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At least 19 recordsLinked to original sources

PubMed1976

Prolactin and delayed pseudopregnancy in the rat.

In (RXU)F1 hybrid rats delayed pseudopregnancy was induced in three different ways: 1) by removal of all recent corporl lutea on day 2 of pseudopregnancy, 2) by removal of the in situ ovaries from ovarian graft-bearing animals on day 0 of pseudopregnancy, 3) by administration of 1 mg of ergocornine hydrogenmaleinate (ECO) on day 1 of pseudopregnancy. These procedures ended pseudopregnancy and in 50-60% of the animals a delayed pseudopregnancy with a duration of 6-15 days was observed after the experimental cycle. After sterile copulation two daily prolactin peaks were observed. Removal of the ovaries in situ (from ovarian graft-bearing animals) or of recently formed corpora lutea (from non-grafted animals) caused the disappearance of the prolactin peak at 19.00 h, without affecting the occurrence of the 03.00 h peak. The administration of ECO caused the disappearance of both prolactin peaks. Until the day of estrus prior to delayed pseudopregnancy there were no differences in prolactin concentrations at 03.00 or 19.00 h between animals which became delayed pseudopregnant and those which remained cyclic. In the latter animals the 03.00 h surges decreased slowly in the luteectomized and the ovariectomized animals and were no longer present 7-9 days after copulation. In animals becoming delayed pseudopregnant both prolactin peaks were present from day 0 of delayed pseudopregnancy onwards. Progesterone cencentrations during delayed pseudopregnancy were relatively low when delayed pseudopregnancy had a duration of 6-9 days. When delayed pseudopregnancy lasted 10 days or more normal progesterone values were found.

Animals↗

PubMed1976

Serum follicle-stimulating hormone, luteinizing hormone and progesterone concentrations in pseudopregnant rats treated with medroxyprogesterone acetate.

Pseudopregnant rats were treated early in pseudopregnancy with 1 or 10 mg medroxyprogesterone acetate (MPA). Serum FSH, LH and progesterone concentrations were determined on days 2-20 of pseudopregnancy in treated and control rats. The mean duration of pseudopregnancy was 13-5 days in the control animals, but when animals were treated with 1 mg MPA a dioestrous period of 21-4 days was observed. A period with leucocytic vaginal smears of at least 2 months was observed after treatment with 10 mg MPA. Injection with MPA on day 3 of pseudopregnancy did not affect the serum FSH concentrations during the subsequent days. The progesterone pattern was alike in the three groups of animals, i.e. the duration of the activity of the corpora lutea was similar in all groups. However, 10 mg MPA slightly lowered progesterone concentrations on days 4-8 of pseudopregnancy. In the saline-treated rats, LH concentrations decreased from days 2-5, and remained low until they increased after day 11 of pseudopregnancy. This increase was delayed until day 20 in the animals treated with 1 mg MPA, and was not observed in the animals treated with 10 mg MPA. It is argued that the increase of LH concentration at the end of pseudopregnency is not instrumental in the decrease of peripheral progesterone concentration but rather that the decrease in the progesterone concentration leads to the increase in the LH concentration.

Animals↗

PubMed1979

Effects of PGE1 or PGE2 on luteal function in pseudopregnant rats.

Effects of PGE1 or PGE2 on luteal function were studied in 163 pseudopregnant rats. PGE1 (10, 100, or 300 micrograms) given intrauterine every 6 hr did not shorten pseudopregnancy (P greater than 0.05), however, the same doses of PGE2 given intrauterine every 6 hr advanced luteolysis (P less than 0.05). PGE1 (100 or 300 micrograms) given every 4 hr intramuscular maintained levels of progesterone in peripheral blood above controls (P less than 0.05) while 100 or 300 micrograms of PGE2 hastened the decline in progesterone (P less than 0.05). The antiluteolytic effect of PGE1 was not via an inhibition of PGF secretion (P greater than 0.05) by the uterus or by induction of ovulation in treated animals. Moreover, PGE1 (100, 200, or 500 micrograms) given intramuscular every 4 hr from day 4 of pseudopregnancy until the next proestrus delayed luteal regression around 3 days (P less than 0.05). PGE2 at doses of 100, 200, or 500 micrograms every 4 hr given intramuscular consistently shortened pseudopregnancy (P less than 0.05). Lower doses were without effect (P greater than 0.05). Based on the above data it is concluded that PGE2 is consistently luteolytic whereas PGE1 is not luteolytic in pseudopregnant rats and that PGE1 may be an antiluteolysin.

Animals↗

PubMed1979

Relationship of luteal blood flow and corpus luteum function in pseudopregnant rats.

An experiment was conducted to examine whether blood flow to corpora lutea may regulate luteal function as judged from plasma levels of progesterone (P) in mature pseudopregnant rats. 141Ce-labeled microspheres (14.1 +/- 0.8 micrometer diam) were used to measure cardiac output and organ and tissue blood flow in rats on days 6, 8, 10, and 12 of pseudopregnancy and in proestrus following luteal regression. The mean arterial blood pressure and cardiac output were similar among all groups of rats. Although a significant (P less than 0.05) decrease in plasma P was observed in rats on day 12 of pseudopregnancy, no change in luteal blood flow or distribution of ovarian blood flow to the corpora lutea was seen at this stage of pseudopregnancy when compared to day 8 or 10 of pseudopregnancy. However, a significant decrease (P less than 0.05) in luteal blood flow was seen in proestrous rats. Because a decrease in plasma progesterone preceded the decrease in luteal blood flow, it was concluded that physiological luteal regression may not be initiated by a reduction of blood flow to the corpus luteum.

Animals↗

PubMed1976

Prolactin: the initial luteotropic stimulus of pseudopregnancy in the rat.

The luteotropic stimuli necessary to transform the corpus luteum of the estrous cycle into a corpus luteum of psuedopregnancy on the morning of diestrus-2 (Day 2), as reflected by a dramatic divergence in progesterone secretion, were studied (Day 1 was taken as the first day of diestrus of pseudopregnancy). The requirement of prolactin (PRL) as a luteotropic stimulus was determined by inhibiting the diurnal and nocturnal PRL surges that occur immediately before and during the divergence in progesterone. Following cervical stimulation, 1 mg of 2-Br-alpha-ergocryptine (EC) was injected at 1100 and 2300 h on Day 1 (lights on 0600-1800 h), and the animals were decapitated at 2-4 h intervals from 1100 h on Day 1 to 1700 h on Day 2. In the control animals, the PRL surges on Day 1 and Day 2 were associated with an increase in progesterone secretion on Day 2. However, the regimen of EC treatment resulted in an inhibition of PRL surges, prolactin remaining at baseline values from 1100 h on Day 1 to 1700 h on Day 2. The inhibition of PRL secretion was associated with a fall in progesterone concentration to reach baseline values by 1700h on Day 2. Furthermore, a group of animals similarly treated with EC returned to vaginal estrus 2 days later. LH concentrations did not differ in control and EC-treated animals. The effect of EC on corpus luteum function could be completely reversed by the simultaneous administration of PRL. In addition, if PRL was administered at 1100 h and 2300 h on diestrus-1 of the estrous cycle, in an attempt to mimic the surges os pseudopregnancy, regression of the corpora lutea did not occur. Progesterone levels increased to reach values comparable to those observed in pseudopregnancy on diestrus-2. The role of LH was studied by administering a dose of LH antiserum at 110 and 2300 h on Day 1 of pseudopregnancy. This treatment failed to inhibit the increase in progesterone observed on Day 2. These results demonstrate that the surges of plasma PRL initiated by cervical stimulation are responsible for transforming a corpus luteum of the estrous cycle into a corpus luteum of pseudopregnancy, as reflected by an increase in progesterone secretion of Day 2. LH seems to have a minor role in maintaining corpus luteum function beyond that observed during the estrous cycle.

Animals↗

PubMed1978

CL regression in the pseudopregnant rabbit and the effects of treatment with prostaglandin F-2alpha and arachidonic acid.

During pseudopregnancy in the rabbit, plasma progesterone levels in the posterior vena cava fell rapidly from maximal concentrations of 9.8 +/- 0.7 (s.e.m.) ng/ml on Day 13 of pseudopregnancy to 2.0 +/- 0.6 ng/ml on Day 15. There was no significant increase in PGF levels at this time, although administration of indomethacin to a similar group of does delayed functional regression for over 7 days. Subcutaneous injection of 1 mg PGF-2alpha or 35 mg arachidonic acid on Day 9 of pseudopregnancy resulted in loss of luteal function as plasma progesterone levels fell significantly from about 6 to less than 1 ng/ml within 24 h. These findings indicate that the uterine factor responsible for luteolysis in the pseudopregnant rabbit may not be released in the form of PGF-2alpha.

Animals↗

PubMed1979

Measurement of thymus weight, lumbar node weight and progesterone levels in syngeneically pregnant, allogeneically pregnant, and pseudopregnant mice.

Female CBA mice were mated to fertile CBA males, to vasectomized CBA males, to fertile C57BL males or to vasectomized C57BL males. After allogeneic or syngeneic mating the extent of thymic involution on the 10th day of pregnancy and pseudopregnancy was similar. Lumbar lymph node weight was not affected by pseudopregnancy but increased similarly in allogeneic and syngeneic pregnancies. Serum progesterone levels on the 10th day of pseudopregnancy were similar to those of non-pregnant females, and significantly lower than those of pregnant females. On the 4th to 7th days progesterone levels in pseudopregnant animals were equal to those in pregnant animals. Progesterone levels and thymic involution were similar in syngeneically and allogeneically pregnant females. Progesterone levels were negatively correlated with thymus weight but reached significance only when the mating was allogeneic. It is suggested that there is an interaction between progesterone concentrations and the degree of thymic involution during pregnancy.

Animals↗

PubMed1979

Prostaglandin-induced luteolysis in pregnant and pseudopregnant rabbits and the resultant effects on the myometrial activity.

The effect of prostaglandin (PG)-induced luteolysis on the myometrial activity in 20--21-day-pregnant and 11--12-day-pseudopregnant rabbits was studied by intrauterine pressure (IUP) recording during PG infusions. The same dose of PG (10 micrograms/h during 8h) was also given to 7 non-pregnant (untreated) does that were used as controls. Peripheral plasma concentration of progesterone and oestradiol-17 beta were measured at 2-h intervals during the infusion. Plasma progesterone level decreased significantly within 2 h or the start of infusion in pregnant and pseudopregnant does and continued to decrease; at the end of 8 h, the concentrations were 31 and 41%, respectively, of the pre-infusion levels. The amplitude of uterine contractions increased significantly after 4 h in pseudopregnant does, increased slightly but insignificantly in the pregnant does and showed no significant change in the non-pregnant does during PG infusion. The amplitudes developed in the pregnant and pseudopregnant does were significantly different. The direct effect of progesterone (1--3 micrograms/h during 4 h) was also studied in 7 non-pregnant rabbits. After 2 h the amplitude of contractions had decreased markedly and the pattern of activity had become irregular. The results support the concept of a myometrial inhibitory factor other than progesterone in rabbit pregnancy and suggest that this factor(s) originates in conceptus.

Animals↗

PubMed1976

Conservative treatment of endometriosis: the effects of limited surgery and hormonal pseudopregnancy.

This study compares the effects of limited surgery or hormonal pseudopregnancy, or a combination of these two, upon fertility and the need for subsequent surgery with respect to the extent of the disease at the time of initial diagnosis in patients with endometriosis externa. Of the 61 patients who desired to enhance or preserve reproductive capacity, 20 patients became pregnant, for a pregnancy rate of 33%. The pregnancy rate in all categories, that is, those patients treated with pseudopregnancy, conservative surgery, and combined pseudopregnancy and surgery, was found to be in direct relationship to the initial extent of disease. In such patients, conservative surgery alone seemed to give the best results in the achievement of pregnancy. There seemed to be little difference between pseudopregnancy alone and conservative surgery in regard to the need for subsequent surgery after initial therapy, although there seemed to be a significantly greater chance for the need for subsequent surgery in patients receiving a combination of the two forms of therapy. The need for subsequent surgery after initial therapy in 80 patients increased in direct relationship to the initial extent of disease present, despite the form of therapy used. Fifty-nine other patients with endometriosis, who did not desire to preserve fertility and presented for relief of other symptoms, underwent initial "radical" therapy. Forty-six patients underwent complete operation, including removal of uterus, tubes and ovaries, and none required subsequent reoperation. Of the 13 remaining patients, who underwent incomplete surgical removal, leaving one or both ovaries in situ, 11 required subsequent reoperation for recurrent pelvic endometriosis.

Adolescent↗

PubMed1979

Prostaglandins F in uterine and ovarian compartments and in plasma from the uterine vein, ovarian artery and vein, and abdominal aorta of pseudopregnant rats with and without deciduomata.

Prostaglandins F were measured in uterine and ovarian compartments and in uterine venous, ovarian arterial and venous and abdominal aorta plasma and the uptake of 3H-PGF2 alpha by ovarian compartments of 240 pseudopregnant rats with or without bilateral deciduomata in five experiments. Concentrations of PGF in deciduomal tissue, uterine venous plasma, ovarian arterial and venous plasma, corpora lutea, and remainder of the ovary and 3H-PGF2 alpha in the ovary were consistently as high or higher in pseudopregnant rats with deciduomata as in the endometrium, ovarian compartments, or samples of plasma from the same blood vessels of pseudopregnant rats without deciduomata. Levels of PGF were consistently 3 to 7 fold higher in uterine venous than in plasma from the abdominal aorta. It is concluded that extended luteal maintenance by deciduomal tissue is by some mechanism other than an inhibition of PGF synthesis by the uterus, transfer of PGF locally to the ovary, or uptake of PGF by the ovarian compartments.

Animals↗

PubMed1979

Serum prolactin concentrations during hormonally induced pseudopregnancy in the rat.

Treatment of 5-day cyclic rats with 10 or 100 microgram estradiol benzoate on the day of estrus induced a luteal phase in all animals studied. On the other hand, an injection with 1 microgram estradiol benzoate given on the same day failed to induce pseudopregnancy. When 10 mg progesterone were injected on the day of estrus, about 50% of the rats became pseudopregnant, whereas most of the remaining rats had a 6-day cycle. The injection of 10 or 100 microgram estradiol benzoate or 10 mg progesterone induced a period of increased PRL secretion which lasted for 2--4 days, followed by twice daily surges of PRL at the end of the dark and light periods, respectively. It is argued that pseudopregnancy induction by estradiol benzoate or progesterone is primarily a result of the induction of a period of increased PRL secretion. In this way, progesterone secretion by the recently formed corpora lutea is induced, and the elevated levels of progesterone in turn generate diurnal surges of PRL.

Animals↗

PubMed1976

Adenylyl cyclase activities in ovarian tissues. IV. Gonadotrophin-induced desensitization of the luteal adenylyl cyclase throughout pregnancy and pseudopregnancy in the rabbit and the rat.

We measured the adenylyl cyclase (AC) activity in dissected CL and the responsiveness of the AC system to LH, FSH, and prostaglandin (PG)E1 at different times following the administration of high doses of hCG or hLH to pseudopregnant and pregnant rats and rabbits. In rabbits, ovulatory doses of hCG promoted desensitization of the AC system in both CL of pregnancy and CL of pseudopregnancy (PSP), but at varying rates. At least a 50% decline in the LH-stimulated AC system was demonstrable 2 h after the hCG injection in CL obtained during PSP and the first 18 days of pregnancy. However, after day 21, AC activity was unaltered at 2 or 24 h after hCG injection, necessitating as much as 72 h for the AC system to become desensitized to LH. It seems that CL in the last third of pregnancy are afforded partial protection from the desensitizing effects of hCG. This protective effect was found not to be conferred upon follicles contained in ovaries after day 21 of pregnancy or upon newly, hCG-induced 3-day-old CL in 24-day pregnant rabbit ovaries. hCG-induced desensitization of CL adenylyl cyclase in rabbits was prevented neither by cauterization of tertiary follicles not by the continued administration of estradiol-17beta (1.5 mug SC twice daily), suggesting that this effect of hCG is due to a direct interaction with the CL, and not due to interruption of the follicular estrogen supply. In rats, the injection of an ovulatory dose of hCG (50 IU SC into prepubertal rats; 50 IU ip plus 50 IU SC into mature rats) also induced desensitization of the AC system in ovaries of superovulated prepubertal rats and in CL of pseudopregnant and pregnant rats. Desensitization of the AC system was not detectable at 2 h, was 30% of total by 6 h, and was complete at 24 h after hCG injection. Both regression of the CL and desensitization of the AC system in CL are induced only by doses of hCG which are ovulatory and not subovulatory. Desensitization of AC appears to precede functional luteolysis, at least in the pseudopreganant rabbit. Thus, the apparent close association between hCG-induced luteolysis and the desensitization of the adenylyl cyclase system in CL would suggest that desensitization may be a marker for luteal regression.

Adenylyl Cyclases↗

PubMed1975

Effect of prostaglandin E2 on oviductal adenosine 3':5'-monophosphate levels during estrus and pseudopregnancy.

The basal levels of adenosine 3':5'-monophosphate (cyclic AMP) in the oviductal isthmus were lower during pseudopregnancy than during estrus. No differences were observed in the ampulla. Prostaglandin E2(PGE2) significantly increased cyclic AMP levels in the isthmus during pseudopregnancy but not during estrus. In contrast, in the ampulla, PGE2 did not alter cyclic AMP levels in either hormonal condition. Theophylline increased cyclic AMP levels in the isthmus and in the ampulla during pseudopregnancy. These results show that PGE2 causes a specific increase in cyclic AMP levels in the isthmus after ovulation.

Adenosine Monophosphate↗

PubMed1978

Ovarian ornithine decarboxylase regulation in the immature, the pubescent, and the pseudopregnant rat.

Ovarian ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) regulation was investigated in immature, pubescent, and pseudopregnant rats. After initial induction of the enzyme by injection of lutropin in the immature rat, continued daily injections resulted in a graded decrease in the activity of the enzyme. In the 32-day-old rat, the induction and subsequent decline in enzymic activity after a single injection of lutropin could only be partially reversed by injections of the hormone at 4-hr intervals. This decrease could not be attributed to a decrease in ovarian in vivo uptake of the hormone. In the pseudopregnant rat, ovarian ornithine decarboxylase is highly refractory to induction by either a single injection or repeated injections of lutropin. This refractoriness occurs despite a 2- to 3-fold increase in ovarian in vivo uptake of the hormone compared to that in the 32-day-old rat. It is suggested that the refractoriness observed with all three tissues is a function of cell differentiation.

Animals↗

PubMed1977

Termination of pseudopregnancy following hypothalamic implantation of prolactin.

Pseudopregnancy (PP) in the rat is characterized by maintenance of the corpora lutea and twice daily surges of prolactin at 1500-2100 h and 0100-0900 h. Four days after PP was induced by cervical stimulation with a glass rod, rats were cannulated via the right carotid artery and one day later received an implant of ovine prolactin (200-250 mg) or albumin (controls) into the median eminence of the hypothalamus. Forty-five of 54 rats implanted with prolactin showed a termination of PP within 4 days. Ova were recovered from 19 of these rats whereas all of the controls remained pseudopregnant and did not ovulate. Ovarian and uterine weights were increased in rats implanted with prolactin. Plasma prolactin levels in the rats implanted with prolactin were lower each day (45-89%) at 0100, 0300 and 1800 h compared to controls. Plasma LH levels rose gradually after prolactin implantation, and in those rats in which ovulation occurred, a preovulatory LH rise was detected at 1800 h on the previous day. It is concluded that daily surges of prolactin play an essential role in maintaining PP in the rat, and that implantation of prolactin into the median eminence results in inhibition of prolactin. The stimulation of LH secretion, which led to ovulation, may be the result of a direct neural action of prolactin on the LH release mechanism or may simply result from the termination of PP.

Animals↗

PubMed1975

Premature regression of corpora lutea in pseudopregnant rabbits following the removal of polydimethylsiloxane capsules containing 17 beta-estradiol.

17-beta-Estradiol, which is luteotropic in rabbits, was administered during pseudopregnancy via polydimethylsiloxane (Silastic) implants to determine the effects on serum progesterone concentrations. Implants which released estradiol at a rate of approximately 2 mug/day were place beneath the skin the day after sterile mating and ovulation (day 0). Blood (3 ml) was obtained from the marginal ear vein on days 3, 6, 9, 10, 11 and 12. Serum estradiol levels, determined by radioimmunoassay, were 2- to 3-fold higher in estradiol-treated rabbits (11.7 plus or minus 1.2 pg/ml) than in untreated pseudopregnant controls (5.9 plus or minus 1.4 pg/ml). Weights of corpora lutea in treated and control rabbits were not different at the conclusion of the experiment on day 12. Serum progesterone concentrations, also determined by radioimmunoassay, were not significantly different between treated and control animals. However, when estradiol implants were removed from other rabbits on day 10, a rapid decline in serum progesterone occurred, from 14.0 plus or minus 2.4 to 2.6 plus or minus 0.8 ng/ml 24 h later. By comparison, serum progesterone concentrations in rabbits with estradiol implants left in place and in untreated rabbits on day 12 were similar (similar to 12 ng/ml). The premature decline in serum progesterone was accompanied by a decrease in the wet weight of corpora lutea. Other experiments revealed: 1) a precipitous fall in serum estradiol to basal values within 2 h after estradiol implants were removed, preceding the decline in serum progesterone by approximately 6 to 10 h; 2) reduced levels of estradiol in ovarian venous blood, but elevated levels of estradiol in peripheral arterial blood of rabbits with estradiol impants. The inability to elevated estradiol to increase serum progesterone or weights of corpora litea suggests that the luteotropic effect is maximal when estradiol is present at physiological concentrations. Following the continuous administration of estradiol, ovarian secretion of estradiol appears diminished and the corpora lutea become dependent upon the exogenous estradiol for luteotropic support. Although the ovaries continue to release measureable quantities of estradiol, this is inmeasurable quantities of estradiol, this is insufficient to prevent regression of corpora lutea when exogenous estradiol is rapidly withdrawn from the circulation.

Animals↗

PubMed1978

Effects of medial hypothalamic deafferentation on prolactin secretion in pseudopregnant rats.

Frontal hypothalamic deafferentation (FHD), which disconnects the anterior hypothalamus from the preoptic area, stops the twice daily surges of prolactin secretion of pregnancy or pseudopregnancy in the rat, and causes rapid luteolysis. Medial hypothalamic deafferentation (MHD), which separates the anterior from the posterior half of the hypothalamus, does not interrupt pregnancy and causes a significant increase in the size of the corpora lutea. To see whether MHD induces an increase in the basal level of prolactin secretion and/or a change in the pattern of prolactin surges, pseudopregnant rats were subjected to MHD or a sham operation on day 3 (day 1 = day of oestrus) and their bloods assayed for prolactin on either day 5 or days 7--8. MHD caused a specific disappearance of the day-time prolactin surge and a diminution in the height of the night-time surge, but no change from the controls in the basal prolactin level. In spite of what thus appears to be a lesser secretion of prolactin than in the controls, the corpora lutea of the MHD rats were larger, and progesterone was secreted at a higher rate and for a longer time, than in the controls. The relation of these findings to the existence of a "surge centre" in the hypothalamus was discussed.

Afferent Pathways↗

PubMed1979

Lymphoid response to pregnancy and pseudopregnancy in the rat.

Differences in weight, while cell density and differential white cell count of the thymus, spleen, iliac and popliteal lymph nodes of virgin, 10 days outbred pregnant, 10 days inbred pregnant, 10 days pseudopregnant, and 40 days outbred post-coitum rat were examined. Compared with virgin animals, significant weight gain occurred only in the thymus, spleen and iliac lymph nodes of the outbred group. Significant weight loss from the thymus and iliac nodes, and significant reductions in white cell density of the spleen and popliteal nodes occurred in delivered animals when compared with the virgin group. During pseudopregnancy significant weight loss occurred from the thymus, spleen and popliteal lymph nodes compared with the inbred group, and from the iliac lymph nodes compared with the virgin group. No significant differences were observed between the proportions of proliferating cells in the lymphocyte populations of the thymus, spleen, iliac and popliteal lymph nodes of the virgin group. In the outbred group the proliferating populations of all four tissues rose significantly above virgin levels, while in the inbred group only the iliac lymph nodes showed any significant rise above the virgin value. These findings are discussed in relation to the maternal immunological response to pregnancy.

Animals↗