ABSTRACT
Stress in pregnant rats alters the pattern of secretion of corticosterone (COR) and modifies transplacentally hypothalamic-pituitary-adrenal axis (HPA) fetus. Prenatal stress during the critical hypothalamic differentiation is related to decreased fertility of male offspring by an increase in the basal level of COR. This modification could induce long-term changes in the process of apoptosis in the testis. However, early postnatal handling increases maternal behavior and could reverse the effects caused by increased secretion of COR. The aim of this research was to investigate the effects of early postnatal stimulation of male rats prenatal stressed by chronic immobilization during the last two weeks of pregnancy, on the hypothalamic-pituitary-gonadal axis and their relationship with the activity of the HPA. Male Wistar rats 3 month olds, were separated in four groups: (a) prenatally stressed animals by immobilization (IMO), without postnatal stimulation; (b) prenatally stressed animals with postnatal stimulation; (c) control animals without prenatal stress, without postnatal stimulation and (d) control animals without prenatal stress, with postnatal stimulation. In different animals groups plasmatic levels of COR, Testosterone (T) and Luteinizing Hormone (LH) were analyzed. Gonadosomatic index and testicular apoptosis was determined. In conclusion that prenatal stress by IMO increased levels of COR and inhibits the HHG axis obtaining low values of plasmatic LH and T, testicular weight, and induction of apoptosis in testes. On other hand, early postnatal stimulation results in an increase in maternal care to the offspring reversing the effects of prenatal stress on the HPG axis. This effect could be mediated by a mechanism independent of the HPA axis.
El estrés en ratas preñadas altera el patrón de secreción de corticosterona (COR) materna la cual, por vía transplacentaria, produce una alteración del eje Hipotálamo-Hipófiso-Adrenal (HHA) fetal. El estrés prenatal producido durante la etapa crítica de diferenciación hipotalámica, está relacionado con la disminución de la fertilidad en las crías macho, por un aumento en el nivel de COR basal. Esta modificación podría inducir cambios a largo plazo en el proceso de apoptosis testicular. Sin embargo, la estimulación postnatal temprana mejora el comportamiento materno, revirtiendo las alteraciones producidas por el aumento de COR en las crías adultas. El objetivo fue investigar el efecto de la estimulación postnatal temprana sobre el eje Hipotálamo-Hipófiso-Gonadal (HHG) en ratas macho estresadas prenatalmente (EP), por inmovilización crónica durante las dos últimas semanas de la preñez. Se utilizaron crías de 3 meses de edad, que fueron divididas en 4 grupos: (a) individuos EP y sin estimulación postnatal; (b) individuos EP con estimulación postnatal; (c) individuos controles no estresados prenatalmente (CP) y sin estimulación postnatal; y (d) individuos CP con estimulación postnatal. En todos los grupos se midió COR, Testosterona (T) y Hormona Luteinizante (LH). Se determinaron la apoptosis y la Caspasa 3 testicular y el índice gonadosomático. Se concluye que el estrés prenatal por inmovilización aumenta los niveles de COR del eje HHA e inhibe el eje HHG obteniendo valores bajos de LH y T plasmáticas. Se observa disminución del tamaño testicular y aumento de la apoptosis de las células testiculares. Por otro lado, la estimulación postnatal temprana se traduce en un aumento del cuidado materno hacia la cría, lo que revierte los efectos producidos por el estrés prenatal sobre el eje HHG. Este efecto podría estar mediado por algún mecanismo independiente del eje HHA.
Subject(s)
Male , Animals , Female , Pregnancy , Rats , Hypothalamo-Hypophyseal System , Prenatal Exposure Delayed Effects , Stress, Physiological , Apoptosis , Physical Stimulation , Rats, WistarABSTRACT
Prenatal stimulations have been shown to have long-term effects on at reproductive activity. We evaluated the influence of the prenatal stress on the hypothalamic-pituitary-gonad (HPG) axis in male offsprings from mothers with high number of offsprings per litter (HNL) and low number of offsprings per litter (LNL) after hypothesizing that the number of offsprings per litter may modify the effect of the prenatal stress on the HPG of adult offsprings. Pregnant Wistar rats were used for this study. Immobilization (IMO) stress was used, 30 min, 3 times per week, from the 5th to 21st day of pregnancy. The weight of adrenal and gonads, and the corticosterone (COR), testosterone (TES) and luteinizing hormone (LH) plasmatic levels were analyzed in the male offspring at 30, 45 and 70 days of age. The offspring males coming from LNL showed a decrease in testicle weight and TES levels, without changes in the plasmatic LH levels. However, the offspring of HNL showed a decrease of LH levels. It is possible to conclude that in LNL prenatal stress would produce alterations to gonadal level, while in HNL the effect of stress would be evident at pituitary level.
Subject(s)
Animals , Male , Female , Pregnancy , Rats , Corticosterone/blood , Pituitary Gland/physiology , Hypothalamus/physiology , Luteinizing Hormone/blood , Sexual Maturation , Stress, Physiological , Testis/physiology , Prenatal Exposure Delayed Effects/etiology , Litter Size , Rats, Wistar , Testosterone/bloodABSTRACT
The chronic stress induces functional adaptations in the hypothalamo-pituitary- adrenocortical (HPA) and in the sympathetic-medullary-adrenal axis (SAM). Both axis are considered vital regulators of the homeostasis in vertebrates (Seyle, 1936; Ostrandrer et al, 2006. On the other hand, the placenta provides highly specialized functions during gestation that are critical for the normal development of the embryo/fetus (Soares et al., 1991). We hypothesized that the chronic immobilization (IMO) stress in pregnancy rats produces alterations in prolactin concentrations in placental tissue and also changes in the response of SAM axis. Chronic stress by IMO was applied on days 12, 17 and 21 of pregnancy rats. Relative concentrations and localization of placental lactogen-II (PL-II) and the PRL- like protein A (PLP-A) in chorioalantoic placenta were estimated by Immunoblotting and Immunocytochemical analysis. The levels of catecholamines metabolite, acid 3-metoxi 4-hidroximandélico (VMA), were analyzed in stressed rats urines on 6,12,17,21 days of pregnancy, by HPLC, in order to determine the response of SAM axis. During the days of the pregnancy studied, chronic stress did not induce any changes neither in the localization nor in placental concentrations of PL-II and PLP-A. The VMA values in stressed mothers urines increased on the day 6 respecting the control ones at the same time of pregnancy. VMA values in stressed rats at 21 days of pregnancy are smaller than the respective controls. We conclude that the chronic stressed mothers activated the SAM axis at the beginning of pregnancy and then they diminished the metabolites catecholamines that were interpreted as a stress adaptation coincident with normal concentrations of both placentary prolactines at this stage of the pregnancy.
El estrés crónico induce adaptaciones funcionales en los ejes hipotálamo-pituitario-adrenal (UPA) y en el simpático médulo adrenal (SAM). Ambos ejes son considerados reguladores vitales de la homeostasis en los vertebrados (Seyle, 1936; Ostrandrereí al., 2006). Por otro lado, el desarrollo y crecimiento fetal de los mamíferos dependen en gran medida del buen funcionamiento de la placenta (Soares, 1991). Nosotros hipotetizamos que el estrés crónico por inmovilización (IMO) aplicado a las ratas gestantes produce alteraciones en las concentraciones de las prolactinas en el tejido placentario y cambios en la respuesta del eje SAM. Se le aplicó estrés crónico por IMO a las hembras en los días 12, 17 y 21 de la preñez y se analizó por inmunocitoquímica e inmunoblotting la localización y concentraciones del lactógeno placentario dos (PL-II) y la proteína A ligada a la prolactina (PLP-A) en la placenta. Se analizaron por HPLC, en las orinas de ratas preñadas (6,12,17,21 días), los niveles del metabolito de las catecolaminas, (ácido 3-metoxi 4-hidroximandélico) (VMA), a fin de determinar la respuesta del eje SAM al tratamiento. El estrés crónico no indujo cambios tanto en la localización como en las concentraciones de PL-II y PLP-A en las placentas en los días de la preñez estudiados. Los valores de VMA en las orinas de las madres estresadas se incrementaron en el día 6 con respecto al control del mismo tiempo de preñez. Mientras que a los 21 días los valores de VMA de las ratas estresadas son menores que los controles respectivos. Concluimos que en las madres estresadas crónicamente, no se alteraron las concentraciones de ambas prolactinas placentarias. En cambio se activó el eje SAM al comienzo de la preñez ante el primer estímulo estresante y luego una reducción de la respuesta del eje ante el estrés crónico, a medida que avanza la preñez.
ABSTRACT
Chronic stress by immobilization during gestation can alter several mechanisms that maintain homeostasis in adrenal gland. The aim of this work was to quantify the apoptotic index of adrenal cortex during mid-pregnancy and to prove cytological characteristics by electron microscopy. The apoptotic index did not present significant differences between the adrenal cortex areas of control and experimental rats in any of the three ages studied. The day of gestation influenced significantly on the apoptotic index in both groups. This index increased as gestation progressed. It may be concluded that chronic stress by immobilization might induce the increase of apoptotic index in adrenal cortex as gestation progresses which might be related variations of plasmatic corticosterone and prolactin, and to the decrease of specific growth factors. On the other hand, it might be concluded that each zone of adrenal cortex behaves independently in regards to apoptosis and cellular proliferation via paracrine and/or autocrine regulatory mechanisms without being affected by other zones.