Prolactin size variants during pregnancy in women with ovulatory hyperprolactinemia: characterization by isoelectric focusing and lectin affinity chromatography.

Previous studies from this laboratory have demonstrated the occurrence of important changes in PRL size heterogeneity in women with ovulatory hyperprolactinemia during gestation. A similar observation has been made, in normal women, for glycosylated PRL, which shows a progressive decrease as pregnancy progresses. In this study we decided to investigate the contribution of G-PRL on PRL heterogeneity throughout gestation in women with ovulatory hyperprolactinemia. Serum samples obtained throughout gestation were analysed by SDS-PAGE followed by immunoblotting and by isoelectric focusing of gels as well. The results indicated that, independent of the stage of pregnancy, the relative amounts of G-PRL as compared with the nonglycosylated form of the hormone remained quite constant. In addition, isoelectric focusing analyses of serum samples consistently resulted in an identical isoelectric point of PRL throughout all of the gestational period. These results suggested that changes in the relative proportions of PRL size species during pregnancy were not correlated with the degree of PRL glycosylation. Moreover, these observations further extended and supported the concept that the occurrence of PRL size heterogeneity depends mainly on thiol-disulfide interchange mechanisms, among PRL molecules, at the pituitary level.

Reduced dopaminergic inhibition of thyrotropin release in hyperprolactinemic ovulatory women.

It has been suggested that menstrual irregularities in hyperprolactinemia are secondary to an increase in hypothalamic dopaminergic activity via a short loop positive feedback of prolactin (PRL). We have studied this question in a relatively new syndrome characterized by hyperprolactinemia without derangements of the hypothalamic-pituitary-ovarian function due to macroprolactinemia (abnormal high amounts of big-big PRL). Central dopaminergic activity was investigated by the administration of the dopamine antagonist domperidone to normal women (n = 7) and women with anovulatory (n = 6) and ovulatory hyperprolactinemia (n = 2). The effects of domperidone were evaluated in all subjects by the measurements of radioimmunoassayable circulating serum PRL and TSH levels. All subjects had a significant increase in serum PRL levels after 90 min of domperidone administration. Anovulatory hyperprolactinemic subjects showed the highest response to domperidone in terms of TSH, whereas normal women and women with ovulatory hyperprolactinemia had similar increments in TSH serum levels after the administration of the dopamine antagonist. These results support the observation that an increase of hypothalamic dopaminergic activity in hyperprolactinemia may account in part for the presence of menstrual irregularities. The presence of a similar pituitary responsiveness in terms of TSH to domperidone in normal and ovulatory hyperprolactinemic women suggests a similar hypothalamic dopaminergic activity in both group of subjects. These findings might offer an explanation for the coexistence of normal ovulatory cycles in spite of hyperprolactinemia.

[Prolactin variants in serum and amniotic fluid of women with ovulatory hyperprolactinemia]. / Variantes de prolactina en suero y líquido amniótico de mujeres con hiperprolactinemia ovulatoria.

There is enough evidence that prolactin (PRL), like many other pituitary hormones, is composed by multiple forms that differ from each other by size charge. Although they can be seen in the pituitary glands of a variety of species, their biological significance, identity and chemical nature still remain poorly understood. Recently, a new syndrome characterized by normal ovarian function in the presence of sustained hyperprolactinemia has been reported by our group. In these women, highly abnormal percentages of serum big big PRL have been consistently demonstrated. This observation suggests that big big PRL is immunologically similar, but biologically less active than monomeric or little PRL. In this study we have determined then molecular size heterogeneity of immunoreactive PRL in serum and amniotic fluid from two ovulatory hyperprolactinemic subjects (subjects A and B) who had, under non-pregnant conditions, large amounts of serum big big PRL, throughout different stages of parturition. Control subjects consisted of two women at the end of pregnancy in whom PRL species demonstrated a normal size distribution (subjects C and D). Mean basal levels of PRL were the highest in subjects A and B and remained constant during labor. In the control subjects a remarkable decline in PRL levels was observed during the periparturitional period. This pattern of PRL release was not correlated with changes in steroid hormone concentrations. The relative proportions of PRL size variants throughout delivery showed no apparent changes in all four subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of serum prolactin throughout the menstrual cycle and pregnancy in hyperprolactinemic women with normal ovarian function.

We have demonstrated the selective secretion of high mol wt PRL series (big big PRL) in women with hyperprolactinemia and normal ovarian function. This observation suggests that big big PRL is immunologically similar, but biologically less active, than monomeric or little PRL. In this study we determined the molecular size heterogeneity of immunoreactive PRL in the serum from two ovulatory hyperprolactinemic women (subjects A and B) who had large amounts of serum big big PRL during a menstrual cycle and/or gestation. Serum samples obtained throughout the menstrual cycle (days 6, 10, 14, 17, 23, and 28, taking as day 1 the first day of bleeding) and pregnancy (weeks 7, 9, 11, 15, 20, 25, 30, 34, and 38) were fractionated by gel filtration chromatography. PRL was identified in column eluates by specific RIA. Two additional pregnant women, one with a bromocriptine-treated PRL-secreting adenoma (subject C), and a normal woman (subject D) were studied. Big big PRL was the predominant species throughout the different phases of the menstrual cycle in subject B, comprising 70-80% of the total immunoreactive PRL. Most of the remainder was big PRL, and little PRL was present in only small amounts (6-12%) during the luteal phase. During their pregnancies, the serum PRL in subjects A and B initially was mostly big big PRL, but later in gestation the PRL composition shifted from the high mol wt variants to little PRL. The infant's cord (subject A) and peripheral (subject B) serum at birth contained appreciable quantities of big big and big PRL, respectively. These results indicate that structural changes in PRL occur during pregnancy and the menstrual cycle which are probably influenced by the hormonal environment. In addition, the occurrence of larger mol wt PRL species in the serum of the infant of a hyperprolactinemic mother suggests that the presence of high proportions of big big PRL in the serum is genetically determined.

Familial occurrence of big-big prolactin as the predominant immunoreactive human prolactin species in blood.

The occurrence of big-big prolactin (PRL) as the major form of circulating immunoactive PRL has been described in ovulatory hyperprolactinemia. In this study, we have analyzed the heterogeneity of circulating human PRL in 17 members of three families in which one member, bearing galactorrhea-hyperprolactinemic syndrome, was known to have serum big-big PRL as the predominant circulating species. Gel filtration patterns of serum samples of all subjects revealed the presence of significant proportions of big-big PRL in more than one member of the same family, thus suggesting the familial occurrence of big-big as the predominant immunoreactive PRL species in blood.

Effects of Naloxone on pituitary gonadotropins throughout sexual maturation in male and female rats

Con el objeto de conocer los mecanismos por los cuales el sistema opioíde endógeno (SOE) modula la actividad de la unidad hipotálamo-hipofisiaria, se analizaron los efectos de la administración de clorhidrato de naloxona (NAL) sobre la dinámica gonadotrópica de la hipófisis anterior de la rata macho y hembra durante diferentes estadios de la maduración sexual. A ratas Wistar de ambos sexos (de 5 a 50 días de edad) se les administró NAL por vía subcutánea (10 mg/Kg peso) en 0.05 ml de solución salina. Se utilizaron de 5 a 10 animales por grupo de edad incluyéndose igual número de grupos control los cuales recibieron únicamente 0.05 ml de solución salina. Posterior a una hora de la administración de la NAL, los animales fueron sacrificado colectándose la sangre, así como el hipotálamo y las glándulas hipofisiarias. Las concentraciones en suero y contenido hipofisiario de LH y FSH se determinaron por radioinmunoanálisis específicos. El contenido de receptores hipofisiarios de la hormona liberadora de las gonadotropinas (GnRH) se determinó utilizando el análogo sintético del GnRH, D-Ser(TBu6) -des- Gli10 -GnRH-N- etilamida, el cual fue marcado radiactivamente con I-25 utilizando la técnica enzimática de Lactoperoxidasa. Los cambios producidos por la administración de NAL sobre el procesamiento (cambios post-traduccionales) de FSH hipofisiaria fueron estudiados por cromatografía en concanavalina-A obteniéndose la relación libre y unida de FSH a la lectina. Los resultados demostraron que la inhibición del SOE durante etapas prepuberales induce el incremento de las concentraciones en suero de LH y FSH. Este efecto fue estadísticamente significativo únicamente para el caso de las ratas hembras no observándose efectos importantes en ratas del sexo masculino. El incremento de ambas gonadotropinas estuvo acompañado de la depleción de receptores hipofisiarios para GnRh y del incremento de la fracción libre de la hormona folículo estumulante a nivel hipofisiario...

Further evidence that big,big prolactin is preferentially secreted in women with hyperprolactinemia and normal ovarian function.

The heterogeneity of human serum prolactin (PRL) in 12 women with hyperprolactinemia and different derangements of the hypothalamic-pituitary-ovarian axis was studied. The patients were subdivided into three groups: four women with hyperprolactinemia and normal ovarian function (group I), four women with hyperprolactinemia associated with sporadic endometrial bleedings and a positive progestin test (group II), and four women with amenorrhea and a negative progestin test (group III). Gel filtration chromatography of serum samples from patients in group I revealed in three of them that most (80%) of their immunoreactive PRL eluted as big,big PRL (Mr greater than 100,000); whereas the rest of the patients, including those from groups II and III, exhibited a distribution pattern similar to that obtained in normal menstruating women. All PRL species had similar affinities for the antibody, as disclosed by the slopes generated in dose-response curves. These results indicate that ovarian function in hyperprolactinemia might be dependent upon PRL heterogeneity and suggest that big,big PRL may have, under in vivo conditions, a low degree of biologic activity.