been excluded.