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446. Effect of prostaglandin F2α, on the ovarian ascorbic acid and plasma progesterone levels of immature pseudopregnant rats
402
Abstracts
We have previously observed that in human placentas perfused in vitro, HCG, LH and CAMP have a stimulating action on aromization as well as on glycogenolysis. Prostaglandins FZ2, E, and chiefly E, induce also a significant increase in oestrogen production from testosterone. CAMP concentration in placental fragments taken during the experiments and assayed by a binding method was constant during blank experiments, but increases significantly 5 min after addition of HCG, LH and prostaglandins. The intensity and the duration of the stimulatory action of prostaglandins is more important than the action of gonadotropins, both on aromatization and on CAMP level. The glycogen phosphorylase enzyme system is also activated by HCG, LH. prostaglandins and CAMP. These findings confirm and extend our previous hypothesis of a mechanism of action of HCG on placental steroidogenesis mediated by CAMP. and suggest the possibility that prostaglandins may play a second messenger role in this action. Furthermore, incubations of full-term placental slices have shown efficient fixation of I,,, HCG, the specificity of which is under investigation.
13B. Prostaglandins in steroid biosynthesis 445. Effect of gonadotrophins on prostaglandin production by the rat ovary BAUMINGER,S. and LINDNER, H. R., Department of Biodynamics, The Weizmann Institute of Science, Rehovot. Israel The possibility of prostaglandin involvement in the process of follicular rupture was tested by determining prostaglandin levels. as well as prostaglandin synthetase activity in rat ovaries. Prostaglandin E2 levels were low (15-30 pg/mg tissue) in rat ovaries during the whole oestrous cycle, except on the evening of proestrus, after the peak of LH secretion. Prostaglandin EZ content at this period was increased 8-10 fold. Injection ofindomethacin, which was shown to prevent ovulation, lowered prostaglandin E, content of the ovaries. Injection of luteinizing hormone (10 pg/rat) on the morning of proestrus increased the level of PGE, in 4 h, but not at 2 h, to the same extent as seen in nontreated female rats at the evening of proestrus. Here again, indomethacin was an effective inhibitor of prostaglandin formation. FSH (100 pg/rat) wasequally effective in increasing prostaglandin E2 content. The activity of the enzyme system synthesizing prostaglandin was not significantly altered in the LH and FSH treated rats. Thus the possibility exists that the rise in prostaglandin content after the LH surge may be due to increased availability of the precursor arachidonic acid. perhaps resulting from stimulation of phospholipase.
446. Effect of prostaglandin F2. on the ovarian ascorbic acid and plasma progesterone levels of immature pseudopregnant rats SUNDARAM.K., The Population Council. The Rockefeller University, New York, 10021, U.S.A. The ovarian ascorbic acid depletion (OAAD) test has widely been used as a specific bioassay for LH and LH-like substances. LH is considered luteotropic while prostaglandin F,, (PG) is considered luteolytic. In this study the effect of PG on the OAAD test and plasma progesterone (P) levels (RIA) has been examined. Immature rats were prepared
for the OAAD test according to the method of Parlou. LH (NIH-LH-Sl8), 4.Opg i.v.. decreased the OAA to 56”,, and increased the P to 133”,, of control values. PC; (2OOpg SC) decreased the OAA to 78”,, and the P to 52”,,. Concomitant injection of LH overcame the effect of PG on the P level which increased to 124”,, but further depressed OAA to 541;. PG (IOO~~g/uterine horn) depressed the P to increased P to 21”:. and OAA to 56”:. LH. concomitantly, 110”” but further depressed OAA to 3c)“,,. The greater effectiveness of PG by the intrauterine route compared to the SCroute suggests a direct effect on the ovary. These data indicate that: (I) The OAAD test can be influenced by nongonadotropic substances and (7) that the changes in OAA levels do not always reflect the steroidogenic activity of the corpora lutea. (Supported by grant no. PO1 HD 05 71-UI from NICHHD). 447. Effects of prostaglandin PgF2a on progesterone and estrogen secretion by rabbit granulosa cells luteinized in tissue culture BATTA, S. K. and NICOSIA.S. V.. Dept. of ObstetricsGynaecology. University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19174, U.S.A. An in vitro corpus luteum system (Nicosia. S. V.. Fer/i/ Steril 23, 791. 1972) was used to study the influence of PgF2z on luteal steroidogenesis. Rabbit parietal granulosa cells and cumuli oophorii luteiniled during a 4 day culture period in X5”,, M199. 15”,, heat-inactivated serum. and antibiotics (C). following which they were fed for additIonal 4 days with medium C alone or enriched with PgF2r. IO0 (S) or 500 (L) pg/ml. No significant changes in the morpholog> ofluteinized granulosa cells were noted with PgF2;(. Oocq teh remained morphologically well preserved during the first 3 days of explantation. after which parthenogenetic cleuvugcs were seen (33”,,) both in C and PgF2r cultures. Radioimmunoassayable progesterone (pg!ml ; means i SD) decreased from the fourth (D4) to the eighth (D8) day. more significantly (p ~0.1) in PgFZx (D4: S-1620*960. L-1080 +780; D8: S-930+_400, L-490*330) than in C cultures (D4: 14OOi 1080. D8: 1200+970). In contrast, preliminar!, estrogen values indicated an increase (from 56 to 192 pg, ml) in PgFZti-S and insignificant changes in C and PgFZr-L cultures. Under such experimental conditions and doses, these results suggest that PgF2r may exert a direct influence on the steroidopoietic characteristics of luteinized granulosa cells without obviously affecting their morphology. 448. Hormonal changes occurring in cattle around normal oestrus and following administration of several luteolytic prostaglandins NANCARROW.C. D.. RADFORL).H. M., CO&NELL.P. J. and MATTNER, P. E.. C.S.I.R.O.. Division of Animal Physiology, Prospect, N.S.W.. Australia, 2148 Assessment of the effectiveness of synthetic and natural11 occurring luteolytic prostaglandins requires demonstration of both luteolysis, and the absence of abnormal changes associated with subsequent oestrus and ovulation. Prostaglandins were administered to 119 cows between days 6-16 of their oestrous cycle and blood collected at ?4h intervals. Plasma progesterone concentrations (ng,‘ml, . mean f SE.) at 0, 24 and 48 h in cows exhibiting oestrus within 5 davs (n = 113) were 743 + 0.21. I.27 + 0.05 and 0.06 + 0.03: while in cows exhibiting oestrus after 6 days (n = 6) they were 6.52 i 0.61. 2.38+ 0.62 and 2.65 t 0.41
Abstracts
We have previously observed that in human placentas perfused in vitro, HCG, LH and CAMP have a stimulating action on aromization as well as on glycogenolysis. Prostaglandins FZ2, E, and chiefly E, induce also a significant increase in oestrogen production from testosterone. CAMP concentration in placental fragments taken during the experiments and assayed by a binding method was constant during blank experiments, but increases significantly 5 min after addition of HCG, LH and prostaglandins. The intensity and the duration of the stimulatory action of prostaglandins is more important than the action of gonadotropins, both on aromatization and on CAMP level. The glycogen phosphorylase enzyme system is also activated by HCG, LH. prostaglandins and CAMP. These findings confirm and extend our previous hypothesis of a mechanism of action of HCG on placental steroidogenesis mediated by CAMP. and suggest the possibility that prostaglandins may play a second messenger role in this action. Furthermore, incubations of full-term placental slices have shown efficient fixation of I,,, HCG, the specificity of which is under investigation.
13B. Prostaglandins in steroid biosynthesis 445. Effect of gonadotrophins on prostaglandin production by the rat ovary BAUMINGER,S. and LINDNER, H. R., Department of Biodynamics, The Weizmann Institute of Science, Rehovot. Israel The possibility of prostaglandin involvement in the process of follicular rupture was tested by determining prostaglandin levels. as well as prostaglandin synthetase activity in rat ovaries. Prostaglandin E2 levels were low (15-30 pg/mg tissue) in rat ovaries during the whole oestrous cycle, except on the evening of proestrus, after the peak of LH secretion. Prostaglandin EZ content at this period was increased 8-10 fold. Injection ofindomethacin, which was shown to prevent ovulation, lowered prostaglandin E, content of the ovaries. Injection of luteinizing hormone (10 pg/rat) on the morning of proestrus increased the level of PGE, in 4 h, but not at 2 h, to the same extent as seen in nontreated female rats at the evening of proestrus. Here again, indomethacin was an effective inhibitor of prostaglandin formation. FSH (100 pg/rat) wasequally effective in increasing prostaglandin E2 content. The activity of the enzyme system synthesizing prostaglandin was not significantly altered in the LH and FSH treated rats. Thus the possibility exists that the rise in prostaglandin content after the LH surge may be due to increased availability of the precursor arachidonic acid. perhaps resulting from stimulation of phospholipase.
446. Effect of prostaglandin F2. on the ovarian ascorbic acid and plasma progesterone levels of immature pseudopregnant rats SUNDARAM.K., The Population Council. The Rockefeller University, New York, 10021, U.S.A. The ovarian ascorbic acid depletion (OAAD) test has widely been used as a specific bioassay for LH and LH-like substances. LH is considered luteotropic while prostaglandin F,, (PG) is considered luteolytic. In this study the effect of PG on the OAAD test and plasma progesterone (P) levels (RIA) has been examined. Immature rats were prepared
for the OAAD test according to the method of Parlou. LH (NIH-LH-Sl8), 4.Opg i.v.. decreased the OAA to 56”,, and increased the P to 133”,, of control values. PC; (2OOpg SC) decreased the OAA to 78”,, and the P to 52”,,. Concomitant injection of LH overcame the effect of PG on the P level which increased to 124”,, but further depressed OAA to 541;. PG (IOO~~g/uterine horn) depressed the P to increased P to 21”:. and OAA to 56”:. LH. concomitantly, 110”” but further depressed OAA to 3c)“,,. The greater effectiveness of PG by the intrauterine route compared to the SCroute suggests a direct effect on the ovary. These data indicate that: (I) The OAAD test can be influenced by nongonadotropic substances and (7) that the changes in OAA levels do not always reflect the steroidogenic activity of the corpora lutea. (Supported by grant no. PO1 HD 05 71-UI from NICHHD). 447. Effects of prostaglandin PgF2a on progesterone and estrogen secretion by rabbit granulosa cells luteinized in tissue culture BATTA, S. K. and NICOSIA.S. V.. Dept. of ObstetricsGynaecology. University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19174, U.S.A. An in vitro corpus luteum system (Nicosia. S. V.. Fer/i/ Steril 23, 791. 1972) was used to study the influence of PgF2z on luteal steroidogenesis. Rabbit parietal granulosa cells and cumuli oophorii luteiniled during a 4 day culture period in X5”,, M199. 15”,, heat-inactivated serum. and antibiotics (C). following which they were fed for additIonal 4 days with medium C alone or enriched with PgF2r. IO0 (S) or 500 (L) pg/ml. No significant changes in the morpholog> ofluteinized granulosa cells were noted with PgF2;(. Oocq teh remained morphologically well preserved during the first 3 days of explantation. after which parthenogenetic cleuvugcs were seen (33”,,) both in C and PgF2r cultures. Radioimmunoassayable progesterone (pg!ml ; means i SD) decreased from the fourth (D4) to the eighth (D8) day. more significantly (p ~0.1) in PgFZx (D4: S-1620*960. L-1080 +780; D8: S-930+_400, L-490*330) than in C cultures (D4: 14OOi 1080. D8: 1200+970). In contrast, preliminar!, estrogen values indicated an increase (from 56 to 192 pg, ml) in PgFZti-S and insignificant changes in C and PgFZr-L cultures. Under such experimental conditions and doses, these results suggest that PgF2r may exert a direct influence on the steroidopoietic characteristics of luteinized granulosa cells without obviously affecting their morphology. 448. Hormonal changes occurring in cattle around normal oestrus and following administration of several luteolytic prostaglandins NANCARROW.C. D.. RADFORL).H. M., CO&NELL.P. J. and MATTNER, P. E.. C.S.I.R.O.. Division of Animal Physiology, Prospect, N.S.W.. Australia, 2148 Assessment of the effectiveness of synthetic and natural11 occurring luteolytic prostaglandins requires demonstration of both luteolysis, and the absence of abnormal changes associated with subsequent oestrus and ovulation. Prostaglandins were administered to 119 cows between days 6-16 of their oestrous cycle and blood collected at ?4h intervals. Plasma progesterone concentrations (ng,‘ml, . mean f SE.) at 0, 24 and 48 h in cows exhibiting oestrus within 5 davs (n = 113) were 743 + 0.21. I.27 + 0.05 and 0.06 + 0.03: while in cows exhibiting oestrus after 6 days (n = 6) they were 6.52 i 0.61. 2.38+ 0.62 and 2.65 t 0.41