Effect of Diet-Induced Sodium Deficiency on Normal and Compensatory Growth of the Lung in Young Rats

Abstract

PNX , left pneumonectomy Sham, sham thoracotomy LW, dry lung weight BW, body weight Bronchopulmonary dysplasia is a co mmon form of pu lmon ary dysfun ction th at is observed in as man y as 20% of infants und er 1500 g birth weight ( I). It is now kn own th at the pathogenesis of chronic lun g disease in the neonatal period is related not only to the acute lun g inj ury, but also to th e ability of th e infa nt to heal adequ ately. Th is in turn is influenced to a great extent by nutrition al factors (2). Undernutrition increases the mortalit y rate of newborn rats exposed to hyperoxia (3), an d ma y perm anent ly affect lung struc ture. Rodent s deprived of food for the first 2 1 d have a permanent redu ction in th e number of lun g cells as assessed by lun g DNA measurement s and a permanent reduction in lun g RNA (4, 5).Electrolyte abnorma lities also are co m mo n in neonates, especially those with chronic cardiopulmonary distress. T hese in fants are often treated by restrict ing salt and water intake and administerin g di uretics (6)(7)(8), occasionally lead ing to sodium deficiency (9). Sodium deficiency has been associated with poor growth in both anima ls (10, II ) and hum ans (12) . Wassner (10) showed th at rats fed a diet deficien t in sodium dem onstrate delayed growth in term s of both weight gain and length, despite com parable caloric int ake. Thi s was associated with o nly mild hyponatremia ( 134 ve rsus 139 m mol/L) and with marked urinary sodium conservation. The NaD animals also had lower tissue RNA concentrations and exhibited decreased rates of skeletal mu scle pro tein synthesis relative to sodi um replete controls. Th is raises th e issue of whether cha nges in sodium balance may modul ate growth and development of the lun g.Parti al pneumon ectom y in th e young rat provides a welldescribed laboratory model of rapid lun g growth ( 13,14). After partial resection of th e lun g, th ere is a rapi d restorat ion of tissue mass so that the remaining lun g mass equals th at of both lun gs in Sham-operated animals (15 ). Increa sed total DNA in the right lung and norm al protein/DNA ratios, along with morph om etric stud ies (16), suggest that th is respo nse results from cellular hyperplasia rather th an hypert roph y. To determ ine th e influ ence of sodium balance on lun g growt h, the rate and exten t of compensatory growth of th e right lung after PNX was investigated in young rats fed an NaD but otherwise nutrition ally complete diet.Fou r-wk-old male Sprague-Daw ley rats weighing 83 ± I g (Char les River Laborat ories, Wilmi ngton, MA) were rand omly 455 Abbreviations NaD , sodium deficient Con, sodium-replete control ABSTRACT, Sodium deficiency is as sociated with decrea sed muscle growth and protein synthesis. We investigated the influence of diet-induced sodium deficiency on the rate and extent of compensatory growth of the right lung after left pneumonectomy in young rats of 83 ± 1 g body weight. Starting 1 wk before surgery, all rats were fed a diet deficient only in sodium (2-9 It...

The effect of sodium repletion on growth and protein turnover in sodium-depleted rats

“…By 5-504 6 days of salt supplementation, daily weight and length gain, percentage organ weights, muscle protein synthesis rates, muscle and liver RNA concentrations were all equivalent in the supplemented and control animals. In addition to the organs reported in this paper, there is preliminary evidence that salt depletion adversely affects the regeneration of lung tissue after pneumonectomy in young rats [18]. Thus, salt deficiency appears to have a global effect within the rat to decrease anabolism and limit growth.…”

Rethinking furosemide use for infants with bronchopulmonary dysplasia

“…The potential impact of furosemide on total body sodium homeostasis, cannot be overlooked. Sodium depletion negatively impacts energy efficiency, weight and linear growth and potentially lung growth and reparation 11‐14 . In rats, sodium deficiency impairs compensatory lung growth following pneumonectomy 14 .…”

“…Sodium depletion negatively impacts energy efficiency, weight and linear growth and potentially lung growth and reparation 11‐14 . In rats, sodium deficiency impairs compensatory lung growth following pneumonectomy 14 . If sodium deficiency impairs lung growth, differentiation and reparative processes in the developing lung, diuretic therapy may be counterproductive in infants with chronic lung disease.…”