ACTH radioimmunocytochemistry (RICH) on rat anterior pituitary cells

A rapid and sensitive radioimmunohistochemical assay for quantitation of vasopressin in discrete brain regions with an anatomical resolution

Radioimmunoassay has become a widely used method to study different neuroactive substances from brain tissue extracts, but cannot provide anatomical resolution. Here we describe a simple and sensitive radioimmunohistochemical assay (RIHA) to quantify a peptide, vasopressin (VP), in discrete brain regions of rats with 3-day water deprivation. After decapitation, brains were removed, frozen with dry ice and cut into 14-microns cryostat sections which were then fixed with 4% paraformaldehyde in phosphate-buffered saline. After rinses, tissue sections were stored in a freezer until use. For RIHA, brain tissue sections were pre-incubated, and then incubated with rabbit vasopressin antibody (1:2000 dilution) for 24 h at room temperature. After rinses, sections were incubated with 125I-labeled goat antirabbit IgG (1:200 dilution) for 1 h. Specimens were processed for quantitative autoradiography after rinses and drying. RIHA with aid of a computer-assisted image analysis system revealed that the VP content was significantly reduced in the paraventricular hypothalamic nucleus (PVN) and supraoptic nucleus (SON) of rats with 3-day water deprivation, whereas a parallel in situ hybridization study further demonstrated that VP mRNAs in the PVN and SON were greatly increased. In summary, this experiment demonstrates that RIHA is a simple and powerful tool which is able to detect changes of VP in the hypothalamus of dehydrated rats. Combining this method with in situ hybridization to assess mRNA expression allows assessment of the functional significance of the peptide changes. In this case, dehydration depletes vasopressin and upregulates its synthesis. Therefore, the combined use of RIHA and in situ hybridization should have general applicability to evaluate the functional role of a peptide or neurotransmitter system in response to stimuli in a quantitative way with anatomical resolution.

Ultrastructural morphometry of the rat pituitary intermediate zone after stimulation and suppression

The intermediate zone of the rat pituitary was studied after stimulation for 3 weeks with the adrenostatic drugs metyrapone and aminogfutethimide and after suppression for 3 weeks with the glucocorticoid 6α-methylprednisolone using morphometry by the point-counting method on electron micrographs. After metyrapone, intermediate cells showed a significant (P <.05) increase in volume percentages of the smooth endoplasmic reticulum, the Golgi apparatus, and the lucent immature secretory granules, as well as a significant decrease in the lucent secretory granules, the vacuoles, the lysosomes, and the cell membranes in comparison with the untreated controls. After aminoglutethimide, the volume percentages of the nuclei, the smooth endoplasmic reticulum, and the dense and lucent immature secretory granules were significantly increased in comparison with the controls, whereas the unorganized cytoplasm, the lucent secretory granules, the vacuoles, and the lysosomes were significantly decreased. The morphological changes after both adrenostatic drugs clearly indicate the pathophysiologically expected increase of secretory activity. After 6α-methyfprednisolone, the rough endoplasmic reticulum, the vacuoles, and the lysosomes significantly decreased in comparison with the controls, and the smooth endoplasmic reticulum, the Golgi fields, and the immature secretory granules were increased. These changes cannot be interpreted without certain reservations as the first alterations indicate decreased activity, whereas the increased Golgi fields and immature secretory granules are usually signs of increased secretory activity, which cannot be expected after glucocorticoid treatment. The possible causes are discussed.