COMPARISON OF PLACENTAS FROM TWO SOCIOECONOMIC GROUPS. II. BIOCHEMICAL CHARACTERISTICS

Abstract

By comparison with placentas from an urban North American (Boston) population, those from an urban Central American (Guatemala City) series were significantly deficient in trophoblastic and fibroblastic mass. The total amounts of DNA, RNA, protein and alkaline phosphatase also tended to be reduced in these placentas, but only in the case of DNA did the difference approach significance. In vitro protein synthetic capacity per unit of RNA was not different in the two groups, although this proportion of ribosomes recovered as polysomes was lower in the Guatemalan series. On analyzing the data according to length of gestation, weight of child and weight of placenta, the only unequivocal relationship was that between the weight of the child and placental composition. There was a positive correlation between the weight of the child and the total amount of DNA, RNA, and protein in the placentas of each group. The placentas of low birth weight children in Guatemala tended to have relatively more small cells (less RNA and protein per cell) than in Boston. The placentas of children of large size in Guatemala showed smaller increase in cell number (less DNA) but cells appeared to be larger (more RNA and protein per cell). Protein synthetic capacity increased with increasing weight of the child at birth, and was of similar intensity in both series.