A histochemical investigation of the concept of placental insufficiency

ABSTRACT

This thesis is an account of some histochemical characteristics of placental tissue and their relationships to ageing and possibly to conditions associated with placental insufficiency. The introduction is a review of the clinical, experimental, and anatomical evidence for the concept of placental insufficiency. Using histochemical methods, the distribution and quantities of 10 enzymes were studied in 91 placentae representing normal and various types of abnormal pregnancies. Alkaline phosphatase and glucose - 6 - phosphatase showed a rising concentration in the trophoblast in late pregnancy. This rise was more marked and appeared earlier in placentae from patients with severe pre-eclampsia. Placentae from patients with pre-existing hypertension did not appear to differ from normal ones of similar periods of gestation. Acid phosphatase was localised in the trophoblast and decreased in amount in late pregnancy. This decrease was more marked, and occurred earlier in placentae from cases of severe pre-eclampsia and pre-existing hypertension than in normal placentae. Lactate dehydrogenase; malate dehydrogenase; di-phosphopyridine nucleotide diaphorase(D.P.N.D.); alpha-glycerophosphate dehydrogenase; and glucose - 6 - phosphate dehydrogenase were all present in the trophoblast throughout pregnancy without showing any apparent change in concentration. Succinate dehydrogenase could not be found in the trophoblast at any time, occurring only in the decidual cells of the placental bed. Leucine amino-peptidase showed a patchy distribution throughout the connective tissue stroma of the chorionic villi and within the walls of the larger blood vessels. It was concluded that the increasing concentration of alkaline phosphatase and glucose - 6 - phosphatase, and the decreasing concentration of acid phosphatase in the trophoblast are probably features of placental ageing, and may also be associated with placental insufficiency (Summary)