CONICET | Buscador de Institutos y Recursos Humanos

Objective: Dehydration is an important cause of morbimortality in children. It is associated with higher blood pressure in adulthood. Nitric oxide (NO) is involved in fluid homeostasis. We have showed that changes in cardiovascular NO system in response to water deprivation were dependent on the age. Our aim was to evaluate the effects of osmotic stress triggered by water restriction on NO system and its impact on hemodynamic parameters in growing rats. Design and Method: male Sprague-Dawley 25 and 50 days old rats were divided into (n = 10 each group): R: water restriction during 3 days; C: water ad libitum for 3 days. At the end of each experiment, we determined: hematocrit, body weight, plasma osmolality , systolic blood pressure (SBP) and heart rate (HR); animals were then sacrificed to evaluate in right atrium and left ventricle NO synthase (NOS) protein levels (Western Blot) and activity (conversion of [14C]-L-Arginine to [14C]-L-Citrulline). Results: NOS protein levels were higher in the left ventricle of C50 compared to pups. NOS isoforms protein levels were increased in response to dehydration in both age groups, except for iNOS in the youngest group. In the right atrium, eNOS and iNOS protein levels were similar between the two age groups and nNOS protein levels were higher in the youngest group. In response to dehydration, eNOS and nNOS were decreased in the C25, without changes in iNOS protein levels. In the oldest group, no differences were observed in nNOS or iNOS, and eNOS was decreased. Conclusion: Water restriction induced a hypovolemic state in both age groups. The cardiac NO pathway would participate differentially in the response to osmotic stress, according to the studied tissue and the stage of postnatal growth.