RESUMO
OBJECTIVES: Melatonin and androgens are involved in the regulation of cell proliferation. However, effects of these hormones on pituitary pars distalis (PD) of male viscachas is not fully understood. In the present study, we analysed melatonin and gonadal androgens' effects on proliferating cell nuclear antigen (PCNA) expression. MATERIALS AND METHODS: Pituitary glands from foetuses, immature individuals, prepubertal individuals and adult viscachas during their reproductive cycle, after melatonin administration and after castration, were used. PCNA-ir cells were detected by immunocytochemistry and morphometrically quantified using image analysis. RESULTS: Total percentage of PCNA-ir cells varied seasonally in the adult pituitary, with maximum values during the reproductive period and minima during gonadal regression periods. Percentages of PCNA-ir cells increased after melatonin administration, whereas it decreased after castration. Caudal end and ventral regions were the PD zones which were most affected by seasonal variations and castration. PCNA expression was highest in foetal pituitary from midpregnancy. Numbers of PCNA-ir cells decreased during sexual maturity. CONCLUSIONS: Our results demonstrate the effect of gonadal androgens on cell proliferation during the reproductive period and sexual maturity of these animals. Exogenous melatonin increased PD cell proliferation in adults. Thus, these hormones seem to be involved in different mechanisms that regulate cell renewal of PD in this seasonally breeding rodent.
Assuntos
Androgênios/farmacologia , Proliferação de Células/efeitos dos fármacos , Chinchila/fisiologia , Melatonina/farmacologia , Hipófise/citologia , Hipófise/efeitos dos fármacos , Antígeno Nuclear de Célula em Proliferação/metabolismo , Animais , Castração , Masculino , Hipófise/fisiologia , Hipófise/ultraestrutura , Antígeno Nuclear de Célula em Proliferação/análise , Reprodução , Estações do AnoRESUMO
The anatomy, histology and androgen receptor immunohistochemistry of the prostate (P), seminal vesicles (SV), bulbourethral and coagulant gland (CG) were studied in male viscacha, a seasonally reproductive wild rodent. Two histologically well-defined zones, peripheral and central, were identified in the prostate, according to their relationship with the urethra. The epithelial cells were periodic acid-Schiff (PAS)-positive in the central zone and alcian blue negative in the two zones. The SV are a paired gland, tubular, of tortuous aspect and formed by radial layers. The bulbourethral glands were paired, formed by tubuloalveolar acini and surrounded by a thick layer of skeletal muscle. The CG was multilobulated. The large adenomers showed PAS-positive epithelium and were negative to alcian blue. Androgen receptors in the P, SV and coagulating gland showed variations in their distribution with immunohistochemistry heterogeneous pattern. Finally, the reproductive system accessory glands of male viscacha may be considered as a novel and interesting model for the study of seasonal reproduction in photoperiod-dependent animals.
Assuntos
Glândulas Bulbouretrais/anatomia & histologia , Próstata/anatomia & histologia , Receptores Androgênicos/análise , Roedores/anatomia & histologia , Glândulas Seminais/anatomia & histologia , Sistema Urogenital/anatomia & histologia , Animais , Glândulas Bulbouretrais/química , Células Epiteliais , Imunofluorescência , Masculino , Fotoperíodo , Próstata/química , Receptores Androgênicos/imunologia , Glândulas Seminais/química , Coloração e Rotulagem , Uretra/anatomia & histologia , Sistema Urogenital/químicaRESUMO
New evidence provides valuable information about the participation of sustentacular cells in chromaffin cell catecholamine secretion. In this process, calcium ions play an important role. It has been shown that there is an intense ionic traffic between both types of cells. Moreover, sustentacular cells take an active part in calcium metabolism, regulating levels of the ion and indirectly, the synthesis and release of catecholamines. This background information encouraged us to study the sustentacular population of Lagostomus adrenal medulla and its morphologic relationship with the chromaffin population. The animals were captured, transported to the animal facilities, anaesthetized and killed. The adrenal gland was processed by immunohistochemistry using antiserum against S-100 (subunit alpha and beta), a specific marker. Through the morphological and immunohistochemical study, it was found that there are sustentacular cells in deferent regions of adrenal medulla, mainly in the basal zone of chromaffin cells, which constitute the glomerular structure around blood capillaries. Cytoplasmic extentions of sustentacular cells penetrate into chromaffin cells and make contact with the basal membrane of the capillary endothelium. The relationship among chromaffin cells, capillaries and sustentacular cells suggests that they may intervene actively in the adrenal medulla metabolism.
Assuntos
Medula Suprarrenal/citologia , Células Cromafins/metabolismo , Roedores/anatomia & histologia , Medula Suprarrenal/anatomia & histologia , Medula Suprarrenal/metabolismo , Animais , Cálcio/metabolismo , Catecolaminas/metabolismo , Imuno-Histoquímica/veterinária , MasculinoRESUMO
Somatotrophs were identified and quantified in pituitary pars distalis of male viscachas (Lagostomus maximus maximus) during the annual reproductive cycle, after the administration of melatonin, after castration and in different growth stages by immunohistochemistry and morphometric analysis. In adult male viscachas, the somatotrophs were distributed throughout the pars distalis during the reproductive cycle. They were oval, pyramidal or round in shape with a large round nucleus. The percentage immunopositive area, the major cellular diameter and the number of cells decreased during the gonadal regression period in relation to the values found in the reproductive period. The administration of melatonin did not provoke any variations of the morphometric parameters studied. On the contrary, a significant decrease in the percentage immunopositive area, in the major cellular diameter and in the number of somatotrophs in castrated viscachas was observed. The study of different growth stages showed that these morphometric parameters increased from immature to adult animals in the reproductive period. The results obtained suggested that the variations of the morphometric parameters of somatotrophs are more related to the gonadal development and activity than to a direct effect of melatonin.
Assuntos
Hormônio do Crescimento/análise , Adeno-Hipófise/citologia , Neuro-Hipófise/citologia , Hormônio Adrenocorticotrópico/análise , Animais , Argentina , Chinchila , Escuridão , Imuno-Histoquímica , Luz , Hormônio Luteinizante/análise , Masculino , Adeno-Hipófise/anatomia & histologia , Neuro-Hipófise/anatomia & histologiaRESUMO
The gonadotropes, LH and FSH cells, were immunohistochemically identified in the pituitary pars distalis of the adult male viscacha (Lagostomus maximus maximus) using specific antibodies against hLHbeta and hFSHbeta with the streptavidin-biotin-peroxidase complex. The distribution, size and percentage immunopositive area of these cells were analyzed by image analysis in viscachas captured during the annual reproductive cycle and after the chronic administration of melatonin. The LHbeta and FSHbeta cells showed seasonal changes in the distribution, size and percentage immunopositive area. The LHbeta cells were found widely distributed throughout the pars distalis during the reproductive period, and they were found in the ventro-medial region in the pars distalis during the gonadal regression and gonadal recovery periods. The LHbeta cells reached the largest size and immunopositive area during the reproductive period and the smallest size and immunopositive area during the gonadal regression period. The FSHbeta cells were found in the ventro-medial region during reproductive and gonadal regression periods. The FSHbeta cells were found widely distributed throughout the pars distalis during the gonadal recovery period when they showed the maximum percentage immunopositive area. A decrease in the size of LHbeta and FSHbeta cells was observed after the chronic administration of melatonin. Moreover, it produces a decrease in the immunopositive area occupied by the LHbeta cells but not in the immunopositive area occupied by the FSHbeta cells. Our results show great activity of LHbeta and FSHbeta cells in different moments of the annual reproductive cycle demonstrating that these cells do not secrete in parallel. Moreover, melatonin acts differentially on the activity of the gonadotrope cells.