Neuropsychobiology 5: 317 321 (1979)
Lack of Counteracting Effect of Liposomes on Benserazide-Induced Hyperprolactinemia G. Murialdo, P. Masturzo, A. Polleri, A. Carolei and G. Toffano Institute of Internal Medicine, University of Genoa, Genoa; First Neurological Clinic o f the University of Rome, Rome, and Fidia Research Laboratories, Abano Termc
Key Words. Phospholipids • Liposomes • Aromatic amino acids decarboxylase inhibitors •
Prolactin
Introduction
Benserazide (Ro 4-4602), an inhibitor of aromatic amino acids decarboxylase, penetrates poorly the blood-brain barrier; in the rat, at doses lower than lOOmg/kg, it selectively pre vents decarboxylation in peripheral tissues, thus enhancing substrate uptake and monoamine concentration in the brain (Bartholini et al., 1967). Pontiroli et al. (1977) have shown that the administration of 50 mg of benserazide to humans increases serum prolactin levels. The finding is particularly interesting because it sug gests the possibility of studying the secretion of
prolactin and its regulation by altering selective ly monoamine concentrations in the involved structures, both inside and outside the bloodbrain barrier. Lloyd and Kaufman (1974) and Ráese et al. (1976) have found that phosphatidylserine in creases the biosynthesis of ¿-dopa and dopa mine by enhancing the affinity of tyrosine hydroxylase for its pteridine cofactor. In man, the administration of liposomes, made up with a mixture of brain cortex phospholipds contain ing phosphatidylserine as the active ingredient (Bruni et al., 1976a, b), induced a decrease of serum prolactin comparable to that obtainable with currently employed doses of hypoprolac-
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 5:10:14 PM
Abstract. Benserazide induces an increase of serum prolactin in man, possibly as the result of an impairment of the dopamine effect on the pituitary and/or on the outer median eminence caused by the inhibition on ¿-dopa decarboxylase. On the other hand, liposomes obtained from bovine brain cortex phospholipids reduce serum prolactin possibly through an effect of phosphatidylserine on dopamine biosynthesis at the level of tyrosine hydroxylase. Benserazide, given orally (125 mg) to 5 normal subjects, induced an increase of serum prolactin that did not change when 300 mg of phospholipid liposomes were given intravenously 60 min later. An increase of ¿-dopa synthesis does not seem to be capable to overcome the effects of the decarboxylase inhibition.
Murialdo/Masturzo/Polleri/Carolei/Toffano
318
Table I. Effect of benserazide and benserazide + BCPL administration on serum prolactin levels Case No.
Sex
Time, min -1 0
Benserazide 1 2 3 4 5 Mean SD Benserazide 1 2 3 4 5 Mean SD
125 mg orally F 9.0 F 12.5 F 23.0 M 6.2 M 15.0 13.14 6.44
-5
+ 30
8.3 11.8 15.0 5.7 11.5
10.2 27.0 67.0 22.0 48.0
10.46 3.56
34.84 22.58
+ 60
+ 90
+ 120
+ 150
+ 180
140.0 145.0 75.0 41.0 82.0
160.0 150.0 70.0 82.0 88.0
160.0 100.0 75.0 77.0 82.0
135.0 105.0 70.0 69.0 79.0
73.0 62.0 69.0 66.0 70.0
36.0 67.0 65.0 49.0 55.0
68.0 4.18
54.40 12.64
96.60 44.71
125 mg orally + BCPL 300 mg intravenously 5.0 110.0 115.0 F 6.0 25.0 150.0 F 15.0 13.0 48.0 F 5.0 2.1 38.0 M 4.2 4.5 34.0 4.5 M 93.0 12.3 10.5 60.0 8.56 4.77
6.96 4.58
47.50 40.33
110.20 41.73
120.0 170.0 50.0 34.0 98.0
88.00 47.73
94.40 54.77
98.80 35.60
67.0 145.0 55.0 32.0 86.0 77.00 42.76
91.60 28.28
48.0 150.0 52.0 32.0 74.0 71.20 46.50
53.0 130.0 52.0 30.0 70.0 67.00 37.97
+ 240
46.0 42.0 38.0 22.0 36.0 36.80 9.12
tinizing agents, such as ¿-dopa, bromocriptine, piribedil, acting via a dopaminergic pathway (Masturzo et al., 1977). With regard to these considerations, we wanted to investigate whether liposomes ob tained from bovine brain cortex phospholipids might affect benserazide-induced hyperprolac tinemia.
Materials and Methods 5 normal subjects, 2 men and 3 women, aged between 20 and 40 years, were studied. At the time of the experiment, the women were in the early phase of their normal ovarian cycle. All subjects were given orally 125 mg of benserazide at about 9 a.m. Prolactin was assayed 10 and 5 min before benserazide adminis
tration and 30, 60, 90, 120, 150, 180 and 240 min thereafter. 3 days later, the experiment was repeated and the subjects were given intravenously 300 mg of brain cortex phospholipid liposomes, 60 min after the administration of benserazide. This schedule was se lected in order to administer liposomes after the onset of the benserazide-induced hyperprolactinizing effect. Liposomes were prepared according to Bruni et al. (1976a, b) and contained phosphatidic acid (6.6%), phosphatidylcthanolamine (20.2%), phosphatidylserine (18.7%), lysophosphatidyl ethanolamine (15.0%), phosphatidylcholine (29.9%), sphingomyelin (9.4%), trace amounts o f fatty acids, amino acids, glycolipids. This preparation is hence referred to as BCPL. The effects o f liposomes alone were observed in 4 age-matched additional male subjects. Prolactin was assayed in sera by a double-antibody R1A method using a Biodata (Milan, Italy) kit. Refer ence preparation is hPRL NIH F ,. Method sensitivity is 0.8 ng/ml.
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 5:10:14 PM
Values are expressed in ng/ml o f serum ± SD. The time is indicated in relation to benserazide administration.
Lack of Liposomes Effect on Benscrazidc-Iiuluced Hyperprolactinemia
319
Fig. 1. Mean and SD of serum prolactin levels (PRL) after benserazide (125 mg orally; continu ous line) and after bcnserazide and subsequent administration of phospholipid liposomes (BCPL 300 mg intravenously; dashed line). The increase of serum prolac tin levels is significant in the two conditions with respet to basal values starting at 60 min (p
Lack of Counteracting Effect of Liposomes on Benserazide-Induced Hyperprolactinemia G. Murialdo, P. Masturzo, A. Polleri, A. Carolei and G. Toffano Institute of Internal Medicine, University of Genoa, Genoa; First Neurological Clinic o f the University of Rome, Rome, and Fidia Research Laboratories, Abano Termc
Key Words. Phospholipids • Liposomes • Aromatic amino acids decarboxylase inhibitors •
Prolactin
Introduction
Benserazide (Ro 4-4602), an inhibitor of aromatic amino acids decarboxylase, penetrates poorly the blood-brain barrier; in the rat, at doses lower than lOOmg/kg, it selectively pre vents decarboxylation in peripheral tissues, thus enhancing substrate uptake and monoamine concentration in the brain (Bartholini et al., 1967). Pontiroli et al. (1977) have shown that the administration of 50 mg of benserazide to humans increases serum prolactin levels. The finding is particularly interesting because it sug gests the possibility of studying the secretion of
prolactin and its regulation by altering selective ly monoamine concentrations in the involved structures, both inside and outside the bloodbrain barrier. Lloyd and Kaufman (1974) and Ráese et al. (1976) have found that phosphatidylserine in creases the biosynthesis of ¿-dopa and dopa mine by enhancing the affinity of tyrosine hydroxylase for its pteridine cofactor. In man, the administration of liposomes, made up with a mixture of brain cortex phospholipds contain ing phosphatidylserine as the active ingredient (Bruni et al., 1976a, b), induced a decrease of serum prolactin comparable to that obtainable with currently employed doses of hypoprolac-
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 5:10:14 PM
Abstract. Benserazide induces an increase of serum prolactin in man, possibly as the result of an impairment of the dopamine effect on the pituitary and/or on the outer median eminence caused by the inhibition on ¿-dopa decarboxylase. On the other hand, liposomes obtained from bovine brain cortex phospholipids reduce serum prolactin possibly through an effect of phosphatidylserine on dopamine biosynthesis at the level of tyrosine hydroxylase. Benserazide, given orally (125 mg) to 5 normal subjects, induced an increase of serum prolactin that did not change when 300 mg of phospholipid liposomes were given intravenously 60 min later. An increase of ¿-dopa synthesis does not seem to be capable to overcome the effects of the decarboxylase inhibition.
Murialdo/Masturzo/Polleri/Carolei/Toffano
318
Table I. Effect of benserazide and benserazide + BCPL administration on serum prolactin levels Case No.
Sex
Time, min -1 0
Benserazide 1 2 3 4 5 Mean SD Benserazide 1 2 3 4 5 Mean SD
125 mg orally F 9.0 F 12.5 F 23.0 M 6.2 M 15.0 13.14 6.44
-5
+ 30
8.3 11.8 15.0 5.7 11.5
10.2 27.0 67.0 22.0 48.0
10.46 3.56
34.84 22.58
+ 60
+ 90
+ 120
+ 150
+ 180
140.0 145.0 75.0 41.0 82.0
160.0 150.0 70.0 82.0 88.0
160.0 100.0 75.0 77.0 82.0
135.0 105.0 70.0 69.0 79.0
73.0 62.0 69.0 66.0 70.0
36.0 67.0 65.0 49.0 55.0
68.0 4.18
54.40 12.64
96.60 44.71
125 mg orally + BCPL 300 mg intravenously 5.0 110.0 115.0 F 6.0 25.0 150.0 F 15.0 13.0 48.0 F 5.0 2.1 38.0 M 4.2 4.5 34.0 4.5 M 93.0 12.3 10.5 60.0 8.56 4.77
6.96 4.58
47.50 40.33
110.20 41.73
120.0 170.0 50.0 34.0 98.0
88.00 47.73
94.40 54.77
98.80 35.60
67.0 145.0 55.0 32.0 86.0 77.00 42.76
91.60 28.28
48.0 150.0 52.0 32.0 74.0 71.20 46.50
53.0 130.0 52.0 30.0 70.0 67.00 37.97
+ 240
46.0 42.0 38.0 22.0 36.0 36.80 9.12
tinizing agents, such as ¿-dopa, bromocriptine, piribedil, acting via a dopaminergic pathway (Masturzo et al., 1977). With regard to these considerations, we wanted to investigate whether liposomes ob tained from bovine brain cortex phospholipids might affect benserazide-induced hyperprolac tinemia.
Materials and Methods 5 normal subjects, 2 men and 3 women, aged between 20 and 40 years, were studied. At the time of the experiment, the women were in the early phase of their normal ovarian cycle. All subjects were given orally 125 mg of benserazide at about 9 a.m. Prolactin was assayed 10 and 5 min before benserazide adminis
tration and 30, 60, 90, 120, 150, 180 and 240 min thereafter. 3 days later, the experiment was repeated and the subjects were given intravenously 300 mg of brain cortex phospholipid liposomes, 60 min after the administration of benserazide. This schedule was se lected in order to administer liposomes after the onset of the benserazide-induced hyperprolactinizing effect. Liposomes were prepared according to Bruni et al. (1976a, b) and contained phosphatidic acid (6.6%), phosphatidylcthanolamine (20.2%), phosphatidylserine (18.7%), lysophosphatidyl ethanolamine (15.0%), phosphatidylcholine (29.9%), sphingomyelin (9.4%), trace amounts o f fatty acids, amino acids, glycolipids. This preparation is hence referred to as BCPL. The effects o f liposomes alone were observed in 4 age-matched additional male subjects. Prolactin was assayed in sera by a double-antibody R1A method using a Biodata (Milan, Italy) kit. Refer ence preparation is hPRL NIH F ,. Method sensitivity is 0.8 ng/ml.
Downloaded by: King's College London 137.73.144.138 - 1/16/2019 5:10:14 PM
Values are expressed in ng/ml o f serum ± SD. The time is indicated in relation to benserazide administration.
Lack of Liposomes Effect on Benscrazidc-Iiuluced Hyperprolactinemia
319
Fig. 1. Mean and SD of serum prolactin levels (PRL) after benserazide (125 mg orally; continu ous line) and after bcnserazide and subsequent administration of phospholipid liposomes (BCPL 300 mg intravenously; dashed line). The increase of serum prolac tin levels is significant in the two conditions with respet to basal values starting at 60 min (p
