• Gabriel Dimitriou, Despina Papakonstantinou, Eleana F Stavrou, Sotirios Tzifas, Aggeliki Vervenioti, Anny Onufriou, Aglaia Athanassiadou, and Stefanos Mantagos.
• Neonatal Intensive Care Unit, Department of Pediatrics, University of Patras Medical School, Rio, Patras, Greece. gdimitriou@med.upatras.gr
• Resp Res. 2010 Jan 1;11:57.

BackgroundAngiotensin converting enzyme (ACE) gene contains a polymorphism, consisting of either the presence (I) or absence (D) of a 287 base pair fragment. Deletion (D) is associated with increased circulating ACE (cACE) activity. It has been suggested that the D-allele of ACE genotype is associated with power-oriented performance and that cACE activity is correlated with muscle strength. Respiratory muscle function may be similarly influenced. Respiratory muscle strength in infants can be assessed specifically by measurement of the maximum inspiratory pressure during crying (Pimax). Pressure-time index of the respiratory muscles (PTImus) is a non-invasive method, which assesses the load to capacity ratio of the respiratory muscles.The objective of this study was to determine whether increased cACE activity in infants could be related to greater respiratory muscle strength and to investigate the potential association of cACE with PTImus measurements as well as the association of ACE genotypes with cACE activity and respiratory muscle strength in this population.MethodsSerum ACE activity was assayed by using a UV-kinetic method. ACE genotyping was performed by polymerase chain reaction amplification, using DNA from peripheral blood. PTImus was calculated as (Pimean/Pimax) x (Ti/Ttot), where Pimean was the mean inspiratory pressure estimated from airway pressure, generated 100 milliseconds after an occlusion (P0.1), Pimax was the maximum inspiratory pressure and Ti/Ttot was the ratio of the inspiratory time to the total respiratory cycle time. Pimax was the largest pressure generated during brief airway occlusions performed at the end of a spontaneous crying effort.ResultsA hundred and ten infants were studied. Infants with D/D genotype had significantly higher serum ACE activity than infants with I/I or I/D genotypes. cACE activity was significantly related to Pimax and inversely related to PTImus. No association between ACE genotypes and Pdimax measurements was found.ConclusionsThese results suggest that a relation in cACE activity and respiratory muscle function may exist in infants. In addition, an association between ACE genotypes and cACE activity, but not respiratory muscle strength, was demonstrated.

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