Characterization of Circulating Hormone Levels during Implant Treatments
The daily patterns of circulating hormones were examined in separate groups of 4-mo-old virgin rats (n = 6-10 per group) treated with P4 implants or empty implants. Consecutive blood samples (1.0 ml each) were obtained from these rats at 1000 h prior to implant placement, at 1800 h of that day, and at 1200 h on the next 2 days. Thereafter, samples were taken at 1200 h once every 2 days until the end of implant treatment. Samples were obtained by cardiac puncture under acute, light ether anesthesia. Blood was kept at 4°C overnight and then centrifuged, and serum was separated and stored at -20°C until assayed for E2, P4, LH, and FSH values by RIAs. buy ortho tri-cyclen
For comparison, samples were also obtained from cyclic control females (4-5 mo of age) at 1200 h of each day of the estrous cycle. To further reveal the patterns of gonadotropin secretion during steroid implant treatments, additional experiments were performed on separate groups of control and P4-implanted rats. Young virgin rats (n = 8 rats per group) received P4 implants as above, and 9 days after implant placement a jugular vein catheter was surgically placed as previously described. Two days later, sequential blood samples (0.4 ml each) were taken from these females through the catheter at 0800, 1100, 1400, 1700, and 2000 h. Serial blood samples were also taken from cyclic female controls on diestrous Day 1 and on proestrus (n = 5 per group). Blood was collected into a heparinized syringe and centrifuged immediately. Plasma was separated and stored at – 20°C until assayed for LH and FSH.