Speculations on the Probable Role of Relaxin in Cervical Dilation and Parturition in Rats

Steinetz, Bernard G.; O’Byrne, E. M.

doi:10.1055/s-2007-1022594

Cited by 8 publications

(6 citation statements)

References 28 publications

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“…The results of this study are consistent with earlier findings that relaxin is required for rapid and safe delivery in the rat [26,[33][34][35][36][37]. Neither induction of early delivery nor abortion occurred after ovariectomy.…”

Section: Discussionsupporting

confidence: 94%

Role of Relaxin and Estrogen in the Control of Eosinophilic Invasion and Collagen Remodeling in Rat Cervical Tissue at Term1

Luque

Toro

Ramos

et al. 1998

Biology of Reproduction

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Ripening and dilation of the rat cervix at term involves a widespread reduction in the density and organization of collagen fibers following a polymorphonuclear eosinophilic invasion. These are hormonally regulated events; however, the correlation between hormonal milieu and these morphological changes is not well understood. To investigate the role of preparturient relaxin and estradiol-17ss (E2) in cervical collagen remodeling and eosinophilic infiltration, pregnant rats were either sham-ovariectomized (group C) or ovariectomized in the morning of Day 22. Ovariectomized rats were treated with E2 (group OE), relaxin (group OR), E2 plus relaxin (group OER), or hormone vehicles (group O). There were 4 or 5 animals per group. Cervices were taken from animals killed approximately 1 h before expected parturition. Five-micrometer serial sections of paraffin-embedded cervices were stained with either Sirius Red in alkaline solution to measure eosinophil infiltration or in Picrosirius to measure collagen birefringence. Ovariectomized rats treated with E2 (group OE or OER) showed high levels of eosinophilic infiltration that did not differ from those in group C intact controls. However, the values of eosinophilic infiltration in ovariectomized rats treated with relaxin or hormone vehicles (groups OR and O) were low and far below (p < 0.01) those of groups OE and C. In ovariectomized rats treated with E2 alone (group OE), the widespread reduction in collagen organization that occurred in group C controls was not observed. It was only in ovariectomized rats treated with relaxin or E2 + relaxin (groups OR and OER) that the values of birefringence were low, and they were as low as in control group C. In conclusion, this study indicates that eosinophilic infiltration and collagen remodeling in the rat cervix at term are under the control of different hormones: E2 stimulates eosinophilic invasion, and relaxin promotes a widespread reorganization of collagen fibers.

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Section: Discussionsupporting

confidence: 94%

Role of Relaxin and Estrogen in the Control of Eosinophilic Invasion and Collagen Remodeling in Rat Cervical Tissue at Term1

Luque

Toro

Ramos

et al. 1998

Biology of Reproduction

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“…These findings are similar to those reported for the rat [2,6,7] and pig [4] and support the hypothesis that rising concentrations of estrogen observed during late pregnancy establish an increased responsiveness of the cervix to RX. Although not well characterized, this action may be manifest as an increase in the number of receptors for RIX after exposure to estrogen [30] or in production of other humoral or enzymatic factors, such as prostaglandins or collagenase [11,31], that mediate or synergize with the actions of RIX. Finally, administration of P lessened the ability of RIX to promote cervical softening as compared to that in RLX-treated controls (EB + CO) and produced a distensibility response similar to that of RLX-treated gilts receiving no steroidal treatment (CO).…”

Section: Resultsmentioning

confidence: 96%

“…These findings are consistent with previous results in the rat [1,8,13,17] demonstrating that cervical content of collagen increased and cervical concentration of collagen decreased after administration of steroids and RIX. Some have hypothesized that RIX-induced changes in concentrations of GAGs and collagen, together with reorganization of the connective tissue framework [9], may serve as the biochemical basis for increased compliancy of the cervix at parturition [11,12,17].…”

Section: Discussionmentioning

confidence: 99%

“…This work was supported in part by USDA grant 89-37240-4772. the pig [10]. It has been hypothesized that these changes in the biochemical characteristics, collagen framework, and extracellular matrix of the cervical tissue represent the basis for reduction in tensile strength and increased distensibility of the cervix at the time of delivery of the young [11,12]. Some of the hormonal factors regulating the compositional and structural changes observed in cervical tissues during pregnancy and the periparturient period have been determined.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Ovarian Steroids on Relaxin-Induced Distensibility and Compositional Changes in the Porcine Cervix1

Hall

Anthony

1993

Biology of Reproduction

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A study was conducted to examine the influence of ovarian steroids on relaxin-induced changes in distensibility and composition of the uterine cervix in gilts. Ovariectomized, prepubertal gilts received (i.m.) either 1) 0.5 ml corn oil (CO) for 16 days; 2) 0.5 ml CO for 16 days and estradiol benzoate (EB; 200 micrograms) twice daily on Days 13-14; 3) EB on Days 0-1 followed by CO on Days 3-16 (EB + CO); 4) EB on Days 0-1 followed by CO on Day 2 and twice daily injections of 100 mg progesterone (P) on Days 3-16 (EB + P); or 5) EB on Days 0-1 followed by CO on Day 2 and P on Days 3-16 with additional EB treatment on Days 13-14 (EB + P + EB). One half of each group also received (i.m.) 0.5 ml 0.1 M PBS or 0.5 mg relaxin (RLX) every 6 h for 54 h coinciding with the final 2 days of the experimental period. Administration of RLX increased (p < 0.05) cervical distensibility compared to PBS treatment, with the response being greater (p < 0.05) in EB-, EB + CO-, and EB + P + EB-treated gilts compared to CO- or EB + P-treated gilts. Water content of cervical tissue was greater (p < 0.05) in EB-, EB+P- and EB + P + EB-treated gilts compared to CO- or EB + CO-treated gilt: and in all treatments, RLX enhanced (p < 0.05) imbibition of water by cervical tissues compared to that in PBS-treated gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Interpubic ligaments grow in preparation for parturition under the stimulus of increasing levels of estradiol and relaxin (37,39). However, this process also depends upon a decrease in serum progesterone, which antagonizes the effects of estradiol and relaxin on the pubic symphyseal connective tissue during pregnancy.…”

Section: Discussionmentioning

confidence: 99%

Hormonal Changes Accompanying Cigarette Smoke-Induced Preterm Births in a Mouse Model

Steinetz

Lasano

et al. 2006

Exp Biol Med (Maywood)

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Epidemiologic evidence indicates that maternal smoking increases the risk of preterm birth. While a number of plausible mechanisms for early delivery have been offered, the role of gestational hormones in this smoke-induced outcome is uncertain. Thus, a toxicologic study was performed to examine the effects and underlying hormonal mechanisms of mainstream cigarette smoke (MCS) exposure on gestational duration. Pregnant B6C3F1 mice were exposed by inhalation to MCS for 5 days/week (4 hrs/day) from Gestational Day (GD) 4 to parturition. Smoke-induced effects on gestational length, interpubic ligament length, maternal hormone secretion patterns (estradiol-17beta, progesterone, prolactin, and relaxin), body weight gain, postimplantation loss, litter size, and offspring sex ratio were examined. Dams exposed to MCS at a concentration equivalent to smoking less than one pack of cigarettes/day (carbon monoxide = 25 parts per million, total suspended particulates = 16 mg/m3) demonstrated a significant (P < 0.05) shortening of gestational duration (compared with pregnant, air-exposed mice). In addition, MCS-exposed mice sacrificed on GD 18 had significantly (P < 0.05) increased interpubic ligament length, elevated serum estrogen levels, and a reduced progesterone to estradiol-17beta ratio (compared with air-exposed controls); levels of progesterone and prolactin were only modestly decreased and increased, respectively, in the MCS-exposed mice. Smoke exposure had no significant effects on maternal relaxin levels, body weight gain, postimplantation loss, litter size, or sex ratio. Results of this study demonstrate that inhalation exposure of pregnant mice to a low dose of MCS shortens gestation and alters hormone secretory patterns, which are important for maintaining pregnancy and inducing parturition. These findings support the view that pregnant women who smoke (even modestly) may be at increased risk for preterm birth, and that early delivery may be related (at least partly) to MCS-induced.

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Speculations on the Probable Role of Relaxin in Cervical Dilation and Parturition in Rats

Cited by 8 publications

References 28 publications

Role of Relaxin and Estrogen in the Control of Eosinophilic Invasion and Collagen Remodeling in Rat Cervical Tissue at Term1

Role of Relaxin and Estrogen in the Control of Eosinophilic Invasion and Collagen Remodeling in Rat Cervical Tissue at Term1

Influence of Ovarian Steroids on Relaxin-Induced Distensibility and Compositional Changes in the Porcine Cervix1

Hormonal Changes Accompanying Cigarette Smoke-Induced Preterm Births in a Mouse Model

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