1. Electrolyte transport characteristics were examined in erythrocytes from 13 normal men and from two groups of women: (i) taking combined oral contraceptive preparations (O/C, n = 10), and (ii) ovulatory women (non-O/C, n = 10) pre- and post-ovulation, at the same time intervals (days 7–10 and days 15–18) during a menstrual cycle. 2. With rubidium ( 86 Rb + ) used as a potassium analogue, co-transport (ouabain-resistant, fruse-mide-sensitive 86 Rb + influx) values were found to be lowest in non-O/C women (28 ± se 2.5 nmol h −1 10 −9 cells) and highest in men (56 ± 5.7, P < 0.001), with results between the two in women taking O/C (42 ± 4.2, P < 0.05 vs men, P < 0.01 vs non-O/C). Passive 86 Rb leak (frusemideand ouabain-resistant) was significantly lower in men (13 ± 1.6 nmol h −1 10 −9 cells) than in both groups of women (non-O/C 29 ± 1.8, P < 0.001; O/C 25 ± 1.2, P < 0.001). There was no cyclical variation within either group of women. 3. Maximum ouabain binding (number of Na + ,K + -ATPase units) was the same in all groups. Na + ,K + -ATPase activity, as determined by ouabain-sensitive 86 Rb influx, was the same in men and non-O/C groups, but was significantly suppressed in O/C compared with both men ( P < 0.01) and non-O/C women ( P < 0.05). 4. The differences found were not due to alterations in either progesterone or aldosterone, but could represent an androgenic effect in vivo of the 19-nortestosterone derivatives in combined oral contraceptive preparations.

1. Urine free dopamine was estimated at predetermined points of the menstrual cycle in normal volunteer subjects and in women taking a combined oral contraceptive. 2. There was no alteration in 24 h urine dopamine during the normal menstrual cycle but, in contrast, combined oral contraceptives produced a fall which recovered premenstrually. 3. In 19 primigravid subjects 24 h urine free dopamine was estimated at monthly intervals throughout pregnancy and at the time of the postnatal examination. 4. Urine dopamine was elevated throughout pregnancy when compared with postnatal values. Women receiving an oral progestogen contraceptive at the time of the postnatal examination showed a further fall in urine dopamine.

1. Erythrocyte carbonic anhydrase I was measured by immunoelectrophoresis in blood samples taken at intervals during the menstrual cycle of 26 normal women. Plasma progesterone concentrations were also measured in 18 of these subjects. In every case, the erythrocyte carbonic anhydrase I concentration reached a maximum at that point in the cycle when there was maximum secretion of progesterone. Statistical analysis indicated that the observed changes in erythrocyte carbonic anhydrase I concentration are highly significant and that erythrocyte carbonic anhydrase I and plasma progesterone concentrations are significantly correlated. 2. In three pregnant subjects the erythrocyte carbonic anhydrase I concentration showed a steady increase up to term. 3. Women taking progestogens in contraceptive pills, in doses of 1 mg/day or greater, had significantly higher concentrations of erythrocyte carbonic anhydrase I compared with females receiving no medication. 4. These observations strongly suggest that there may be a causal connection between plasma progesterone concentration and erythrocyte carbonic anhydrase I concentration in women.

1. The results of ambulatory blood pressure control in nineteen patients who were hypertensive on oral contraceptives are presented. 2. Withdrawal of the oral contraception in this group of patients reduced the average blood pressure significantly. Seven of the patients became normotensive after stopping the medication. 3. Hypertension was found among the relatives of the patients in twelve cases.

1. There are conflicting reports regarding the effect of oral contraceptives on serum and erythrocyte folate concentrations and on folate absorption. A detailed study of this problem was therefore undertaken. 2. It was first ascertained that there was no significant variation in serum folate concentrations at different stages in the normal menstrual cycle. 3. No significant difference was found in fasting serum folate concentrations between control subjects and those taking oral contraceptives. 4. Synthetic sex hormones did not inhibit jejunal pteroylpolyglutamate hydrolase in vitro. 5. Tests of absorption of pteroylglutamic acid (folic acid) and pteroylpolyglutamates in controls and women taking oral contraceptives showed no difference between the two groups, provided the subjects were presaturated with pteroylglutamic acid. Without presaturation, the rise in serum folate after oral pteroylpolyglutamates was significantly decreased in the women taking oral contraceptives, suggesting that the latter may alter folate clearance from the blood.

1. A vitamin B 6 -deficient diet was fed to an adult male subject to confirm previously described changes in tryptophan metabolism and urinary 4-pyridoxic acid excretion, and erythrocyte alanine and aspartate aminotransferase activities. 2. The results were compared with those obtained in women taking oestrogen-containing oral contraceptives. 3. The development of dietary vitamin B 6 deficiency was indicated by decreased 4-pyridoxic acid excretion, increased urinary concentrations of xanthurenic acid, kynurenine and 3-hydroxykynurenine, an elevated 3-hydroxykynurenine/3-hydroxyanthranilic acid ratio and impaired erythrocyte aminotransferase activities. 4. Tryptophan metabolites and 4-pyridoxic acid excretion were determined in thirty-one women when they had been taking an oral contraceptive for 6–36 months. Of these, twenty-six had abnormal tryptophan metabolism, but the 4-pyridoxic acid was decreased in only seven. In six of these seven a raised 3-hydroxykynurenine/3-hydroxyanthranilic acid ratio supported a diagnosis of subclinical vitamin B 6 deficiency; erythrocyte alanine aminotransferase activity was determined in five of the six, and was decreased in three. 5. Erythrocyte aminotransferases were determined in sixteen women when they had been taking an oral contraceptive for 3–6 months, and in thirty-four women after 6–36 months treatment. Neither group showed any change in alanine aminotransferase activity, but the aspartate aminotransferase was elevated in the group treated for 6 months or longer.