UGT1A1 polymorphisms associated with prolactin response in risperidone-treated children and adolescents with autism spectrum disorder.

The aim of this study was to investigate the association of drug-metabolizing enzyme and transporter (DMET) polymorphisms with the risperidone-induced prolactin response using an overlapping gene model between serum prolactin level and hyperprolactinemia in autism spectrum disorder (ASD) patients. Eighty-four ASD patients who were receiving risperidone for at least 1 month were recruited and then assigned to either the normal prolactin group or the hyperprolactinemia group based on their serum prolactin level. The genotype profile of 1936 (1931 single nucleotide polymorphisms (SNPs) and 5 copy number variation (CNVs) drug metabolism markers was obtained using the Affymetrix DMET Plus GeneChip microarray platform. Genotypes of SNPs used to test the accuracy of DMET genotype profiling were determined using TaqMan SNP Genotyping Assay kits. Eighty-four patients were selected for the allelic association study after microarray analyses (51 in the normal prolactin group, and 33 in the hyperprolactinemia group). An overlapping allelic association analysis of both analyses discovered five DMET SNPs with a suggestive association (P < 0.05) with risperidone-induced prolactin response. Three UGT1A1 SNPs (UGT1A1*80c.-364C > T, UGT1A1*93 c.-3156G > A, and UGT1A1 c.-2950A > G, showed a suggestive association with the risperidone-induced prolactin response and found to be in complete linkage disequilibrium (D' value of 1). In this DMET microarray platform, we found three UGT1A1 variants with suggestive evidences of association with the risperidone-induced prolactin response both measured by hyperprolactinemia and by prolactin level. However, due to the lack of validation studies confirmation and further exploration are needed in future pharmacogenomic studies.

Collagenolytic enzymes and progestin in induced ovulation in rabbits with hyperprolactinemia.

To clarify the possible role of collagenolytic enzymes and progestin in induced ovulation and to investigate whether progesterone interacts with these enzymes in leading to ovulation during the hyperprolactinemic state, the alterations of 2,4-dinitrophenyl-Pro-Gln-Gly-Ile- Ala Gly-Gln-D-Arg-OH peptidase (DNP-peptidase) and alpha-n-benzoyldl-Arg-beta-naphthylamide hydrolase (BANA-hydrolase) activities were measured in rabbit ovaries. The ovaries were primed with four daily sulpiride (SLP) injections followed by human chorionic gonadotropin (hCG) administration. The peripheral and ovarian progesterone, 20 alpha-hydroxypregn-4-en-3-one (20 alpha OHP) levels and ovulation rate at 14 hours after hCG administration in SLP-treated rabbits were significantly suppressed as compared with the control animals. The usual changes in DNP-peptidase and BANA-hydrolase activities in the follicular tissue at 8 and 10 hours after hCG were also altered by this abnormal hypersecretion of circulating prolactin. When progesterone was administered concomitantly with hCG to the hyperprolactinemic rabbits during ovulation induction, the ovulation rate was restored to a physiologic level comparable to that of the controls. These results suggest that both progesterone and collagenolytic enzymes are mandatory for follicular rupture induced by hCG and that progesterone may interact with these enzymes to facilitate the completion of the ovulatory process during the hyperprolactinemic state.

Hepatic and renal phosphomonoesterases and adenosine triphosphatases in chronic hyperprolactinaemic rats.

Influence of hyperprolactinaemia, induced endogenously by anterior pituitary transplantation on rat hepatic and renal cortical and medullary phosphomonoesterases and adenosine triphosphatases (ATPases) has been investigated. Although prolactin has a stimulatory effect on phosphomonoesterases and ATPases, it exhibits a specific and temporal influence on each subtype of hepatic and renal ATPases and phosphomonoesterases at different durations of pituitary transplantation. The specific activities of alkaline phosphatase and Na(+)-K+ dependent ATPases are activated in all the regions of different durations of experimentation. However, acid phosphatases, Ca2+ and Mg2+ dependent ATPases exhibit a differential response to prolactin in renal cortex, medulla and liver. Direct influence of prolactin on hepatic and renal phosphomonoesterases and ATPases is thus suggested.

[Role of enzymes of dopamine metabolism in the regulation of prolactin and thyrotropin secretion in hyperprolactinemia]. / Rol' fermentov obmena dofamina v reguliatsii sekretsii prolaktina i tireotropina pri sindrome giperprolaktinemii.

Altogether 24 women with the syndrome of hyperprolactinemia (SH), including 5 patients with significant PRL hypersecretion against a background of macro- and microprolactinemia, and 19 women with normoprolactinemic galactorrhea were investigated. The activity of dopamine-B-hydroxylase (DBH) and monoamino oxidase (MAO) (the key enzymes of dopamine metabolism) was determined by spectrophotometry. A different time course of secretion of PRL and TSH in metoclopramide testing was revealed in the patients with regard to the level of basal prolactinemia. The determination of MAO and DBH activity made it possible to estimate in more detail the state of dopaminergic control of PRL and TSH secretion in the syndrome of hyperprolactinemia.

Effect of cysteamine on the lysosomal enzymes of the hyperprolactinaemic rat pituitary.

The effect of cysteamine on the activity of lysosomal enzymes and the prolactin content of isolated hyperprolactinaemic cells has been investigated. In broken cell preparations, cysteamine markedly stimulated acid prolactin protease activity. In intact cells, however, cysteamine inhibited acid prolactin protease activity and beta-galactosidase. Moreover, the activities of alpha-mannosidase, acid phosphatase, beta-glucuronidase, total arylsulphatase and hexosaminidase were not changed by the addition of cysteamine. Cysteamine significantly depleted the cells of prolactin, and this action was not compromized by the inclusion of either leupeptin, chloroquine or NH4Cl in the incubation media. Taken together, these results indicate that cysteamine does not promote degradation of prolactin and hence depletion of prolactin from the pituitary through a mechanism involving lysosomal enzyme degradation.

GABAergic biochemical parameters of the tuberoinfundibular neurons following chronic hyperprolactinemia.

The effect of chronic hyperprolactinemia was studied on (a) GABA concentration in the pituitary anterior lobe; (b) GABA biosynthesis enzyme, glutamate decarboxylase (GAD) activity in the hypothalamic median eminence, and (c) GABA degradation enzyme GABA-transaminase (GABA-T) activity at both levels. In male rats bearing the prolactin-secreting tumor MtTF4 for 1 month or treated for 5 days with estradiol benzoate, the plasma prolactin concentration was markedly increased (between 4- and 10-fold basal values). In both cases, GABA concentration was significantly increased (40-60%) in the anterior pituitary lobe. A slight reduction (20-30%) in GABA-T activity was observed in the anterior lobe while no change in GAD or GABA-T activity was measured in the median eminence. These results are discussed in relationship to a possible feedback input of prolactin on the tuberoinfundibular GABAergic system.

Mass and in situ activity of tyrosine hydroxylase in the median eminence: effect of hyperprolactinemia.

The role of PRL in the control of catecholaminergic hypothalamic neurons of female rats was investigated. The in situ activity of tyrosine hydroxylase (TH) in neurites of these neurons was assayed by measuring the rate of accumulation of L-3,4-dihydroxyphenylalanine (DOPA) in the median eminence (ME) after the administration of a DOPA decarboxylase inhibitor. The mass of TH was measured by an immunoblot assay using rat TH as the standard. Hyperprolactinemia was induced by pituitaries implanted beneath a renal capsule. Hyperprolactinemia resulted in a significant increase in the in situ activity of TH without an increase in TH mass. The release of dopamine from hypothalamic neurons was assessed by measuring the concentration of dopamine in hypophysial portal plasma. The mean concentration of dopamine in portal plasma of rats bearing pituitary implants was 3 times that in controls. When circulating PRL was neutralized by administration of antiserum against rat PRL, the activity of TH was reduced significantly compared to that in animals treated with preimmune serum. In animals bearing pituitary implants, phosphorylation of TH in the ME was not different from that in control animals. We conclude that the biosynthetic and secretory activities of dopaminergic neurons of the hypothalamus are potentiated by PRL, but the potentiation is not due to an increase in the mass of TH or to the capacity of the neurites of the ME to phosphorylate TH.

Effects of hyperprolactinemia on FSH- or LH-induced activities of 17 beta-oxidoreductase, 5 alpha-reductase, and 17-hydroxylase in hypophysectomized rat testes.

Two pituitaries from 7-week-old female rats (Sprague-Dawley strain) were grafted under the capsule of the left kidney of a 49-day old male rat. The pituitary grafted and sham-operated rats were hypophysectomized at 56 days of age. The hypophysectomized rats were given daily injections of NIAMDD-oFSH-13 (20 micrograms/0.5 ml saline), NIAMDD-oLH-23 (9 micrograms/0.5 ml saline) or saline for 4 days starting from day 58. The treated rats and normal male rats were killed at 61 days of age. Testicular homogenates were incubated with [14C]4-androstene-3, 17-dione or [3H] progesterone, and enzyme activities per testes were estimated. Hypophysectomy caused significant decreases in activities of testicular 17 beta-oxidoreductase and 17-hydroxylase. The decreased activity of 17 beta-oxidoreductase was significantly stimulated by FSH or LH treatment, whereas the decreased 17-hydroxylase activity was stimulated only by LH treatment. Although pituitary grafts alone showed little or no effect on these enzyme activities in the hypophysectomized rats, the grafts significantly inhibited FSH-stimulated 17 beta-oxidoreductase activity and the LH-stimulated 17 beta-oxidoreductase and 17-hydroxylase activities but enhanced LH-induced 5 alpha-reductase activity. The present results confirm previous findings that an excess of prolactin directly inhibits LH-stimulated 17-hydroxylase activity but enhances LH-induced 5 alpha-reductase activity in the rat testis. The present results also demonstrate that the same grafts directly inhibit FSH-stimulated 17 beta-oxidoreductase activity but have no effect on FSH-induced 5 alpha-reductase activity.

Metoclopramide-induced hyperprolactinaemia: effects on corpus luteum function, endometrial steroid receptor concentrations and 17 beta-hydroxysteroid dehydrogenase activity.

Induced hyperprolactinaemia impairs ovarian follicular development, especially during the recruitment period. The consequences of hyperprolactinaemia during the luteal phase alone on corpus luteum function have not been characterized, nor have the actions of excessive circulating PRL on the endometrium. In this study, postovulatory 5-d administration of metoclopramide (MC) increased serum concentrations of PRL and decreased those of pregnenolone and progesterone indicating inhibition of steroidogenesis in the corpus luteum. This effect may partly explain the relatively common failure of implantation in association with induced ovulation using regimens leading to transient hyperprolactinaemia. In contrast to this, MC-induced hyperprolactinaemia during the mid-follicular (4 d) or early luteal phase of the cycle did not alter the concentrations of cytosol or nuclear oestrogen and progestin receptors or the activity of 17 beta-hydroxysteroid dehydrogenase in endometrial tissue. Thus, transiently elevated circulating PRL does not seem to have direct effects on female sex steroid receptors or their function in the proliferative or secretory endometrium.

Hyperprolactinemia enhances LH-stimulated 4-ene-5 alpha-reductase activity but inhibits LH-induced 17-hydroxylase activity in testes of hypophysectomized immature rats.

Two pituitaries from 7-week old female rats (Sprague-Dawley strain) were grafted under the capsule of the left kidney of 21-day old male rat. The pituitary grafted and sham-operated rats were hypophysectomized at 27 days of age. The hypophysectomized rats, in groups of 4, were given daily injections of 9 micrograms NIAMDD-oLH-23 (minimum effective dose) or saline for 3 days starting from day 29. Testicular homogenates were incubated with [3H]progesterone or [14C]4-androstene-3,17-dione, and enzyme activities per testes were estimated. Testicular HCG-binding sites were also measured. Hypophysectomy caused significant decreases in activities of testicular 5 alpha-reductase, 17-hydroxylase, and 17 beta-hydroxysteroid oxidoreductase. These decreased enzyme activities were significantly stimulated by LH treatment. Although pituitary grafts alone showed no effects on these enzyme activities in the testes of the hypophysectomized rats, the grafts significantly enhanced LH-stimulated 5 alpha-reductase activities but inhibited LH-stimulated 17-hydroxylase activity. Testicular LH/HCG receptors were significantly increased by the grafts, especially in the presence of LH, without affecting affinity for HCG. The present results demonstrate for the first time that hyperprolactinemia directly stimulates LH-stimulated 5 alpha-reductase activity in rat testes. The results also show that the same grafts directly inhibit LH-stimulated 17-hydroxylase activity, probably via postreceptor mechanisms.

Hyperprolactinemia and 5-alpha-reductase activity.

A number of experimental data indicate that hyperprolactinemia inhibits the activity of 5-alpha-reductase; however, no information is available about the time required for this enzyme to re-activate after prolactinemia has returned to normal values. In the present study, five normal caucasian men, whose fertility had previously been proven, were given HCG (5000 IU/day by intramuscular route for three days) both in basal conditions and after sulpiride-induced hyperprolactinemia (dosage = 200 mg/day for ten days). In both conditions, the plasma levels of prolactin (PRL), testosterone (T), dihydro-testosterone (DHT), 17-beta-estradiol (E2), and dehydroepiandrosterone sulfate (DHAS) were monitored during the treatment with HCG and for an additional 24 hrs after HCG discontinuation. All hormones were assayed by RIA. Our results demonstrate that hyperprolactinemia causes a marked decrease (58%) of DHT, a less marked decrease (39%) of T, an increase (43%) of DHAS whereas only a small increase (2%) of E2 was observed. Steroids were shown to behave differently after the HCG tests performed in the two experimental conditions. In particular, the levels of DHT had a much more pronounced increased after HCG in the second test than in the first; in contrast, both DHAS and E2 had a less marked response after the second test. Our data, on the one hand, confirm that 5-alpha-reductase is inhibited by hyperprolactinemia; on the other hand, the hyperprolactinemia-induced block of this enzyme appears to be rapidly reversible because the enzyme is reactivated within 48-72 hrs after normalization of prolactin levels. (Normal values of prolactin were on the average achieved on the 4th day after sulpiride discontinuation).(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin modulates peripheral androgen metabolism.

Although hyperprolactinemia may be associated with hyperandrogenism, if hirsutism develops, it is usually a mild form. This study was designed to investigate whether prolactin (PRL) modulates 5 alpha-reductase activity (5 alpha-RA), because 5 alpha-RA is known to be a major factor influencing the manifestation of androgenicity. Compared with normal women, euprolactinemic hirsute and both hyperprolactinemic hirsute and nonhirsute women had elevated levels of unbound testosterone (uT). Serum 3 alpha-androstanediol glucuronide (3 alpha-diol-G) was elevated only in patients who were hirsute, and serum 3 alpha-diol-G/uT ratios were elevated in euprolactinemic hirsute patients and normal in hyperprolactinemic hirsute patients. Genital skin 5 alpha-RA in vitro was elevated only in euprolactinemic hirsute women. The previously recognized positive correlation between 5 alpha-RA and the severity of hirsutism was dissociated with hyperprolactinemia. Human PRL incubated in vitro with normal genital skin also inhibited 5 alpha-RA. These data suggest that PRL modulates 5 alpha-RA and peripheral androgen metabolism and that other factors may also be involved in the evolution of hirsutism in hyperprolactinemia.