RESUMEN
High local GH-releasing hormone (GHRH) levels are capable of inducing transdifferentiation in salivary cells to synthesize GH. However, the factors implicated in this process remain unknown. To study this subject, normal and Ames dwarf mice were implanted in the submaxillary gland with a slow release pellet releasing 21 microgram GHRH (1-29)-NH(2)/day for 2 months. Control animals received placebo pellets at the same site. After 60 days, heart blood was collected and submaxillary glands were removed. Circulating levels of GH and IGF-I were significantly decreased (P<0.05) in dwarf mice in comparison with controls, and GHRH treatment did not modify either of these two parameters. Controls carrying GHRH pellets showed a significantly higher GH content (P<0.05) in the submaxillary gland than the placebo-treated normal mice. There were no differences between the IGF-I concentrations of placebo- and GHRH-treated salivary tissue from normal mice. Analysis of GH mRNA by RT-PCR followed by Southern blot revealed that GH transcripts were present in the salivary gland samples carrying the placebo pellets in both normal and dwarf mice. The expression of GH was significantly (P<0.05) increased by the GHRH pellets in salivary tissue from normal mice, but not in submaxillary glands from dwarf mice. Pit-1 mRNA was not detected in the GHRH-treated glands of normal and dwarf mice by RT-PCR or by Southern blot. Using these highly sensitive methods, we have been able to detect the transcription of both GH and Pit-1 in pituitaries from Pit-1-deficient Ames dwarf mice. The present experiment demonstrates that salivary tissue synthesizes GH when it is exposed to the influence of GHRH. Both basal and GHRH-induced salivary GH expression appear to be independent of Pit-1.
Asunto(s)
Enanismo/metabolismo , Hormona del Crecimiento/genética , Proteínas de la Membrana , Glándula Submandibular/metabolismo , Análisis de Varianza , Animales , Southern Blotting , Proteínas Portadoras/análisis , Femenino , Hormona del Crecimiento/sangre , Hormona Liberadora de Hormona del Crecimiento/farmacología , Factor I del Crecimiento Similar a la Insulina/análisis , Ratones , Ratones Mutantes , Proteínas de Transferencia de Fosfolípidos , Hipófisis/química , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Glándula Submandibular/químicaRESUMEN
Twelve female rats weighing approximately 150 g received in the submaxillary gland a pellet capable of releasing 3.5 microg GHRH/h for 60 days. Another eight sex- and weight-matched animals received placebo pellets in the same place. After two months the animals were killed, heart blood was collected and pituitary and submaxillary glands were carefully dissected. Pituitary GH content in both placebo- and GHRH-treated animals showed similar values, but plasma GH and IGF-I levels were significantly lower in the animals carrying GHRH pellets (P<0.03); these animals also had a significantly higher GH content in the submaxillary gland (19.2+/-8 ng/mg protein) compared with the placebo-treated group (1.1+/-0.3 ng/mg protein). GH mRNA was present only in the submaxillary gland of GHRH-treated rats as determined by PCR-Southern blot and by in situ hybridization methods. It is concluded that high local GHRH levels are capable of inducing transdifferentiation in submaxillary gland cells to synthesize GH.
Asunto(s)
Hormona Liberadora de Hormona del Crecimiento/farmacología , Hormona del Crecimiento/biosíntesis , Glándula Submandibular/efectos de los fármacos , Glándula Submandibular/metabolismo , Animales , Southern Blotting , Implantes de Medicamentos , Femenino , Hormona del Crecimiento/sangre , Hormona del Crecimiento/genética , Hibridación in Situ , Factor I del Crecimiento Similar a la Insulina/metabolismo , Hipófisis/metabolismo , Reacción en Cadena de la Polimerasa , ARN Mensajero/análisis , Ratas , Ratas Wistar , Glándula Submandibular/químicaRESUMEN
OBJECTIVE: While inferior petrosal sinus (IPS) sampling correctly diagnoses pituitary-dependent Cushing's syndrome if a significant ratio of plasma ACTH between the IPS and the peripheral blood is demonstrated, little has been said about the significance of a negative ratio in Cushing's disease (e.g. a false-negative result). This study evaluates the results of IPS sampling in patients with Cushing's disease, and compares them with both imaging findings and transsphenoidal examination. DESIGN: The results of IPS sampling were retrospectively compared with both imaging findings and transsphenoidal examination. IPS samples were obtained before and 2, 5 and 10 minutes after intravenous administration of 100 micrograms of CRH. PATIENTS: Thirty-two patients with Cushing's disease were evaluated. All subsequently underwent transphenoidal examination of the pituitary gland. MEASUREMENTS: The ratio of the ACTH concentrations at the IPS and in the peripheral blood (IPS:P ratio), and the ratio of the ACTH concentrations between the IPSs (interpetrosal ratio) were calculated. Radiographic evaluation of the pituitary gland was performed with magnetic resonance imaging (MRI, 29 cases) or computed tomography imaging (CT, 3 cases). RESULTS: Transsphenoidal examination of the pituitary gland revealed a microadenoma in 27 cases. Radiological imaging showed a signal compatible with a microadenoma in 22 cases (68.8%), and correctly located the tumour at the side found at surgery in 14 of the 22 cases with positive transsphenoidal findings (MRI 13 cases, CT 1 case, overall 63.6%). Successful bilateral catheterization was accomplished in 30 patients (93.8%). Samples before and after CRH stimulation were drawn in 24 cases. No major complications were observed with the technique. IPS catheterization correctly predicted Cushing's disease (by means of a significant IPS: P ACTH ratio) in 27 of the 30 patients (90%) with basal sampling, and in 23 of the 24 cases with samples drawn before and after CRH administration (95.8%). Taking into account the 12 patients with a lateral microadenoma shown at transsphenoidal examination, IP sinus ACTH ratio was in agreement with the side recorded by the neurosurgeon in 8/12 cases (66.7%). MRI correctly located the tumour in 8/12 patients (66.7%). One patient showed no significant IPS: P ACTH ratio in any set of samples. His MRI showed no sign of a microadenoma. Two years later, another pituitary MRI evaluation showed a midline hypodense signal. The transsphenoidal examination revealed a microadenoma and the post-operative plasma cortisol and urinary free cortisol fell to 293 nmol/l and 100 nmol/24 h, respectively. CONCLUSIONS: Only when a significant IPS:P ACTH ratio is present can Cushing's disease be established by IPS sampling. The absence of a significant IPS: P ACTH ratio does not necessarily imply ectopic secretion of ACTH, nor does it exclude Cushing's disease. The results of lateralization by IPS sampling do not remove the need for a thorough transsphenoidal examination of the contents of the sella turcica.
Asunto(s)
Síndrome de Cushing/diagnóstico , Muestreo de Seno Petroso , Adenoma/diagnóstico por imagen , Adenoma/patología , Adenoma/cirugía , Adolescente , Hormona Adrenocorticotrópica/sangre , Adulto , Hormona Liberadora de Corticotropina , Síndrome de Cushing/sangre , Síndrome de Cushing/cirugía , Reacciones Falso Negativas , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Hipófisis/diagnóstico por imagen , Hipófisis/patología , Hipófisis/cirugía , Valor Predictivo de las Pruebas , Tomografía Computarizada por Rayos XRESUMEN
OBJECTIVE: Previous studies of preoperative pituitary function in patients with craniopharyngioma have been limited in scope and have focused on children. We have evaluated the impact of craniopharyngiomas and their surgical treatment on pituitary function in a large group of mostly adult patients. DESIGN: We performed a retrospective study of patients treated at our centre between 1980 and 1992. PATIENTS: Twenty-two men and 13 women, most of them adults, treated surgically for craniopharyngioma during the above period. MEASUREMENTS: Serum glucose, GH, LH, FSH, TSH and cortisol were measured both before and after a combined insulin induced hypoglycaemia, GnRH and TRH test. Basal concentrations of thyroid hormones, PRL and gonadal steroids were also measured. Preoperative computed tomographic scan was performed in all patients, and a detailed study of visual function before and after surgery was available for 32 of them. Endocrine function was reevaluated post-operatively. RESULTS: In preoperative studies, 29 patients had some anterior pituitary deficit and 13 had diabetes insipidus. The most common abnormality was gonadotrophin deficiency, followed by GH deficiency. Dynamic studies suggested a hypothalamic origin for these deficits. In post-surgical evaluation, impaired pituitary function was observed in most patients. Panhypopituitarism was present in 28 cases and diabetes insipidus in 24. CONCLUSIONS: Our report illustrates the high incidence of endocrine deficits in patients with craniopharyngioma. Additional hypothalamic-pituitary dysfunction usually occurs following surgical treatment of these tumours.