Plasma cholesterol in pregnancy rhesus monkeys

Pregnancy-associated esterase in sera of baboons

Baboon serum samples were resolved by starch gel electrophoresis and polyacrylamide gradient gel electrophoresis and stained with naphthol substrates for esterase activity. An esterase that hydrolyzed alpha-naphthyl butyrate in preference to alpha-naphthyl acetate was found in very high activities in some individuals but not others. It migrated just cathodal of the albumin band in starch gels. In polyacrylamide gradient gels, it co-migrated with albumin and had an apparent molecular weight of approximately 65,000 daltons. Electrophoretic analysis by gel electrophoresis of random serum samples from male and female baboons indicated that this esterase was present only in the sera of pregnant baboons. Further investigation of serial samples collected from carefully monitored baboons confirmed that the amount of activity of this esterase was correlated with stage of pregnancy. Therefore, it was named pregnancy esterase (PE). PE was detectable by gel electrophoresis and chromogenic staining techniques as early as day 30 of pregnancy; its activity gradually increased with progressive pregnancy and reached maximum activity near full term (182 days). Soon after parturition, the activity of PE decreased rapidly and was not detected in maternal sera by day 14 postpartum. No evidence of PE was detected in sera of pregnant humans.

Vitamin C status, serum cholesterol levels and bile composition in the pregnant guinea-pig

1. Pregnant guinea-pigs receiving a low dose of L-ascorbic acid (0.2 mg/100 g body-weight per d) developed a hypercholesterolaemia in the third trimester of pregnancy, whereas no change in serum cholesterol levels was observed in pregnant animals receiving a higher dose of the vitamin (2 mg/100 g body-weight per d). 2. Pregnancy in the group of guinea-pigs receiving the higher dose of L-ascorbic acid was associated with an increased biliary secretion of bile acids. No change was observed in the biliary secretion of bile acids in pregnant animals receiving the lower dose of L-ascorbic acid, but these animals secreted significantly more cholesterol. 3. Changes in the biliary secretion of cholesterol and bile acids in the pregnant guinea-pig according to L-ascorbic acid intake were reflected in the composition of the gall-bladder bile. Thus, the gall-bladder bile of guinea-pigs receiving the lower dose of L-ascorbic acid contained more cholesterol, while the gall-bladder bile of those animals receiving the higher dose of the vitamin had a higher content of bile acids. 4. The increased cholesterol content of the gall-bladder of pregnant guinea-pigs receiving the lower dose of L-ascorbic acid resulted in decreased bile acid:cholesterol and phospholipid:cholesterol values, conditions predisposing to cholelithiasis.

Cholesterol metabolism and placental transfer in the pregnant Rhesus monkey

The placental transfer of cholesterol (5-cholesten-3beta-ol) was investigated by giving pregnant rhesus monkeys cholesterol-1alpha-(3)H or cholesterol-4-(14)C and then determining the cholesterol specific activity (SA) in maternal serum and in fetal serum and tissues. An isotopic steady state was established in five pregnant animals by the daily feeding of a tracer dose of cholesterol-4-(14)C. Comparison of maternal and fetal serum cholesterol SA revealed that an average of 42.6% of the serum cholesterol in the term fetus originated by transfer from the maternal blood. The remainder presumably arose by fetal synthesis de novo. Fetal tissues had cholesterol SA equal to or slightly less than that of fetal serum, except for brain which had a SA only 5% that of fetal serum. In other studies a single intravenous dose of radioactive cholesterol was given to either mother or fetus in late pregnancy. The time for detectable passage across the placenta in either direction was between 4 and 24 hr. With maternal administration of the isotope, there was equilibration of maternal and fetal serum cholesterol SA after 10-12 days. With fetal injection of isotopic cholesterol, however, the maternal cholesterol SA never attained a level more than 5% of fetal SA. This indicated that the net cholesterol flux was strongly in the direction of mother to fetus. Serum cholesterol levels were significantly greater in maternal than in fetal serum (80.3+/-18.5 vs. 59.6+/-15.6 mg/100 ml). Maternal serum cholesterol concentration in the monkey was significantly lower in late pregnancy than during the puerperium. Studies of breast milk indicated that approximately two-thirds of milk cholesterol was transferred from the maternal blood.