Variation in Activity of Monoamine Metabolizing Enzymes in Rat Liver During Pregnancy

Abstract

I Catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) activities in rat liver were measured during pregnancy, parturition and postpartum. Compared with activity in non-pregnant controls, both enzymes showed a significant decrease in activity which was most pronounced at day 18.2 The metabolism of intravenously infused [3 HI -adrenaline to [3HI -metanephrine and to [3 HI -acidic metabolites was also significantly depressed during pregnancy but had returned to control values by the 21 st day. 3 The effects of reserpine and/or nialamide on hepatic COMT and MAO were studied in control and 20-day-pregnant rats. Their action on COMT activity differed in the two groups. MAO was inhibited to a similar extent in these groups whether the drugs were given separately or in combination. 4 It seems possible that the changes in endocrine function which occur during pregnancy are responsible for the observed alterations in enzyme activity.

EFFECTS OF THYROIDECTOMY AND l‐THYROXINE ON ADRENALINE AND NORADRENALINE CONCENTRATIONS IN THE ADRENAL GLANDS AND PLASMA OF RATS DURING THE PRO‐OESTROUS PHASE OF THE OESTROUS CYCLE AND PREGNANCY

“…Considering evolutionary changes in the ratio of free and bound corticosteroids, oestrogens and progesterone, one can easily suggest that thyroid function which is more or less dependent on the normal function of the above hormones is certainly affected by the fluctuations which take place in these hormones during pregnancy (Wiest, Kidwell & Balough, 1968;Lau, Liao & Petropoulos, 1971;Shaikh, 1971). All these hormones have been shown to have a direct effect on the enzymes of monoamine metabolism (Phorecky & Wurtman, 1971;Parvez & Parvez, 1973;Holzbauer & Youdim, 1973;Parvez et al, 1975;. Therefore any consequent change in corticosteroids, oestrogens or progesterone possibly induced by thyroid deficiency should directly affect the plasma level of adrenaline in pregnant rats.…”

“…Most of these studies have been confined to normal animals and little attention has been given to the effect of hormones on monoamine regulation during hormonal deficiencies. Recently, evidence has been provided that the effects of drugs and hormones on monoamine metabolism are greatly modified during various physiological states such as pregnancy and the oestrous cycle (Parvez, Parvez & Youdim, 1975;Parvez, Parvez, Raza-Bukhari & Youdim, 1976). The present experiments were performed to study the influence of thyroidectomy during pregnancy and in pro-oestrus upon the storage and release of adrenaline and noradrenaline from adrenal gland into plasma.…”

DECREASED PHENYLETHANOLAMINE‐N‐METHYLTRANSFERASE AND CATECHOL‐O‐METHYLTRANSFERASE ACTIVITY IN RABBIT ADRENAL GLANDS DURING PREGNANCY

“…A similar explanation may conceivably be applied to the lowered COMT activity which is also a methyltransferase enzyme. An analysis of in vivo and in vitro effects of sex steroid hormones on monoamine catabolism ha's been made recently by Youdim, Holzbauer & Woods (1974) and others (Parvez et al, 1975) in non-pregnant and pregnant rats. Oestrogens and progesterone alter COMT activity (Wurtman & Axelrod, 1966;Parvez et al, 1975).…”

“…An analysis of in vivo and in vitro effects of sex steroid hormones on monoamine catabolism ha's been made recently by Youdim, Holzbauer & Woods (1974) and others (Parvez et al, 1975) in non-pregnant and pregnant rats. Oestrogens and progesterone alter COMT activity (Wurtman & Axelrod, 1966;Parvez et al, 1975). Blood concentrations of oestrogens and progesterone change considerably during late pregnancy (Shaikh, 1971;Weist, 1970) and both hormones have been shown to exert an important influence on monoamine catabolism (Holzbauer & Youdim, 1973;Southgate, 1972) with progesterone acting as a stimulator and oestrogens as inhibitors.…”

“…Animal experiments provide evidence that the monoamine content of peripheral and central nervous systems is altered during pregnancy (Kopin & Wurtman, 1963;Sjoberg, 1968). The binding, uptake and metabolism of radioactively labelled amines by the tissues of pregnant animals differ from those of non-pregnant female animals (Wurtman, Axelrod & Potter, 1964;Parvez, Parvez & Youdim, 1975). Our previous studies have shown that the processes of monoamine regulation have an important link with the termination of pregnancy (Parvez, Gripois & Parvez, 1973a;Parvez, Parvez & Gripois, 1973b) in the rabbit, whilst pregnant women have a significantly elevated neurotransmitter monoamine content in the blood close to onset of labour (Zuspan, 1970;Zuspan & Zuspan, 1973).…”