Endothelin-1 pulmonary vasoconstriction in rats with diaphragmatic hernia

Congenital diaphragmatic hernia-associated pulmonary hypertension

Congenital diaphragmatic hernia (CDH) is a neonatal pathology in which intrathoracic herniation of abdominal viscera via diaphragmatic defect results in aberrant pulmonary and cardiovascular development. Despite decades of study and many advances in the diagnosis and treatment of CDH, morbidity and mortality remain high, largely due to pulmonary hypertension (PH), along with pulmonary hypoplasia and cardiac dysfunction. In patients with CDH, hypoplastic pulmonary vasculature and alterations in multiple molecular pathways lead to pathophysiologic pulmonary vasculopathy and, for severe CDH, sustained, elevated pulmonary arterial pressures. This review addresses the multiple anatomic and physiologic changes that underlie CDH-associated PH (CDH-PH), along with the multimodal treatment strategies that exist currently and future therapies currently under investigation.

Pulmonary hypertension secondary to congenital diaphragmatic hernia: factors and pathways involved in pulmonary vascular remodeling

Congenital diaphragmatic hernia (CDH) is a severe birth defect that is characterized by pulmonary hypoplasia and pulmonary hypertension (PHTN). PHTN secondary to CDH is a result of vascular remodeling, a structural alteration in the pulmonary vessel wall that occurs in the fetus. Factors involved in vascular remodeling have been reported in several studies, but their interactions remain unclear. To help understand PHTN pathophysiology and design novel preventative and treatment strategies, we have conducted a systematic review of the literature and comprehensively analyzed all factors and pathways involved in the pathogenesis of pulmonary vascular remodeling secondary to CDH in the nitrofen model. Moreover, we have linked the dysregulated factors with pathways involved in human CDH. Of the 358 full-text articles screened, 75 studies reported factors that play a critical role in vascular remodeling secondary to CDH. Overall, the impairment of epithelial homeostasis present in pulmonary hypoplasia results in altered signaling to endothelial cells, leading to endothelial dysfunction. This causes an impairment of the crosstalk between endothelial cells and pulmonary artery smooth muscle cells, resulting in increased smooth muscle cell proliferation, resistance to apoptosis, and vasoconstriction, which clinically translate into PHTN.

Changes in vasoactive pathways in congenital diaphragmatic hernia associated pulmonary hypertension explain unresponsiveness to pharmacotherapy

BACKGROUND

Patients with congenital diaphragmatic hernia (CDH) have structural and functional different pulmonary vessels, leading to pulmonary hypertension. They often fail to respond to standard vasodilator therapy targeting the major vasoactive pathways, causing a high morbidity and mortality. We analyzed whether the expression of crucial members of these vasoactive pathways could explain the lack of responsiveness to therapy in CDH patients.

METHODS

The expression of direct targets of current vasodilator therapy in the endothelin and prostacyclin pathway was analyzed in human lung specimens of control and CDH patients.

RESULTS

CDH lungs showed increased expression of both ETA and ETB endothelin receptors and the rate-limiting Endothelin Converting Enzyme (ECE-1), and a decreased expression of the prostaglandin-I₂ receptor (PTGIR). These data were supported by increased expression of both endothelin receptors and ECE-1, endothelial nitric oxide synthase and PTGIR in the well-established nitrofen-CDH rodent model.

CONCLUSIONS

Together, these data demonstrate aberrant expression of targeted receptors in the endothelin and prostacyclin pathway in CDH already early during development. The analysis of this unique patient material may explain why a significant number of patients do not respond to vasodilator therapy. This knowledge could have important implications for the choice of drugs and the design of future clinical trials internationally.

Congenital diaphragmatic hernia-associated pulmonary hypertension

Congenital diaphragmatic hernia (CDH) is a complex entity wherein a diaphragmatic defect allows intrathoracic herniation of intra-abdominal contents and both pulmonary parenchymal and vascular development are stifled. Pulmonary pathology and pathophysiology, including pulmonary hypoplasia and pulmonary hypertension, are hallmarks of CDH and are associated with disease severity. Pulmonary hypertension (PH) is sustained, supranormal pulmonary arterial pressure, and among patients with CDH (CDH-PH), is driven by hypoplastic pulmonary vasculature, including alterations at the molecular, cellular, and tissue levels, along with pathophysiologic pulmonary vasoreactivity. This review addresses the basic mechanisms, altered anatomy, definition, diagnosis, and management of CDH-PH. Further, emerging therapies targeting CDH-PH and PH are explored.

Increased pulmonary RhoA expression in the nitrofen-induced congenital diaphragmatic hernia rat model

PURPOSE

Persistent pulmonary hypertension remains a major cause of mortality and morbidity in cases of congenital diaphragmatic hernia (CDH). Recently, RhoA/Rho-kinase-mediated vasoconstriction has been reported to be important in the pathogenesis of pulmonary hypertension (PH). Several recent reports have described that fasudil, a potent Rho-kinase inhibitor and vasodilator, could represent a potential therapeutic option for PH. We designed this study to investigate the hypothesis that the expression level of RhoA is increased in the nitrofen-induced CDH rat model. The expression level of Wnt11, an activator of RhoA, was also evaluated.

METHODS

Pregnant rats were treated with or without nitrofen on gestational day 9 (D9). Fetuses were sacrificed on D17, D19 and D21 and were divided into control and CDH groups. Quantitative real-time polymerase chain reaction was performed to determine the pulmonary gene expression levels of both Wnt11 and RhoA. An immunofluorescence study was also performed to evaluate the expression and localization of RhoA.

RESULTS

The relative mRNA expression levels of pulmonary Wnt11 and RhoA on D21 were significantly increased in the CDH group compared with the control group (p=0.016 and p=0.008, respectively). The immunofluorescence study confirmed the overexpression of RhoA in the pulmonary vessels of CDH rats on D21.

CONCLUSIONS

Our results provide evidence that the RhoA/Rho-kinase-mediated pathway is involved in the pathogenesis of PH in the nitrofen-induced CDH rat model. Our data also suggest that the fasudil, a Rho-kinase inhibitor, could represent a therapeutic option for the treatment of PH in CDH.

Understanding and treating pulmonary hypertension in congenital diaphragmatic hernia

Lung hypoplasia and pulmonary hypertension are classical features of congenital diaphragmatic hernia (CDH) and represent the main determinants of survival. The mechanisms leading to pulmonary hypertension in this malformation are still poorly understood, but may combine altered vasoreactivity, pulmonary artery remodeling, and a hypoplastic pulmonary vascular bed. Efforts have been directed at correcting the "reversible" component of pulmonary hypertension of CDH. However, pulmonary hypertension in CDH is often refractory to pulmonary vasodilators. A new emerging pattern of late (months after birth) and chronic (months to years after birth) pulmonary hypertension are described in CDH survivors. The true incidence and implications for outcome and management need to be confirmed by follow-up studies from referral centers with high patient output. In order to develop more efficient strategies to treat pulmonary hypertension and improve survival in most severe cases, the ultimate therapeutic goal would be to promote lung and vascular growth.

[Possible responsibility of EDNRA gene triplication, coding for the endothelin 1 ET-A receptor in a case of congenital diaphragmatic hernia]

Congenital diaphragmatic hernia has a physiopathology unfully understood, and is the cause of an important morbimortality. We report the case of a fetus suffering from a diaphragmatic hernia associated with a EDNRA gene triplication, coding for the endothelin 1 receptor. High-resolution genetic techniques were able to find the possible origin of this pathology, and showed that it was an isolated form with a good prognostic. ET-A receptor over-expression in lung vessels may cause a vascular remodeling and a lung arterial high blood pressure. This lung abnormality would have occurred before the diaphragmatic defect.

Looking beyond PPHN: the unmet challenge of chronic progressive pulmonary hypertension in the newborn

Abstract Infants with forms of pulmonary hypertension (PH) that persist or develop beyond the first week of life are an understudied group of patients with up to 40%-60% mortality. The clinical management of the progressive PH that develops in these infants is challenging because of the nonspecific signs and symptoms of clinical presentation, the limited diagnostic sensitivity of standard echocardiographic techniques, and the lack of proven therapies. The signaling mechanisms that underlie the structural and functional abnormalities in the pulmonary circulation of these infants are not yet clear. The ability to improve outcomes for these patients awaits technological advances to improve diagnostic capabilities and therapeutic discoveries made in basic science laboratories that can be tested in randomized clinical trials.

Upregulation of endothelin receptors A and B in the nitrofen induced hypoplastic lung occurs early in gestation

PURPOSE

Pulmonary hypoplasia and persistent pulmonary hypertension (PPH) aggravate clinical courses in congenital diaphragmatic hernia (CDH). Endothelin 1 enhances PPH by vasoconstriction and proliferation of vessel walls. Up-regulation of pulmonary Endothelin Receptors A and B (EDNRA, EDNRB) has been reported in human CDH and animal models, but the onset of those alterations during lung development remains unclear. We hypothesized that pulmonary expression of EDNRA and EDNRB is up-regulated at early gestational stages in the nitrofen model.

METHODS

Pregnant rats were exposed to nitrofen or vehicle on gestational day 9 (D9). Embryos were sacrificed on D15, D18 and D21 and divided into nitrofen- and control group. Pulmonary RNA was extracted and mRNA levels of EDNRA and EDNRB were determined by real-time PCR. Immunohistochemistry for protein expression of both receptors was performed.

RESULTS

mRNA levels of EDNRA and EDNRB were significantly increased in the nitrofen group on D15, D18 and D21. Immunohistochemistry revealed increased pulmonary vascular expression of EDNRA and EDNRB compared to controls.

CONCLUSION

Altered expression of EDNRA and EDNRB is an early event in lung morphogenesis in the nitrofen model. We speculate that pulmonary arteries in CDH become excessively muscularised in early fetal life, becoming unable to adapt normally at birth.

Modulating effect of a selective endothelin A receptor antagonist on pulmonary endothelin system protein expression in experimental diaphragmatic hernia

BACKGROUND/PURPOSE

Previously, we reported that perinatal administration of atrasentan, a selective endothelin A receptor (ETA) antagonist, provided a beneficial effect on the cardiopulmonary profile under short-term conditions in newborn lambs with surgically induced congenital diaphragmatic hernia (CDH). We hypothesized that changes in the hemodynamic profile that we observed at birth in treated animals could be influenced by pulmonary modulation of the endothelin (ET) system.

METHODS

The effect of atrasentan on protein expression levels of ETs and ET receptors (ETA and ETB receptor) was investigated by immunohistochemistry in lung tissues of untreated control (n = 3), treated control (n = 6), untreated CDH (n = 6), and treated CDH newborn lambs (n = 8).

RESULTS

Right lung tissue of treated control lambs showed significantly higher ETA protein expression levels in both vascular adventitia and airway epithelia when compared with that of untreated control lambs (P < .05). In contrast, protein expression levels of ETA and ETB receptor were significantly lower in the vascular smooth muscle cells among other tissue subcompartments of the right lung of treated CDH newborn lambs vs CDH lambs (P < .02 and P = .005, respectively).

CONCLUSIONS

We speculate that rapid pulmonary modulation of ET system protein expression levels by atrasentan results from an indirect effect possibly dependent on ventilation and/or perfusion. In CDH groups, this could contribute to the beneficial effect of the treatment.

Effect of temporary tracheal occlusion on the endothelin system in experimental cases of diaphragmatic hernia

Previously, the authors have shown that tracheal occlusion (TO) partially reverses the onset of congenital diaphragmatic hernia (CDH)-induced pulmonary hypertension (PH) and abnormal pulmonary vascular development whereas release of the occlusion (TR) abolishes these clinical benefits. As a consequence of their mitogenic and vasoactive properties, the authors hypothesize that the expression of endothelin (ET)-1 and ET receptor (ETA) genes is increased in lungs of CDH lambs, and that this increase is abolished partially in CDH + TO but not in CDH + TO + TR. A surgical left-sided CDH was created in fetal lambs at 80 days of gestation (gd), followed by TO at 108 gd, and by TR at 129 gd. Four groups were compared: CDH, CDH + TO, CDH + TO + TR, and nonoperated controls (C). Assessment of mRNA expression by Northern blot showed significantly lower ET-1 and ETA levels in the CDH group than in the CDH + TO +/- TR groups (P < .05). Endothelin protein expression levels were lower in CDH +/- TO +/- TR groups when compared with controls for airways and vessels (P < .05) with the exception of endothelial cells. In contrast, ETA protein expression levels were higher in CDH +/- TO +/- TR groups compared with controls for airways and blood vessels smooth muscles (P < .05). These results suggest that involvement of the endothelin system in the pulmonary hypertension associated with CDH is limited. However, the endothelin system appears to be modulated during development.

Congenital diaphragmatic hernia: searching for answers

BACKGROUND

Pulmonary hypoplasia and hypertension are the primary causes of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). At present, the origin of CDH and the causes of pulmonary hypoplasia and hypertension are unknown.

DATA SOURCES

This article reviews the available published data regarding the origin of CDH and the pathogenesis of the associated pulmonary hypertension and hypoplasia. These investigations have employed human tissues as well as two types of CDH animal models.

CONCLUSIONS

Investigations performed to date have not yet provided definitive answers regarding the pathogenesis of CDH. However, they have yielded many new and exciting discoveries and several opportunities for intervention. Ongoing research should open new possibilities to improve the outcome for these unfortunate babies with CDH.

The endothelin system in pulmonary hypertension

Pulmonary hypertension (PH) may result from numerous clinical entities affecting the pulmonary circulation primarily or secondarily. It is recognized that vascular endothelial dysfunction contributes to the development and perpetuation of PH by creating an imbalance between vasodilating and antiproliferative forces and between vasoconstrictive and proliferative forces. In that context, endothelin-1 (ET-1) overproduction was rapidly targeted as a plausible contributor to the pathogenesis of PH. The lung is recognized as the major site for ET production and clearance. In all animal models of PH studied, circulating plasma ET-1 levels are elevated, accompanied by an increase in lung tissue expression of the peptide. The use of selective ETA and dual ETA-ETB receptor antagonists in these models both in prevention and in therapeutic studies have confirmed the contribution of ET-1 to the rise in pulmonary vascular tone, pulmonary medial hypertrophy, and right ventricular hypertrophy. This is found consistently in models affecting the pulmonary circulation primarily or producing PH secondarily. Recent clinical trials in patients with pulmonary arterial hypertension have confirmed the therapeutic effectiveness of ET-receptor antagonists in humans. We offer a systematic review of the pathogenic role of the ET system in the development of PH as well as the rationale behind the preclinical and ongoing clinical trials with this new class of agents.

Airway smooth muscle changes in the nitrofen-induced congenital diaphragmatic hernia rat model

In the fetal rat, nitrofen induces congenital diaphragmatic hernia (CDH) and pulmonary vascular remodeling similar to what is observed in the human condition. Airway hyperactivity is common in infants with CDH and attributed to the ventilator-induced airway damage. The purpose of this study was to test the hypothesis that airway smooth muscle mechanical properties are altered in the nitrofen-induced CDH rat model. Lungs from nitrofen-exposed fetuses with hernias (CDH) or intact diaphragm (nitrofen) and untreated fetuses (control) were studied on gestation d 21. The left intrapulmonary artery and bronchi were removed and mounted on a wire myograph, and lung expression, content, and immunolocalization of cyclooxygenases COX-1 and COX-2 were evaluated. Pulmonary artery muscle in the CDH group had significantly (p < 0.01) lower force generation compared with control and nitrofen groups. In contrast, the same generation bronchial smooth muscle of the CDH and nitrofen groups developed higher force compared with control. Whereas no differences were found in endothelium-dependent pulmonary vascular muscle tone, the epithelium-dependent airway muscle relaxation was significantly decreased (p < 0.01) in the CDH and nitrofen groups. The lung mRNA levels of COX-1 and COX-2 were increased in the CDH and nitrofen groups. COX-1 vascular and airway immunostaining, as well as COX-1 and COX-2 lung protein content, were increased in the CDH group. This is the first report of airway smooth muscle abnormalities in the nitrofen-induced fetal rat model of CDH. We speculate that congenital airway muscle changes may be present in the human form of this disease.

Nitrofen inhibition of pulmonary growth and development occurs in the early embryonic mouse

BACKGROUND/PURPOSE

It was believed previously that pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) was a consequence of the herniation of abdominal viscera into the chest. Using the murine nitrofen-induced model of CDH, the authors evaluated lung growth and development before diaphragm closure or herniation.

METHODS

The authors examined nitrofen-exposed early embryonic lungs on embryonic day 12 (E12). Branching morphogenesis was quantified before and after 4 days in culture in serumless chemically defined media and compared with age-matched control lungs. The mRNA expression of proliferative and developmental markers in cultured lungs was then determined.

RESULTS

Nitrofen-exposed lungs had 30% fewer total terminal branches than age-matched controls (9.3 +/- 1.9 nitrofen v 13.7 +/- 2.6 control; P <.001). Hypoplasia also was more profound in the left than the right lung. These effects persisted after culturing the lungs for 4 days in serumless chemically-defined media (31.7 +/- 6.8 nitrofen v 42.9 +/- 8.4 control, P <.001). Furthermore, the mRNA expression of proliferative and developmental markers was decreased in nitrofen-exposed E12 lungs cultured for 4 days (as a percentage of age-matched controls): cyclin A (69.28%; P =.04), Nkx2.1 (44.4%, 0.04), SP-A (24.1%; P =.008), SP-B (23.4%; P =.05), SP-C (20%; P =.06), and CC-10 (13.8%; P =.04).

CONCLUSION

Nitrofen induces primary pulmonary hypoplasia and immaturity in the early embryonic mouse, and this effect persists in culture.

Effect of ABT-627 (A-147627), a potent selective ET(A) receptor antagonist, on the cardiopulmonary profile of newborn lambs with surgically-induced diaphragmatic hernia

1. Postnatal mortality in isolated congenital diaphragmatic hernia (CDH) is mainly related to the associated pulmonary hypertension (PH) and to right-to-left shunting. 2. Endothelins (ETs) are potent vasoconstrictors and pro-mitogenic peptides. Strong evidences support their participation in CDH and in the etiology of PH via the activation of ET(A) receptors (ET(A)-Rs). 3. Evaluation of the effect of ABT-627, a selective non-peptidic ET(A)-R antagonist, given from -15 to 210 min post-delivery (1 mg kg(-1) bolus +0.01 mg kg(-1) h(-1) infusion, i.v.), was conducted in the lamb model of CDH. 4. Severity of CDH was assessed in comparison to untreated controls (n=5). Untreated CDH lambs (n=7) had a higher mean pulmonary arterial pressure (MPAP; P<0.0001), lower mean blood pressure (MBP; P=0.0004), higher MPAP / MBP ratio (P<0.0001), lower arterial pH (P<0.0001), higher paCO(2) (P<0.0001), lower paO(2) (P<0.0001) and lower post-ductal pulsatile SaO(2) (P<0.0001) than untreated controls. 5. Treated controls (n=7) showed a higher MPAP, lower MBP, higher MPAP/MBP ratio, lower arterial pH, higher paCO(2), lower paO(2), lower post-ductal pulsatile SaO(2) and lower plasmatic ir-ET ratios compared to untreated controls (P<0.0001). 6. Treated CDH lambs (n=8) showed a higher MBP (P<0.0001), lower MPAP / MBP ratio (P<0.0001), higher arterial pH (P<0.0001), lower paCO(2) (P<0.0001), higher paO(2) (P=0.0228), higher post-ductal pulsatile SaO(2) (P=0.0016) and lower plasmatic ir-ET ratios (P=0.0247) when compared to untreated CDH lambs. 7. These observations revealed that, although acute perinatal treatment with a selective non-peptidic ET(A)-R antagonist had some adverse effects in controls, it attenuated the progressive cardiopulmonary deterioration that occurred after birth in CDH lambs.

Oxygen-induced vasodilation is blunted in pulmonary arterioles from fetal rats with nitrofen-induced congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Persistent pulmonary hypertension contributes to the high mortality rate associated with congenital diaphragmatic hernia (CDH). Oxygen is an important stimulus for pulmonary vasodilation in the perinatal period. The authors have investigated the responses of isolated pulmonary arterioles from fetal rats with and without CDH to an increase in oxygen tension.

METHODS

CDHs were induced in fetal rats by feeding nitrofen to timed-pregnant rats at midgestation. A third-generation pulmonary arteriole was isolated from the right lung at term. Isolated arterioles were pressurized at their "optimal distending pressure." Diameter changes in response to an increase in oxygen tension from 25 to 40 mm Hg ("hypoxic" conditions) to 90 to 150 mm Hg ("normoxic" conditions) were recorded for K(+) preconstricted arterioles from control rats, from rats with nitrofen-induced CDH, and from rats that were nitrofen exposed but did not have a CDH.

RESULTS

"Normoxic" exposure reversed the K(+) preconstriction in control arterioles by 124 +/- 26%. In contrast, arterioles from rats with nitrofen-induced CDH dilated significantly less than controls (20 +/- 15% of the K(+) preconstriction). The responses of arterioles from rats that were nitrofen exposed but did not get a CDH were not different (P >.05) from controls.

CONCLUSIONS

Oxygen-induced vasodilation is blunted in pulmonary arterioles from rats with nitrofen-induced CDH. Blunted oxygen-induced vasodilation may contribute to persistent pulmonary hypertension in CDH. J Pediatr Surg 36:593-597.

Lung hypoplasia in the nitrofen model of congenital diaphragmatic hernia occurs early in development

The teratogen nitrofen produces a congenital diaphragmatic hernia (CDH) and pulmonary hypoplasia in rodent fetuses that closely parallel observations made in humans. We hypothesized that these changes may be due to primary pulmonary hypoplasia and not herniation of the abdominal contents. Timed-pregnant rats were given nitrofen on day 9, and fetuses were harvested on days 13 through 21. Initial evagination of lung buds on gestational day 11 was not delayed in nitrofen-treated fetuses. On gestational day 13, however, there was a significant decrease in the number of terminal end buds in the lungs of nitrofen-exposed fetuses vs. controls. Thymidine-labeled lung epithelial and mesenchymal cells were significantly decreased in nitrofen-treated lungs. Lungs from nitrofen-treated fetuses exhibited wide septae with disorganized, compacted tissue, particularly around the air spaces. Expression of surfactant protein B and C mRNAs was significantly decreased in the nitrofen litters. In situ hybridization of fetal lung tissue at all gestational ages showed no difference in the expression of vascular endothelial growth factor, Flk-1, or Flt-1 mRNAs. Because closure of the diaphragm is completed on gestational day 16 in the rat, our results suggest that lung hypoplasia in this model of CDH is due at least in part to a primary effect of nitrofen on the developing lung.

ET(A)-receptor blockade and ET(B)-receptor stimulation in experimental congenital diaphragmatic hernia

The aim of this study was to assess the role of nitric oxide (NO) and endothelin (ET)-1 in the pathophysiology of persistent pulmonary hypertension of the newborn in fetal lambs with a surgically created congenital diaphragmatic hernia (CDH). The pulmonary vascular response to various agonists and antagonists was assessed in vivo between 128 and 132 days gestation. Age-matched fetal lambs served as control animals. Control and CDH lambs had similar pulmonary vasodilator responses to acetylcholine, sodium nitroprusside, zaprinast, and dipyridamole. The ET(A)-receptor antagonist BQ-123 caused a significantly greater pulmonary vasodilatation in CDH than in control animals. The ET(B)-receptor agonist sarafotoxin 6c induced a biphasic response, with a sustained pulmonary vasoconstriction after a transient pulmonary vasodilatation that was not seen in CDH animals. We conclude that the NO signaling pathway in vivo is intact in experimental CDH. In contrast, ET(A)-receptor blockade and ET(B)-receptor stimulation significantly differed in CDH animals compared with control animals. Imbalance of ET-1-receptor activation favoring pulmonary vasoconstriction rather than altered NO-mediated pulmonary vasodilatation is likely to account for persistent pulmonary hypertension of the newborn in fetal lambs with a surgically created CDH.

Effect of CGS 26303, an endothelin-converting enzyme-neutral endopeptidase inhibitor, on nitrofen-induced congenital diaphragmatic hernia in the rat

BACKGROUND/PURPOSE

The pathophysiology of congenital diaphragmatic hernia (CDH) associated with lung hypoplasia and pulmonary hypertension is not understood fully. Endothelins (ETs) are the most potent vasoconstrictors that also act as promitogenic agents. They may play a role during pregnancy in leading to the condition found at birth and ongoing mortality in CDH. Therefore, the authors studied the effect of CGS 26303, a nonselective endothelin-converting enzyme and neutral endopeptidase inhibitor, in the rat model of CDH.

METHODS

Pregnant Sprague-Dawley rats were divided into 3 groups: group 1 (n = 4) received CGS 26303 (50 mg/kg, subcutaneously, twice a day), from gestational day 12 until term (21 to 23 days); group 2 (n = 8) received nitrofen (100 mg/kg, orally) at gestational day 11.5; group 3 (n = 8) received both nitrofen and CGS 26303. The survival of the newborn rats was monitored up to 240 minutes. After natural death or euthanasia, they were weighed and microdissected. The degree of hernia was quantified as small, moderate, or severe, and lungs and liver were harvested and weighed.

RESULTS

Newborn rats from mothers of group 3 (n = 81) survived 196 +/- 8 minutes compared with 173 +/- 9 minutes of those of group 2 (n = 97). Severe CDH from group 3 (n = 20) had a mean survival time of 66 +/- 13 minutes compared with 26 +/- 4 minutes for those of group 2 (n = 27). Lung index in severe CDH pups of group 3 was increased by 13% compared with those from group 2 (P < .0001), whereas their liver index went down by 8% (P < .05).

CONCLUSIONS

These results suggest that CGS 26303 might have a beneficial effect when given during pregnancy in increasing survival at birth and reducing the severity of the pulmonary hypoplasia in newborn rats with nitrofen-induced CDH.