Ovarian Steroid Secretion in Estrous, Mated and HCG-Treated Rabbits, Determined by Concurrent Cannulation of

Twenty one New Zealand White rabbits had both ovarian veins cannulated under nem-butal anesthesia, and blood was collected for 30 mm. Twelve rabbits were in estrus, six had received an injection of HCG between 2-6.5 h, and three had been mated 2-3 h before blood collection. The concentrations of estrone (E1), estradiol (E2) and progesterone (P) were measured by radioimmunoassay following separation on celite microcolumns. Substantial differences in concentrations of E1, E, and P between the two ovarian veins of individual estrous animals were observed in five of nine, six of 12, and two of 12 rabbits, respectively. The ratios of the steroid concentrations between the two ovarian veins ranged from 1.0-2.1 for E1, from 1.0-25.5 forE, and from 1.1-64.1 for P. After mating or HCG injection sub-stantial differences between ovaries forE,, E, and P were seen in three of six, two of nine, and eight of nine animals, respectively. Compared to the estrous animals, more rabbits showed such differences only for P and fewer rabbits differences for the other steroids. E1 and E, levels did not rise after mating or HCG injection, but by contrast P values rose significantly. A second injection of HCG given 6.5 or 7 h after an initial one caused, within the succeeding 45 mm, a further stimulation of total progestin concentration and some individual stimula