Effects of pre- and postnatal protein deprivation on atrial natriuretic peptide- (ANP-) granules of the right auricular cardiocytes

Abstract

The atrial natriuretic peptide (ANP) is a peptide hormone that is mainly produced in the cardiocytes of the atria and auricles, where it is stored within secretory granules. The aim of the present work was to analyze the effects of pre- and postnatal protein malnutrition on weight gain, the size of the heart and the number and sizes of the ANP-granules in the cardiocytes of the rat's right auricle. This study was conducted on 21-day-old rats from mothers exposed to 73% protein restriction during the gestation and lactation and on age-matched control animals. At this stage, both control and protein-deprived animals were killed by a lethal intraperitonial injection of sodic pentobarbital. The weight and the size of the heart were determined and ANP-granules of auricular cardiocytes were examined by transmission electron microscopy and ultrastructural morphometry. Protein deprivation of the mother throughout pregnancy, and the mother and unweaned rat pups in the first 21 postnatal days reduced the weights of pups to about 60% of the normally fed group. The weight and size of the heart were also reduced, by about 50%. Despite this, perinatal malnutrition did not significantly affect the numbers of ANP-granules/field in the cardiocytes. However, there was a small but significant reduction in the sizes of granules. It is concluded that ANP-granules are protected from loss even when there is a substantial reduction in body weight and organ size caused by protein deprivation.