Inactivation of prostaglandin E2 by rat isolated lung during the oestrous cycle

1983 ◽  
Vol 98 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Y. S. Bakhle ◽  
J. T. Zakrzewski
Keyword(s):  
Enzyme Activity ◽  
Pulmonary Circulation ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Pulmonary Vasculature ◽  
Prostaglandin E ◽  
Isolated Lung ◽  
Tissue Homogenates ◽  
Isolated Lungs ◽  
Isolated Rat Lung

The metabolism of prostaglandin E2 (PGE2) in lungs from female rats was measured during the stages of the oestrous cycle. In isolated lungs perfused through the pulmonary circulation, only 7–20% of PGE2 escaped metabolism, as measured by bioassay and radioimmunoassay. Within these limits, survival was highest at pro-oestrus compared with metoestrus and dioestrus. Uptake of PGE2 from the pulmonary vasculature, assessed by measuring the efflux of radioactivity derived from [14C]PGE2 injected into the pulmonary circulation of the isolated lung, did not show cycle-related variations. Assay of [14C]PGE2 metabolism by tissue homogenates prepared from lungs taken at different stages of the oestrous cycle showed a significant decrease in enzyme activity at pro-oestrus compared with dioestrus. It is concluded that PGE2 metabolism in isolated rat lung is affected by the oestrous cycle and that the increased PGE2 survival at pro-oestrus may be more readily explained by changes in enzyme activity than by changes in uptake of substrate.

Cyclic and diurnal alterations in the response of luteinizing hormone and prolactin to prostaglandin E2 during the rat oestrous cycle

1984 ◽  
Vol 106 (1) ◽  
pp. 30-37 ◽  
Author(s):  
Lise Wogensen ◽  
Jørgen Warberg
Keyword(s):  
Luteinizing Hormone ◽  
Prostaglandin E2 ◽  
Lateral Ventricle ◽  
Mature Female ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Male Rats ◽  
Prostaglandin E ◽  
The Brain ◽  
Time Of Administration

Abstract. Two μg of prostaglandin E2 (PGE2) was infused into a lateral ventricle of the brain of female rats at 09.00 or 13.00 h on the different days of the oestrous cycle and the effect on luteinizing hormone (LH) and prolactin (Prl) release was determined. At 09.00 h PGE2 caused a pronounced release of LH in pro-oestrous, oestrous and metoestrous rats whereas the LH response in dioestrous rats was moderate. The secretion of Prl was only stimulated in rats from the pro-oestrous phase. When infused at 13.00 h PGE2 had a marked stimulatory effect on the release of LH in all groups of rats. The response was almost the same in oestrous, metoestrous and dioestrous rats but pro-oestrous rats a 2-fold higher LH response was observed. On each day of the oestrous cycle it was found that the LH-releasing activity of PGE2 was greater at 13.00 h than at 09.00 h. Thus, the overall greatest responsiveness of LH to PGE2 was noted at 13.00 h on pro-oestrus i.e. at a time which was prior to the onset of the spontaneous LH surge. At 13.00 h – as at 09.00 h – PGE2 was only capable of stimulating Prl release in pro-oestrous rats. Resembling the LH response it was found that PGE2-induced Prl release was greater at 13.00 h than at 09.00 h. In adult male rats the stimulatory effect of PGE2 on LH and Prl release was independent of the time of administration. It is concluded that the neuroendocrine elements of the hypothalamo-pituitary unit in mature female rats exhibit cyclic as well as diurnal alterations in the responsiveness to PGE2.

Plasma and platelets potentiate a hypoxic vascular response of the isolated lung

1981 ◽  
Vol 51 (4) ◽  
pp. 875-880 ◽  
Author(s):  
S. Kivity ◽  
J. F. Souhrada
Keyword(s):  
Pulmonary Circulation ◽  
Acute Hypoxia ◽  
Pulmonary Vasculature ◽  
Physiological Salt Solution ◽  
Hypoxic Response ◽  
Rat Lungs ◽  
Isolated Lung ◽  
Alveolar Hypoxia ◽  
Isolated Rat

To determine whether plasma and /or platelets play a role in the hypoxic response of pulmonary circulation, we perfused isolated rat lungs with different concentrations of plasma and varying numbers of platelets. As the lungs were perfused with a constant flow (8–13 ml/min), a change in the mean pulmonary artery perfusion pressure (PApP) during acute alveolar hypoxia was a measure of increased tone of the pulmonary circulation. It was found that the presence of plasma in the perfusate (both 20% and 100%) significantly (P less than 0.05) potentiated the PApP response during repeated acute alveolar hypoxia, compared with the response to artificial perfusate without plasma. An isolated rat lung perfused with 6.5% dextran or 3% albumin (both in a physiological salt solution) showed only minimal pressure response during acute alveolar hypoxia. In the second part of the experiment, isolated lungs were perfused with a fresh 100% plasma containing different numbers of platelets. A dose-response-like relationship was observed between the number of platelets in the perfusate and the response of the pulmonary vasculature to acute hypoxia. The highest hypoxic response of the pulmonary vessels, as indicated by the increase in PApP, was shown when the perfusate contained a nearly normal in vivo number of platelets. It can be concluded that both plasma and platelets are important factors that can significantly alter the hypoxic response of the pulmonary vasculature in isolated rat lungs.

THE ACTIVITY OF AN LH-RH-DEGRADING ENZYME IN THE ANTERIOR PITUITARY DURING THE RAT OESTRUS CYCLE AND ITS ALTERATION BY INJECTIONS OF SEX HORMONES

1978 ◽  
Vol 87 (3) ◽  
pp. 476-484 ◽  
Author(s):  
Herbert Kuhl ◽  
Christian Rosniatowski ◽  
Hans-Dieter Taubert
Keyword(s):  
Enzyme Activity ◽  
Enzyme System ◽  
Maximal Activity ◽  
Female Rats ◽  
Prostaglandin E ◽  
Degrading Enzyme ◽  
Oestrus Cycle ◽  
System L ◽  
Lh Release ◽  
Lh Rh

ABSTRACT The basal activity of an LH-RH-degrading enzyme system, L-cystine arylamidase, was determined in the pituitary gland of female rats at 4 h intervals throughout the 4-day oestrus cycle. The activity of the enzyme was found to be fluctuating during the four stages of the cycle in a circadian rhythm with the highest values occurring at night and the lowest values at noon. The maximal activity for the whole cycle was measured at 04.00 h on the day of metoestrus, and the minimal activity between 12.00 h and 16.00 h on the day of pro-oestrus. The iv injection of various doses of oestradiol caused only a slight change in enzyme activity of the pituitary during oestrus, but considerable increases were observed during the other three stages. The stimulation of enzyme activity by progesterone was much more pronounced during dioestrus and pro-oestrus as compared with metoestrus and oestrus. Similarly the reaction to the injection with LH and prostaglandin E2, repectively, were not very pronounced during oestrus and metoestrus, whereas the enzyme activity rose by +50% and +100%, respectively, during dioestrus and pro-oestrus. The LH-RH-degrading enzyme system in the pituitary seems to be involved in the control of the tonic LH release, and in the maintenance and regulation of the sensitivity of the gonadotrophs to alterations in LH-RH release from the median eminence.

CHANGES IN HYPOTHALAMIC PEPTIDASE ACTIVITY DURING THE OESTROUS CYCLE IN THE ADULT FEMALE RAT

1973 ◽  
Vol 74 (1) ◽  
pp. 41-48 ◽  
Author(s):  
E. C. Griffiths ◽  
K. C. Hooper
Keyword(s):  
Enzyme Activity ◽  
Luteinizing Hormone ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Male Rats ◽  
Supernatant Fraction ◽  
Normal Male ◽  
Normal Female ◽  
Peptidase Activity ◽  
Female Rat

ABSTRACT The activity of peptidases in the rat hypothalamus which are capable of inactivating oxytocin has previously been found to vary with stimuli known to influence gonadotrophin release and may be related to both luteinizing hormone (LH) and luteinizing hormone releasing factor (LH-RF) release (Griffith & Hooper 1972a,b). In the present study, enzyme activity was determined in normal female rats during the morning and afternoon of each stage of the oestrous cycle, in normal rats, and in female rats injected neonatally with testosterone. The activity of the supernatant fraction was found to be not significantly different during the morning of each stage, but was greatly decreased on the afternoon of pro-oestrus; particulate activity did not vary during the oestrous cycle. Supernatant and particulate activities were found to be the same in normal male rats and testosterone-treated females, as previously shown. Both fractions' activities were significantly less than those found in the oestrous cycle, other than on the afternoon of pro-oestrus. These results indicate changes in hypothalamic peptidase activity during the oestrous cycle which may be inversely related to LH and LH-RF release; they also confirm the masculinizing effect of neonatal testosterone on the hypothalamus.

NEW DATA CONCERNING THE ROLE PLAYED BY PROGESTERONE IN THE CONTROL OF FOLLICULAR GROWTH IN THE RAT

1974 ◽  
Vol 75 (3) ◽  
pp. 569-578 ◽  
Author(s):  
G. Buffler ◽  
S. Roser
Keyword(s):  
Wistar Rats ◽  
Venous Blood ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Cycle Duration ◽  
Follicular Growth ◽  
The Third ◽  
Female Wistar Rats

ABSTRACT The mechanisms involved in the prolongation of the oestrous cycle following LH administration were studied in 4-day cyclic female Wistar rats. In females injected with LH on the morning of dioestrus I there was an increase in ovarian venous blood progesterone as compared with non-injected animals. In both LH-treated females, and those injected with progesterone on the morning of dioestrus I, a slowing up in follicular growth was observed from the afternoon of dioestrus I. The size of follicles greater than 400 urn present in LH or progesterone injected animals on the third day of cycle was similar to the size reached by the same range of follicles in non-injected animals on the second day of the cycle. Hence, the increase in endogenous ovarian progesterone elicited by LH was considered as the cause of the slowing up of follicular growth and therefore of the lengthening of the oestrous cycle duration in female rats injected with LH at the beginning of 4-day cycle.

Changes in the characteristics of pulsatile luteinizing hormone secretion during the oestrous cycle and after ovariectomy and oestrogen treatment in female rats

1982 ◽  
Vol 94 (2) ◽  
pp. 177-182 ◽  
Author(s):  
Takashi Higuchi ◽  
Masazumi Kawakami
Keyword(s):  
Hormone Secretion ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Secretion ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Lh Release

Changes in the characteristics of LH secretory pulses in female rats were determined in different hormonal conditions; during the oestrous cycle and after ovariectomy and oestrogen treatment. The frequency and amplitude of the LH pulses were stable during the oestrous cycle except at oestrus when a pattern could not be discerned because of low LH concentrations. These were significantly lower than those measured during other stages of the cycle. Mean LH concentrations and LH pulse amplitudes increased with time up to 30 days after ovariectomy. The frequency of the LH pulse was unchanged 4 days after ovariectomy when mean LH levels had already increased. The frequency increased 10 days after ovariectomy and then remained stable in spite of a further increase in mean serum LH concentrations. Oestradiol-17β injected into ovariectomized rats caused a decrease in LH pulse amplitude but no change in pulse frequency. One day after treatment with oestradiol benzoate no LH pulse was detectable, probably because the amplitude was too small. A generator of pulsatile LH release is postulated and an oestrogen effect on its function is discussed.

Comparison of the hemodynamic effects of nitric oxide and endothelium-dependent vasodilators in intact lungs

1990 ◽  
Vol 68 (2) ◽  
pp. 735-747 ◽  
Author(s):  
S. L. Archer ◽  
K. Rist ◽  
D. P. Nelson ◽  
E. G. DeMaster ◽  
N. Cowan ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Methylene Blue ◽  
Pulmonary Hypertension ◽  
Feedback Inhibition ◽  
Pressor Response ◽  
Pulmonary Vasculature ◽  
Hemodynamic Effects ◽  
Isolated Lung

The effects of endothelium-dependent vasodilation on pulmonary vascular hemodynamics were evaluated in a variety of in vivo and in vitro models to determine 1) the comparability of the hemodynamic effects of acetylcholine (ACh), bradykinin (BK), nitric oxide (NO), and 8-bromo-guanosine 3′,5′-cyclic monophosphate (cGMP), 2) whether methylene blue is a useful inhibitor of endothelium-dependent relaxing factor (EDRF) activity in vivo, and 3) the effect of monocrotaline-induced pulmonary hypertension on the responsiveness of the pulmonary vasculature to ACh. In isolated rat lungs, which were preconstricted with hypoxia, ACh, BK, NO, and 8-bromo-cGMP caused pulmonary vasodilation, which was not inhibited by maximum tolerable doses of methylene blue. Methylene blue did not inhibit EDRF activity in any model, despite causing increased pulmonary vascular tone and responsiveness to various constrictor agents. There were significant differences in the hemodynamic characteristics of ACh, BK, and NO. In the isolated lung, BK and NO caused transient decreases of hypoxic vasoconstriction, whereas ACh caused more prolonged vasodilation. Pretreatment of these lungs with NO did not significantly inhibit ACh-induced vasodilation but caused BK to produce vasoconstriction. Tachyphylaxis, which was agonist specific, developed with repeated administration of ACh or BK but not NO. Tachyphylaxis probably resulted from inhibition of the endothelium-dependent vasodilation pathway proximal to NO synthesis, because it could be overcome by exogenous NO. Pretreatment with 8-bromo-cGMP decreased hypoxic pulmonary vasoconstriction and, even when the hypoxic pressor response had largely recovered, subsequent doses of ACh and NO failed to cause vasodilation, although BK produced vasoconstriction. These findings are compatible with the existence of feedback inhibition of the endothelium-dependent relaxation by elevation of cGMP levels. Responsiveness to ACh was retained in lungs with severe monocrotaline-induced pulmonary hypertension. Many of these findings would not have been predicted based on in vitro studies and illustrate the importance for expanding studies of EDRF to in vivo and ex vivo models.

scholarly journals Hypoxia recruits intrapulmonary arteriovenous pathways in intact rats but not isolated rat lungs

2012 ◽  
Vol 112 (11) ◽  
pp. 1915-1920 ◽  
Author(s):  
Melissa L. Bates ◽  
Brendan R. Fulmer ◽  
Emily T. Farrell ◽  
Alyssa Drezdon ◽  
David F. Pegelow ◽  
...  
Keyword(s):  
Intact Animal ◽  
Large Diameter ◽  
Rat Lung ◽  
Isolated Lung ◽  
Alveolar Hypoxia ◽  
Spontaneously Breathing ◽  
Isolated Rat Lung ◽  
Mixed Venous ◽  
Isolated Rat ◽  
Intact Rats

Intrapulmonary arteriovenous anastomoses (IPAVS) directly connect the arterial and venous circulations in the lung, bypassing the capillary network. Here, we used solid, latex microspheres and isolated rat lung and intact, spontaneously breathing rat models to test the hypothesis that IPAVS are recruited by alveolar hypoxia. We found that hypoxia recruits IPAVS in the intact rat, but not the isolated lung. IPAVS are at least 70 μm in the rat and, interestingly, appear to be recruited when the mixed venous Po2 falls below 22 mmHg. These data provide evidence that large-diameter, direct arteriovenous connections exist in the lung and are recruitable by hypoxia in the intact animal.

PRODUCTION OF PROSTAGLANDINS BY THE GUINEA-PIG UTERUS

1972 ◽  
Vol 54 (1) ◽  
pp. 147-159 ◽  
Author(s):  
N. L. POYSER
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Oestrous Cycle ◽  
Prostaglandin E ◽  
Prostaglandin F

SUMMARY The production of prostaglandins by the uterus and the resting levels of prostaglandins in the uterus on selected days of the oestrous cycle were determined in guinea-pigs. Prostaglandin F2α was detectable in the guinea-pig uterus in small amounts on days 13, 14 and 15 of the cycle. Prostaglandin E2 was present in even smaller amounts on days 14 and 15. The homogenized guinea-pig uterus had the ability to biosynthesize prostaglandins, from endogenous precursors, during incubation on every day of the cycle studied. Four to six times more prostaglandin F2α than E2 was produced on any one day with the amounts of prostaglandins formed increasing towards the end of the oestrous cycle. Indomethacin inhibited the biosynthesis of prostaglandins by the guinea-pig uterus. The implications of these findings are discussed.

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