EFFECTS OF THE LUTEINIZING HORMONE ON BLOOD FLOW IN THE FOLLICULAR RABBIT OVARY, AS MEASURED BY RADIOACTIVE MICROSPHERES

Abstract

Previous reports on the ovarian hyperaemia induced by luteinizing hormone (LH) and human chorionic gonadotrophin (HCG) were based largely on direct observations and semi-quantitative methods. An accurate quantitation of ovarian blood flow changes would contribute to a better understanding of the mechanisms for and physiological significance of this rapid effect of the hormones. In the present study ovarian blood flow was determined before and after a single intravenous injection of LH to anaesthetized, post-pubertal virgin rabbits, using 15 ± 5 μm microspheres, labelled with Ytterbium-169 and Scandium-46. Two min after administration of 100 μg of bovine LH a significant decrease in ovarian vascular resistance was noted. The response was even more pronounced after 20 min. Pre-treatment of the animals with an adrenergic β-receptor blocker did not diminish the LH induced ovarian vasodilatation. The vasodilatation appeared specific to the ovary, as indicated by simultaneous determinations of blood flow and vascular resistance in other organs and tissues. The microsphere technique is considered to be the method of choice for future studies of the mechanism of the LH induced ovarian vasodilatation.