Search for Arteriovenous Shunts in the Genital Tract of the Pseudopregnant Rabbit

Abstract

Introduction. The blood flow within an endocrine gland plays an essential role in the control of its physiological activities. Some of the complex hemodynamics changes of the ovary have been described during the preovulatory period ( 1 ), pseudo-pregnancy ( 2 , 3 ), and pregnancy ( 4 ). The mechanisms that regulate these changes are not clear, but hormones ( 5 , 6 ) and amines have been implicated in circulatory control ( 7 ). The luteolytic process is characterized by a remarkable decline in ovarian blood flow ( 4 ) and progesterone secretion ( 8 ). The drop in blood flow to the corpus luteum has been attributed to the presence of arteriovenous shunts which would divert blood flow from the corpus luteum ( 9 ). In this report we present evidence indicating that, in the pseudopregnant rabbit, no demonstrable arteriovenous shunts are found in the ovary.

Materials and methods. Mature New Zealand White rabbits, 3-4 kg in weight, were kept in individual cages for 3 weeks prior to use. Blood flow determinations were carried out 6, 12, and 18 days after iv administration of 100 IU of hCG. Analgesia was induced with Innovar (0.2 mg/kg) administered intramuscularly. Both femoral arteries were catheterized with a poly vinyl tube (PE. 60, Clay-Adams, N.J.). The right catheter was advanced until its tip was about 3 cm below the diaphragm. This catheter was used for the administration of radioactive microspheres. The left femoral catheter was advanced about 2 cm into the artery and connected to a Harvard pump. Each animal received approximately 1,500,000 micro-spheres, 15 ± 5-μM diameter, labeled with St⁸⁵ and 400,000 microspheres, 50 ± 5-μm diameter, labeled with CE¹⁴¹ (3M Company, St. Paul, Minn.). The spheres were suspended in 0.8 ml of 10% dextran in physiologic saline, mixed well, and injected immediately through the right femoral catheter.