Paul C. MacDonald

The phosphohydrolase activity in lamellar bodies and its relationship to phosphatidylglycerol and lung surfactant formation

Phosphohydrolase activity of a lamellar body-enriched preparation from pig lung was examined to ascertain if two separate enzymes catalyze the hydrolysis of phosphatidic acid and phosphatidylglycerol 3-phosphate. From sulfhydryl inhibition, heat inactivation and substrate specificity studies, we suggest that one phosphohydrolase may account for the hydrolysis of both substrates. The relationship of the reported experiments to the biosynthesis of the glycerophospholipids present in surfactant is discussed.

Isolation and Characterization of 5α-Pregnane-3, 20-dione and Progesterone in Peripheral Blood of Pregnant Women

5Α-Pregnane-3,20-dione and progesterone were isolated from a pregnancy plasma pool and were identified by using a combination of chromatographic techniques and mass spectrometry. Antibodies to progesterone were obtained in rabbits by immunization with progesterone-1Α-carboxyethyl-thioether-thyroglobulin. The raised antibodies were of high affinity and one of them cross-reacted (137%) with 5Α-pregnane-3,20-dione. This property was used to develop radioimmunoassays for measuring circulating levels of both progesterone and 5Α-pregnane-3,20-dione in pregnancy plasma. The levels of both progesterone and 5Α-pregnane-3,20-dione increase throughout pregnancy, but a highly significant increase is observed only after the 32nd week of gestation.

Origin of Estrogen and Regulation of Its Formation in Postmenopausal Women

In premenopausal, ovulatory women, estrogen arises by two mechanisms. It is believed that the biologically more important of these is the synthesis of 17β-estradiol in the developing follicle. This obtains since 17β-estradiol is a more potent estrogen than that produced by the second mechanism, i.e., the extraglandular formation of estrone from circulating andro-stenedione. The rate of extraglandular estrone formation does not vary appreciably during the ovarian cycle (Fig. l-l).1 On average, about 3 mg of androstenedione are produced each day in young women and 1.5% of plasma androstenedione is aromatized (the process of converting androgen to estrogen) to estrone in extraglandular tissues.1–4 Thus, approximately 45 μg of estrone arise by this mechanism. At the extremes of the ovarian cycle, this amount of estrone may constitute 50% or more of the total estrogen produced in young women.1 The rate of secretion of 17β-estradiol by the ovary, however, varies widely during the ovarian cycle (Fig. 1-1). It is estimated that the rate of secretion of 17β-estradiol varies from 20–40 μg/day early and late in the cycle to as much as 600–1000 μg/dayjust prior to the midcycle LH (luteinizing hormone) surge and ovulation.1