The placental alkaline phosphatase variant D and natural selection. Relationship to complications of pregnancy and to "the Regan isoenzyme".

Abstract

The placental alkaline phosphatase variant D is controlled by a gene which in most populations is rare (0.001–0.007). A significant increase of abortions in previous pregnancies was found in a series of deliveries from Sweden where the placenta (fetus) showed the D-variant. Among deliveries after various complications during pregnancy the D-variant was found in an increased frequency compared to a series of unselected, consecutive deliveries. In 1973 Inglis et al. claimed that the D-variant occurs in a frequency of 40–50% among cancer patients displaying ectopic (derepressed) heat-stable alkaline phosphatase (“the Regan isozyme”). A reexamination of their data suggests that the D-variant is not associated with cancer and that the identity between “the Regan isozyme” and placental alkaline phosphatase is still an open question.