Short Communication Neurcendocrinology 17: 283-287 (1975)
Prostaglandin C2-Induced Release of Luteinizing Hormone-Releasing Factor (LRF) S. R. O je d a , J. E. W h ea to n 1 and S. M. M c C a n n 2 Department of Physiology. The University of Texas Health Science Center at Dallas. Southwestern Medical School, Dallas, Tex.
Key Words. Prostaglandin E2 • LRF release • Hypothalamus • LH release Abstract. Prostaglandin E2 (PGE,) injected into the third ventricle (3rd V) of conscious ovariectomized rats bearing a permanent jugular cannula increased the percentage of plasma samples showing detectable immunoassayable LRF levels at I, 3 and 5 min after injection. This percentage was small at 2 and 4 min. When plasma LRF and LH titers were measured in animals injected intravcntricularly with PGE, and decapitated 5 min later, both LRF and LH were significantly higher than control values of diluent-injected animals. These results indicate that PGE, is acting on the hypothalamus to induce release of LRF sufficient in magnitude to be detected by measuring this neurohormone directly in peripheral plasma.
Prostaglandins (PGs) have recently been implicated in the neural control of pituitary gonadotropin secretion [H arms et al., 1974], Among four PGs tested, PGE2 was demonstrated to be the most potent in releasing LH. The results reported herein provide direct evidence that PGE, can act at the CNS to induce release of LRF. Experiments were performed in conscious ovariectomized animals, and systemic plasma LRF levels were measured using a specific radioimmunoassay.
Received: November 19th, 1974; accepted: December 26th. 1974.
Downloaded by: Boston University 128.197.229.194 - 1/13/2019 12:50:17 PM
1 Post-doctoral research fellow of the Ford Foundation. 2 Supported by grants from NIH (AM 10073 and HD 05151), the Ford Foundation and the Texas Population Research Institute.
284
O jeda/W heaton/M c C ann
Materials and Methods Female Sprague-Dawley rats (Simonsen Laboratories, Gilroy, Calif.) weighing 230 to 270 g were used. All animals were ovariectomizcd upon arrival and housed under con trolled conditions of light (14 h on and 10 h off) and temperature (24-26 C). Purina rat chow and water were available ad libitum. Two weeks after ovariectomy a 23-gaugc stainless steel cannula was implanted into the 3rd V of each animal [H arms et al., 1974]. The same day, animals were provided with a permanent jugular cannula [H arms and O jeda, 1974]. Third ventricular injections were made 3 days following implantation. Blood samples (0.5 ml) were drawn through the jugular cannula before injection (-1 min) and 1, 2, 3, 4 and 5 min thereafter. Prostaglandin E2 (5 ftg) was injected into the 3rd V in a 5-/d volume (95% ethanol: 0.02% N a2C 0 3, 1:9) at a rate of 2.5 /d/min. Control animals were given injections of the diluent. In another experiment, PGE2 or the diluent was iniraventricularly injected as before and the animals were decapitated 5 min after the injection. Blood was collected from the trunk. Plasma LRF (in 200-/d aliquots) was measured using the procedure of N ett et al. [1973], with minor modifications. Results were expressed in terms of synthetic LRF (Beckman Instruments, Inc.). LH was measured by the procedure of N iswender et al. [1968] and expressed in terms of the NIH-LH-S1 reference preparation. The statistical significance of differences between groups was calculated using the Chi-square test ( y2) and Student’s r-test.
Results
Effect o f 3rd V PGE2 on Plasma LRF o f Decapitated Rats In the above experiments the most consistent response to 3rd V PGE2
Downloaded by: Boston University 128.197.229.194 - 1/13/2019 12:50:17 PM
Effect o f 3rd V PGE2 on Plasma LRF Titers o f Jugular-Cannulated, Ovariectomized Rats Prostaglandin E2 (5 //g in 5 /¿l) injected into the 3rd V significantly increased the number of plasma samples showing detectable LRF at I min (4 out of 8), 3 min (4 out of 8) and 5 min (6 out of 9) after its injection (p
Prostaglandin C2-Induced Release of Luteinizing Hormone-Releasing Factor (LRF) S. R. O je d a , J. E. W h ea to n 1 and S. M. M c C a n n 2 Department of Physiology. The University of Texas Health Science Center at Dallas. Southwestern Medical School, Dallas, Tex.
Key Words. Prostaglandin E2 • LRF release • Hypothalamus • LH release Abstract. Prostaglandin E2 (PGE,) injected into the third ventricle (3rd V) of conscious ovariectomized rats bearing a permanent jugular cannula increased the percentage of plasma samples showing detectable immunoassayable LRF levels at I, 3 and 5 min after injection. This percentage was small at 2 and 4 min. When plasma LRF and LH titers were measured in animals injected intravcntricularly with PGE, and decapitated 5 min later, both LRF and LH were significantly higher than control values of diluent-injected animals. These results indicate that PGE, is acting on the hypothalamus to induce release of LRF sufficient in magnitude to be detected by measuring this neurohormone directly in peripheral plasma.
Prostaglandins (PGs) have recently been implicated in the neural control of pituitary gonadotropin secretion [H arms et al., 1974], Among four PGs tested, PGE2 was demonstrated to be the most potent in releasing LH. The results reported herein provide direct evidence that PGE, can act at the CNS to induce release of LRF. Experiments were performed in conscious ovariectomized animals, and systemic plasma LRF levels were measured using a specific radioimmunoassay.
Received: November 19th, 1974; accepted: December 26th. 1974.
Downloaded by: Boston University 128.197.229.194 - 1/13/2019 12:50:17 PM
1 Post-doctoral research fellow of the Ford Foundation. 2 Supported by grants from NIH (AM 10073 and HD 05151), the Ford Foundation and the Texas Population Research Institute.
284
O jeda/W heaton/M c C ann
Materials and Methods Female Sprague-Dawley rats (Simonsen Laboratories, Gilroy, Calif.) weighing 230 to 270 g were used. All animals were ovariectomizcd upon arrival and housed under con trolled conditions of light (14 h on and 10 h off) and temperature (24-26 C). Purina rat chow and water were available ad libitum. Two weeks after ovariectomy a 23-gaugc stainless steel cannula was implanted into the 3rd V of each animal [H arms et al., 1974]. The same day, animals were provided with a permanent jugular cannula [H arms and O jeda, 1974]. Third ventricular injections were made 3 days following implantation. Blood samples (0.5 ml) were drawn through the jugular cannula before injection (-1 min) and 1, 2, 3, 4 and 5 min thereafter. Prostaglandin E2 (5 ftg) was injected into the 3rd V in a 5-/d volume (95% ethanol: 0.02% N a2C 0 3, 1:9) at a rate of 2.5 /d/min. Control animals were given injections of the diluent. In another experiment, PGE2 or the diluent was iniraventricularly injected as before and the animals were decapitated 5 min after the injection. Blood was collected from the trunk. Plasma LRF (in 200-/d aliquots) was measured using the procedure of N ett et al. [1973], with minor modifications. Results were expressed in terms of synthetic LRF (Beckman Instruments, Inc.). LH was measured by the procedure of N iswender et al. [1968] and expressed in terms of the NIH-LH-S1 reference preparation. The statistical significance of differences between groups was calculated using the Chi-square test ( y2) and Student’s r-test.
Results
Effect o f 3rd V PGE2 on Plasma LRF o f Decapitated Rats In the above experiments the most consistent response to 3rd V PGE2
Downloaded by: Boston University 128.197.229.194 - 1/13/2019 12:50:17 PM
Effect o f 3rd V PGE2 on Plasma LRF Titers o f Jugular-Cannulated, Ovariectomized Rats Prostaglandin E2 (5 //g in 5 /¿l) injected into the 3rd V significantly increased the number of plasma samples showing detectable LRF at I min (4 out of 8), 3 min (4 out of 8) and 5 min (6 out of 9) after its injection (p
