Studies on a rat-liver cell-sap protein yielding 3-[32P]-phosphohistidine after incubation with [32P]ATP and alkaline hydrolysis. Identification of the protein as ATP citrate lyase.

1. The rat-liver cell-sap material from which 3-[32P]phosphohistidine was previously isolated after incubation with [gamma-32P]ATP and alkaline hydrolysis, was shown to increase about 6-fold on a high-carbohydrate diet. This increase in 32P labelling corresponded to the increase in ATP citrate lyase activity of livers of rats fed on a high-carbohydrate diet, as reported by others. 2. ATP citrate lyase [ATP:citrate oxaloacetate-lyase (CoA-acetylating and ATP-dephopshorylating), EC 4.1.3.8] was purified from rat liver essentially according to the method of Plowman and Cleland (J. Biol. Chem., 242 (1967) 4239). The purified enzyme was incubated for a short time at 0 degree with [gamma-32P]ATP in the presence of 20 mM magnesium acetate. The phosphorylated protein was hydrolysed in alkali and the main part of the radioactivity was identified as 3-[32P]phosphohistidine. The identity of the phosphorylated amino acid was established by Dowex-1 chromatography, paper electrophoresis, paper chromatography and by analysis of the stability to acid. 3. It is concluded from these and previous results from this laboratory that ATP citrate lyase and nucleoside diphosphate kinase (ATP:nucleoside diphosphate phosphotransferase, EC 2.7.4.6) account for most of the normal rat-liver cell-sap protein which is rapidly phosphorylated by ATP.

Pregnancy-induced increase in metoprolol metabolism.

Five women who developed hypertension during pregnancy received metoprolol, 10 mg iv; 3 days later they received metoprolol, 100 mg by mouth. Blood and urine samples were collected after each dose. The same procedure was repeated 3 to 6 months after delivery. The apparent oral clearance of metoprolol during pregnancy exceeded that after pregnancy by a factor of 2 to 13. As a result, after oral dosing the peak plasma concentrations during pregnancy were only 12% to 55% those after delivery, and the plasma AUCs were reduced to the same extent. Oral bioavailability increased by a factor of 1.3 to 3.7 after pregnancy. Systemic clearance after pregnancy was 26% to 97% that during pregnancy, but this difference was not significant. Metoprolol plasma protein binding was the same on both study occasions. Our data cannot be explained by a change in gastrointestinal absorption, because the urinary recovery of metoprolol and its metabolites was slightly higher during pregnancy. It is concluded that the greater metoprolol clearance during pregnancy results from increased hepatic metabolism of the drug.

Plasma concentration-effect relationship of metoprolol during and after pregnancy.

The plasma drug concentration-effect relationship after an oral dose of 100 mg metoprolol has been studied in 8 women in the third trimester of a pregnancy complicated by hypertension. The study was repeated 3-5 months after parturition when all but 2 women were normotensive. Systolic and diastolic blood pressures (SBP and DBP) were measured in the sitting position followed by the change in heart rate on exercise. The average peak plasma concentration of metoprolol was almost 4-times higher in the non-pregnant state. Despite this difference, the reduction in exercise tachycardia and resting SBP was only slightly more pronounced after delivery than during pregnancy. In relation to the plasma drug concentration, metoprolol had four-times and twice the effect on heart rate and SBP during pregnancy as compared to the post partum period. The altered chronotropic response to metoprolol during pregnancy may be due to increased sensitivity or altered function of the beta-adrenergic system.

Increased oral clearance of metoprolol in pregnancy.

The disposition of oral metoprolol was studied in 5 women during the last trimester of pregnancy and 3 to 5 months after delivery. After a single oral dose of 100 mg the individual peak plasma concentration in the pregnant state was only 20-40% of that after pregnancy. The plasma half-lives of metoprolol were about the same during (average 1.3 h) and after pregnancy (average 1.7 h). By contrast, the area under the plasma concentration versus time curve was much smaller during (mean 262 nmol/1 X h) than after (mean 1298 nmol/1 X h) pregnancy, resulting in an average apparent oral clearance (Clo) of metoprolol that was 4.4 times higher during (362 ml X kg-1 body-weight X min-1) than after pregnancy. The increased Clo in pregnancy is assumed to be due to enhanced hepatic metabolism of the drug. The possible clinical consequence of the difference in the disposition of metoprolol is discussed.

The incidence of hypertensive disease in pregnancy.

Incidence figures for hypertensive disease in pregnancy (HDP) vary widely in epidemiological studies due to variations in definitions, the occurrence of risk factors and differing methods of data collection. In Uppsala county all pregnant women with a diastolic blood pressure of 90 mmHg or more were prospectively registered within a 2-year-period. The incidence of hypertension noted in the antenatal clinics was found to be 7.2%. In 56% of the cases hypertension was first noted after 37 weeks of gestation. The group of patients presenting before term with hypertension not normalized by bed rest in hospital and without complicating factors was only 14% of the whole material. The implications of the findings for discussions on therapy and complications in HDP are discussed.

Methodological problems in studies on hypertension therapy during pregnancy.

As yet, no distinct aetiological factor underlying hypertension in pregnancy has been disclosed, and there is therefore no clearcut treatment for this condition. The lack of well-defined end-points makes it difficult to plan and evaluate the results of studies on the treatment of hypertension during pregnancy. However, we cannot await the solution to the puzzle of pre-eclampsia before providing treatment for this hypertension. Well-designed investigations to determine the most effective form of such treatment are therefore of great value and must be carried out in spite of the many problems associated with these studies. If given due consideration, as discussed in this paper, this problem can be alleviated.

Oral contraceptive tablets containing 20 and 30 micrograms of ethinyl estradiol with 150 micrograms desogestrel. Their influence on lipids, lipoproteins, sex hormone binding globulin and testosterone.

The effect of two oral contraceptive (OC) pills, both containing 150 micrograms of desogestrel, but with 20 (Mercilon) or 30 micrograms (Marvelon/Desolett) of ethinyl estradiol on plasma levels of lipids, lipoproteins and sex hormone binding globulin (SHBG), total and free testosterone were compared in a double-blind, randomized, two-center study in a total of 60 women over one year. A significant rise with Marvelon but not with Mercilon was seen in total cholesterol, HDL cholesterol, HDL-3 and apolipoprotein B, whereas LDL cholesterol decreased with Mercilon only. These effects resulted in significant differences between the two groups in the magnitude of responses in all these parameters except HDL-3. HDL-2, apolipoprotein A-1 and total phospholipids were elevated with both pills after treatment and with no difference in the degree of response between groups. The HDL/LDL cholesterol ratio tended to increase in both groups and that of apolipoproteins A-1/B in the women on Mercilon. Total triglycerides increased in both groups, but more in the women on Marvelon. Total testosterone decreased, particularly in the Marvelon group, whereas the two pills caused a similar increase in SHBG and decrease in free testosterone. It is concluded that the direction of changes in plasma lipids and lipoproteins with both these pills may as a whole be interpreted as beneficial, and that the differences in effect on LDL cholesterol and apolipoprotein B may suggest a slightly advantageous effect of Mercilon in this aspect. However, the clinical significance of these changes is uncertain. The results indicate a lack of androgenicity of both pills.

PIP: In Sweden, physicians followed women aged 18-40 for more than 12 months to determine the effects of two oral contraceptives (OCs) on plasma lipids, lipoproteins, sex hormone binding globulin (SHBG), and total and free testosterone. This double-blind comparative study examined OCs with 150 mcg desogestrel and 20 mcg ethinyl estradiol (Mercilon) and with 150 mcg desogestrel and 30 mcg ethinyl estradiol (Marvelon). The women served as their own controls. The Marvelon group experienced significant increases in total cholesterol (p 0.01 at 6 months and p 0.05 at 12 months), high density lipoprotein (HDL) cholesterol (p 0.01 at 6 months), HDL-3 (p 0.01 at 6 months), and apolipoprotein B (p 0.001 at 6 months and p 0.05 at 12 months), but the Mercilon group did not. Low density lipoprotein (LDL) cholesterol fell substantially only in the Mercilon group (p 0.05 at 6 months). HDL-2, apolipoprotein A-1, and total phospholipids increased significantly with both OCs. The degree of response did not differ between the two groups, however. At 6 months, the HDL/LDL cholesterol ratio was significantly higher in both groups than it was before treatment (p 0.01 for Mercilon and p 0.05 for Marvelon). The apolipoproteins A-1/B ratio increased significantly only in the Mercilon group (p 0.01 at 12 months). After treatment, total triglycerides increased significantly in both groups, especially in the Marvelon group (p 0.001 for both 6 and 12 months; p 0.05 for Mercilon group). Total testosterone decreased significantly in both groups, especially in the Marvelon group (p 0.001 vs. p 0.01). The OCs had similar significant effects on SHBG (increase) and on free testosterone (decrease). These findings indicate that both OCs have a beneficial effect on lipid and lipoprotein profiles with Mercilon having a somewhat greater beneficial effect on LDL cholesterol and apolipoprotein B than Marvelon. The OCs have an anti-androgenic effect.

The rhesus monkey as a model for studies of pregnancy induced changes in metoprolol metabolism.

Five pregnant Rhesus monkeys were catheterized in the hepatic and femoral veins. They were simultaneously given 168 or 176 micrograms of 3H-metoprolol intravenously, and 9 mg of metoprolol per kg body weight orally. The same procedure was repeated a few months after delivery. Analyses of the unlabelled drug in blood were made by gas-chromatography and of the 3H-labelled metoprolol, by liquid scintillation. The apparent volume of distribution as well as the terminal half-lives of metoprolol were in the same range during pregnancy and in non-pregnancy. The oral bioavailability of metoprolol was lower (6-22%) during pregnancy than in non-pregnancy (9-49%). The apparent oral clearance and the intrinsic hepatic clearance were in a similar range although there was a greater variation in the intrinsic clearance values. The former clearance estimate was lower in the non-pregnant state only for three of the five animals. The systemic clearance varied very little and was in the same range during pregnancy and in non-pregnancy. The changes in apparent oral clearance and in oral bioavailability of metoprolol between the pregnant and non-pregnant Rhesus monkey are similar to the changes observed in pregnant women, although the absolute values are different.

Comparison of different clearance estimates for metoprolol in the rhesus monkey.

After oral administration, the fraction of unchanged drug available systemically is predominantly governed by hepatic drug-metabolizing enzyme activity and/or binding to the liver. If the "well stirred" model for hepatic elimination mimics reality, the apparent oral clearance (Clo) of metoprolol, a drug which is completely absorbed and metabolized only by the liver, should reflect the intrinsic clearance (Cli), i.e., the maximum enzyme activity in absence of blood flow limitations. According to theory, the hepatic venous (hv) drug concentrations after an i.v. dose are also a function of Cli. This postulate has previously been verified in the isolated perfused rat liver by others and has now been tested by us in the intact rhesus monkey. We have compared Clo, Cli and the systemic clearance (Cls) of metoprolol in six rhesus monkeys catheterized in the hepatic and femoral veins (hv; fv). They were given simultaneously 37 to 73 micrograms of [3H]metoprolol i.v. and 9 mg of metoprolol per kg b.w. orally. Unlabeled drug was analyzed in plasma by gas chromatography and 3H-labeled metoprolol by liquid scintillation after liquid chromatography separation. The Cls [dose i.v./area under the blood concentration vs. time curve in the femoral vein (AUCs)] varied between 27 and 32 ml X kg-1 X min-1. As expected, the Clo (doseo/AUCs) was considerably higher and ranged from 89 to 147 ml X kg-1 X min-1. The Cli (dosei.v./AUChv) was in the same range as Clo (46-163 ml X kg-1 X min-1). The determined oral availability was 19 to 31% with a mean of 25.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective controlled trial of metoprolol-hydralazine treatment in hypertension during pregnancy.

In an open, controlled trial, treatment with a combination of metoprolol and hydralazine was compared with non-pharmacological management of mild and moderate hypertension in pregnancy. One hundred and sixty-one women participated in the study. The drug-treated group showed significantly better blood pressure control than the group not given antihypertensives. Induction of labor before term, because of maternal or fetal complications, was somewhat more frequent in the control group. Nine women in the treatment group and 5 in the control group developed albuminuria. Three infants in the drug-treated group died perinatally, and one in the control group. The outcome for the newborns was similar in both groups concerning birth weight, head circumference and Apgar score and in the frequencies of respiratory distress, bradycardia and hypoglycemia. The better blood pressure control achieved with these drugs makes it possible to treat the patient at home and reduce the risk of emergency delivery, but treatment does not seem to be mandatory for a good outcome of the pregnancy in cases of mild and moderate hypertension during pregnancy.