Superfusion of hemipituitaries with hypophysial portal blood: secretion of LRF in castrated and diestrous rats

A technique was developed for superfusion of rat hemipituitaries with hypophysial portal blood. One hemipituitary was placed in a special chamber and superfused with portal blood at a rate of 7 ul/min for 80 min. The contralateral hemipituitary was superfused simultaneously with blood from a femoral artery. The effluent blood was recollected at the end of the experiment in 40 fractions (each equivalent to 2 min of superfusion) and assayed for LH by RIA. There was no difference in LH output by the two hemipituitaries when one was superfused with blood from the left femoral artery and the other with blood from the right femoral artery. Hemipituitaries superfused with portal blood from castrated female rats secreted LH 2 to 3 times faster than did the contralateral hemipituitaries superfused with arterial blood. There was no difference in the LH output by hemipituitaries superfused with portal or arterial blood from diestrous rats. Endogenous LH in the blood entering the chamber constituted no more than 3% of the LH in the blood leaving the chamber. The data indicate that in the castrated rat there is an increased concentration of LRF in hypophysial portal blood. During the diestrous stage of the ovulatory cycle, there is little LRF activity in portal blood. Some LRF activity may be present in arterial blood of castrated rats.