Effect of insulin-like growth factor-I gene therapy on the somatotropic axis in experimental prolactinomas.

Insulin-like growth factor-I (IGF-I) provides a physiologic feedback effect within the somatotropic axis. Gene therapy was implemented in young female Sprague-Dawley rats which received 2 pituitary stereotaxic injections of a control recombinant adenoviral vector expressing green fluorescent protein (RAd-GFP) or IGF-I (RAd-IGF-I). The animals were sacrificed 7 days after injection. Previously, on day -23, the experimental groups received subcutaneous implants of 17-beta estradiol. Morphometric analysis revealed that the somatotrope cells in estrogen-treated rats without stereotaxic injections showed a significant (p < 0.01) increase in the cell size compared with intact controls (59.9 +/- 1.1 vs. 42.9 +/- 1.2 microm(2)) and had a significant (p < 0.05) decrease in cell density with respect to intact animals (10.5 +/- 0.1 vs. 19.7 +/- 1.7). The treatment of pituitary adenomas with RAd-IGF-I induced a significant (p < 0.05) decrease in cell size with respect to E(2) + RAd-GFP (51.3 +/- 0.3 vs. 58.9 +/- 0.3 microm(2)) and no changes in cell density compared with RAd-GFP-injected animals (12.8 +/- 1.7 vs. 10.5 +/- 0.1). Serum growth hormone was higher (p < 0.01) in estrogen-treated animals versus controls (146.7 +/- 6 vs. 73.9 +/- 9 ng/ml). In rats carrying estrogen-induced adenomas, RAd-IGF-I injection induced a significant (p < 0.05) decrease in serum growth hormone compared to RAd-GFP-injected animals (107.5 +/- 7 vs. 142.4 +/- 9 ng/ml). IGF-I gene therapy appears to be an effective approach for the treatment of experimental somatomammotropic pituitary tumors and could be potentially useful as an adjuvant of conventional therapies.

Morphometric assessment of the impact of serum thymulin immunoneutralization on pituitary cell populations in peripubertal mice.

Thymulin is a thymic hormone involved in several aspects of intra- and extrathymic T-cell differentiation. Thymulin also possesses hypophysiotropic activity which suggests that this metallopeptide may play an important role in thymus-pituitary communication, particularly during early life. The aim of the present study was to evaluate the impact of serum thymulin suppression from birth to peripuberty on the morphology of different pituitary cell populations in prepubertal C57Bl/6 mice. Animals were submitted to immunoneutralization of circulating thymulin from postnatal day 1 to the end of the study (age 32 days). From their 1st day of life, the animals were submitted to a protocol of intraperitoneal injections of rabbit anti-thymulin serum (alpha-FTS) and normal rabbit serum (NRS) in the controls. On their 33rd day of life, the animals were killed and their pituitaries were immediately dissected, fixed and immunostained using the EnVision system with primary antibodies against growth hormone, thyrotropin, corticotropin, gonadotropins and prolactin. Morphometry was performed by means of an image analysis system. The following parameters were calculated: volume density = Sigma cell area/reference area (RA); cell density (CD) = number of cells/RA, and cell size (expressed in microm2). Serum thymulin was measured by a rosette bioassay while pituitary hormones were assayed by radioimmunoassay. Serum prolactin, luteinizing hormone, follicle-stimulating hormone, growth hormone and thyroid-stimulating hormone were significantly lower in the alpha-FTS animals of either sex compared with the corresponding NRS counterparts. The somatotrope, lactotrope and corticotrope populations showed a significant decrease in CD, while cell hypertrophy was observed in some of the pituitary cell populations of the alpha-FTS group compared to the NRS group. In the alpha-FTS group, there were sex differences in the morphometric changes observed. Our results suggest that serum thymulin plays a significant role during early life in the postnatal maturation of endocrine cells of the mouse anterior pituitary gland.

Relationship between pituitary and adipose tissue after hypothalamic denervation in the female rat. A morphometric immunohistochemical study.

Neonatal administration of monosodium glutamate (MSG) to rats produces severe lesions in certain hypothalamic nuclei, with repercussions in different neuroendocrine axes, and serves as a model for their study. In addition, adipose tissue, as a target organ, is known to be directly related to several neurondocrine axes. We used 21-day-old female Sprague-Dawley rats that had received a neonatal treatment with MSG (4 mg/g body weight, i.p., from day 2 up to day 10 of age) in addition to control rats (injected with 10% NaCl solution, on a similar schedule). We performed a specific immunohistochemical study on each anterior-pituitary cell population, along with the morphometry of these cells and of the parietal and visceral adipose tissue, and measured the levels of serum leptin and triglycerides. The MSG animals evinced significant changes in volume density (VD), cell density (CD), and cell size (CS) in the corticotropes, thyrotropes, and LH gonadotropes, but not in the somatotropes, lactotropes, and FSH gonadotropes. The modification common to the three cell types was a hyperplasia, but with different results depending on cell size. Furthermore, in the MSG rats significant changes were also observed in the VD, CD, and CS of the adipose tissue, consisting of adipogenesis and decrease of adipocyte size in visceral fat, together with probable lipogenesis as judged by an increase in adipocyte size in the parietal fat. The serum levels of leptin and triglycerides appeared significantly higher in MSG animals. For the first time in this animal model, and at the level of three neuroendocrine axes, our results suggest changes that correlate hypothalamic damage, cellular pituitary alterations, and the response of the adipose tissue as a target organ for MSG insult.