A BIOCHEMICAL-MORPHOLOGICAL STUDY ON MICROVILLUS PLASMA-MEMBRANE DEVELOPMENT

The microvillus plasma membrane of the human placental syncytiotrophob last at term has been extensively studied, while little is known about the characteristics of its development. The aim of the present work w as to compare functional and structural properties of this membrane at early and term gestational age. Ten normal term placentas (40 weeks) and ten placentas at 10 weeks of gestational age were studied. The Na/K+-ATPase activity is significantly decreased in the syncytiotrophobl ast plasma membrane obtained from term placentas as compared to the ea rly ones, with significant variation of maximum velocity (V-max). The microviscosity, evaluated try the P parameter of DPH and S-n parameter s of 5- and 16-NS, is increased in the term placentas compared to the early placentas. This alteration is accompanied by an increased choles terol to phospholipids ratio in term placentas, while there is a decre ased unsaturated to saturated fatty acid ratio. As follows from morpho logical studies, an increased mean diameter in the E face was observed in the term placenta with respect to the early placenta. The distribu tion factor DF, wich indicates the particle aggregation state, decreas ed in the E face in the term placenta as compared to the early one. Th e present biochemical morphological study shows that a deep modificati on of the membrane is at the basis of the syncytiotrophoblast plasma m embrane development.