FUNCTIONAL ASSESSMENT OF AUTOTRANSPLANTED ENDOCRINE ORGANS

Abstract

ABSTRACT Autotransplants of the adrenal gland and of the ovary have been extensively used to study basal secretion and mechanisms of control of steroid secretions by these organs. The validity of the use of such preparations for this purpose is critically examined in this paper. Autotransplantation did not materially affect the normal histological architecture of the glands. The adrenal became re-innervated and re-connected to the lymphatic system. Sheep with their remaining adrenal gland transplanted to the neck not only survived for many years but also could support normal pregnancy. The blood flow through the transplants was somewhat greater than that from the organs in situ. This was shown to be due to (a) absence of acute vasoconstriction due to recent surgery, (b) some degree of admixture with peripheral blood, (c) compensatory hypertrophy. Steroid secretion from the autotransplants was similar to that from in situ glands and could be increased by specific stimuli. Biosynthetic transformations, with simultaneous measurements of hormone secretion rates, can be studied under controlled conditions. Cyclic behaviour was disturbed when the ovary alone was transplanted to the neck, but this was restored when the ovary and the uterus were transplanted together to a cervical site. Impairment of cyclicity was shown to result from the separation of the ovary from the uterus. The uterus was shown to affect luteal function by secreting the prostaglandin (PG) F2α. PGF2α gained access to the ovarian circulation by a countercurrent mechanism which was demonstrated to be quantitatively competent to cause luteolysis in the normal animal. The minimum infusion rate of PGF2α into the uterine vein of sheep on day 7 of the cycle which would cause luteolysis was about 20 μg/h. This is similar to the observed rate of PGF2α secretion in the uterine vein of ewes at the time of luteolysis. Hence PGF2α can be regarded as »the« luteolytic hormone in the sheep, and the ovine uterus as an endocrine organ.