Lung morphometric and functional changes in canine neonates after prenatal corticoterapy

Author(s)

Fernanda Machado Regazzi

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2011-11-30

Examining board members

Camila Infantosi Vannucchi; Francisco Javier Hernandez Blazquez; Celso Moura Rebello

• Advisor: Camila Infantosi Vannucchi

Abstract

The final gestational period is marked by an important processes that characterize the lung fetal maturation, like structural changes such as expansion of the areas of gas exchange, and functional changes, such as increased production of surfactant, whose main function is to reduce the surface tension in the air-liquid interface alveolar, preventing the alveoli from collapsing during late expiration. Studies in different species indicate the influence of endocrine factors, including glucocorticoids in fetal lung development and transition to extrauterine life. Up till now, there is not studies in dogs, with the primary objective to evaluate the action of maternal corticosteroid therapy in improving lung function. Thus, the objectives of this study was to identify morphological changes in lung function in preterm and terms neonates submitted to prenatal maternal corticosteroids and correlate them to the improvement in lung function during the neonatal period. For it 25 canine neonates, born by scheduled cesarean section, were randomly divided into 2 groups: control group (CONT) (no maternal corticosteroid therapy, n = 15) and Group betamethasone (BETA) (maternal corticosteroid therapy at 55 days gestation; n = 10), by application of betamethasone (Celestone Chronodose Injection ®) in a single dose of 0.5 mg / kg of maternal weight, route of administration by intra-muscular (IM). Control group neonates were evaluated at 55, 57 and 63 days of gestation, and the betamethasone group, at 58 and 57 days of gestation. The clinical assessment was made by Apgar score, blood gas and pulmonary radiography. Still, the structural and functional lung changes were verified by morphometric analysis and immunohistochemistry to detect the number of type II pneumocytes producers surfactant protein B (SP-B) in the lung parenchyma. There was better clinical outcome in the groups BETA 57 at 60 minutes of life. The values of heart rate were significantly higher in term treatment and control groups compared to the group CONT 57. The score of respiratory frequency and pattern was statistically higher in groups BETA 57 e 63 followed by the group BETA 58. Statistically similar reflex irritability were observed between the treated groups and term. From birth to 60 minutes of life there was not statistical difference in the assessment of muscle tone between the groups, with significantly higher values at 240 minutes of life in term treatment and control groups. Neonates of CONT 63 has mucous apparent assessment of Apgar statistically superior to other groups at birth, with values statistically equal to tratads and group CONT 57 at 60 minutes of life. At birth and after 2 hours of life, all neonates had acidemia, with better compensatory response to acid-base balance in the group BETA 58. There was an increased septation in treated and control groups comparing other groups. A statistically higher percentage of alveolarization was observed in group CONT 63, followed by the group BETA 58. A lower percentage of saccules was identified in the group CONT 63 followed by groups BETA 57 and CONT 55. There was not statistical differences in the number of type II pneumocytes marked for protein SP-B between the treated groups and CONT 57. The radiographic evaluation showed a lower percentage of air bronchogram, and atelectasis in the group BETA 57, associated with better visualization of the pulmonary parenchyma. In conclusion, maternal administration of betamethasone in prenatally period induced structural changes of the lung parenchyma, resulting in higher values of Apgar score. There was greater compensatory response in the treated groups, the reflex of an increase capacity of pulmonary gas exchange. It was not possible to indentify increases synthesis of surfactant between the groups in response to prenatal administration of betamethasone. (AU)

• FAPESP's process: 09/06752-9 - FUNCTIONAL AND MORPHOMETRICAL LUNG CHANGES OF CANINE NEONATES UNDER ANTENATAL CORTICOTHERAPY.
• Grantee: Fernanda Machado Regazzi
• Support Opportunities: Scholarships in Brazil - Master