Electronic Library of Scientific Literature


Volume 29 / No. 3 / 1995

Distribution of Thyrotropin Releasing Hormone Receptor in Rats: An Immunohistochemical Study


The Fourth Department of Internal Medicine, Laboratory Medicine and First Department of Physiology, Aichi Medical University, Nagakute, Aichi, Aichi 480-11, Japan
and Department of Internal Medicine Konanshowa Hospital, Konan Aichi, Japan

Thyrotropin releasing hormone (TRH) receptor was identified immunohistochemically in the rat tissues using anti-peptide antiserum. Anti-TRH receptor antiserum was raised in New Zealand white rabbits immunized with a conjugate of synthetic TRH-receptor peptide (15-28) to bovine serum albumin. Immunohistochemical analysis was performed by the avidin-biotin complex method. TRH-receptor immunoreactivity was visualized in the central nervous system and anterior pituitary thus supporting previous investigations of TRH receptor distribution using in vitro autoradiographic ligand binding. Significant stain was detected in neural perikarya, axons and dendrites as well as in many cells of the retina, adrenal medulla, stomach mucosa, Auerbach's nervous branch and Mysner's nervous branch of the stomach, small intestine and colon. When using antiserum preincubated with synthetic TRH-receptor peptide (15-28) or rat anterior pituitary homogenate which contains TRH-receptor peptide, no significant stain of the anterior pituitary cells or neurons in the hypothalamus was detected. These findings suggest that TRH-receptor is widely distributed and that this method is valuable in studying the distribution of TRH-receptor in rats.

Key words: Thyrotropin Releasing Hormone - Receptor - Rat - Immunohistochemistry
pp. 129-134

Circadian Variations in Serum Levels of LH, FSH, Estradiol, Testosterone and Sex Hormone Binding Globulin in Acromegalic Women with Menstrual Disturbances Before and After Transsphenoidal Adenectomy


1st Department of Pathophysiology and Clinical Biochemistry, Silesian Academy of Medicine, 41-800 Zabrze, Poland

Day/night profiles of serum GH, PRL, IGF-I, LH, FSH, testosterone (TT and FT), estradiol (E2) and SHBG were estimated in 12 acromegalic women with GH- and PRL-producing pituitary adenomas and 13 patients with GH-secreting pituitary tumors before and 3 months after transsphenoidal adenectomy. All the subjects studied have had irregular menstrual cycles. Blood for profile determinations was drawn from a peripheral vein at 3 h intervals for three 24 h periods (starting at 08.00). Before surgery all acromegalic women had high mean 24 h GH and IGF-I levels (with irregular peaks) even in the absence of hyperprolactinemia. Postoperative mean 24 h GH level was still high only in 5 out of 25 women studied, and that of IGF-I in 10 of these patients. In 12 acromegalic women with preoperative hyperprolactinemia and disturbed 24 h fluctuations postoperative 24 h mean level of PRL and its circadian rhythm were normal. Before surgery, the circadian variations of pituitary-sex hormone levels and SHBG capacity in serum were not impaired. However, mean 24 h levels of LH, FSH, TT, FT E2 and SHBG were altered mainly in patients with mixed type of GH and PRL producing adenomas. This may be related to the increased activity of GH/IGF-I axis on the one hand and to the excess of PRL on the other. The postoperative normalization of pituitary-sex hormone levels and SHBG capacity in serum was noted only in women with normal 24 h circadian variations of IGF-I levels.

Key words: Acromegaly - GH - PRL - IGF-I - LH - FSH - TT - FT - E2 - SHBG - Circadian Rhythm - Transsphenoidal Adenectomy
pp. 135-149

Treatment with Triiodothyronine (T[3]) against Multinodular Goiter Fails to Prevent the Onset of Graves' Disease


1 Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Japan
2 The Third Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, Japan

We report two cases who developed hyperthyroidism and positive thyroid stimulating antibody (TSAb) while they were treated with T[3] under the diagnosis of follicular adenoma of thyroid for four or eleven years, respectively. In both cases thyroid scintigraphy revealed an increased radioiodine uptake with multinodular defects. The uptake of ¹³¹I was not suppressed by the administration of T[3]. Histological examination showed encapsulated nodule surrounded by diffuse hyperplasia. TBII or TSAb appeared in accordance with increased plasma levels of T[3] and T[4]. In spite of suppressed TSH the appearance of TSAb and subsequent manifestations of Graves' disease suggested that T[3] failed to prevent the immune mechanism which was involved in the production of TSAb.

Key words: Multinodular Goiter - Graves' Disease - TBII - TSAb - Follicular Adenoma
pp. 151-156

The Effect of Early Weaning on Insulin Receptors in Rat Liver


Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia.

The effect of early weaning on insulin binding was studied in rat hepatocytes. Early weaned rats were separated from lactating females on the 18th postnatal day, control animals were maintained with dams up to the 30th day. Plasma insulin and glucose levels, insulin binding capacity of isolated hepatocytes were determined at the age of 18, 22, 30 and 120 days. In some age groups a body mass and also insulin degradation by hepatocytes were determined.
A decrease of plasma insulin and glucose level was found in 22day old early weaned rats as compared to 18 day old rats and to controls of the same age. A decrease of body mass was found in early weaned rats during the first week after weaning. An increase of insulin binding was observed in hepatocytes from 18 to 30 dayold control rats. However, in early weaned animals a highly significant elevation of insulin binding capacity was found in 22 dayold rats. At the age of 30 and l20 days no significant differences in insulin binding capacity of hepatocytes between early weaned and control rats were noted. A decrease of insulin degradation was observed in 22 dayold early weaned rats. These results showed that early weaning affects the glucose homeostasis and insulin binding capacity of rat hepatocytes.

Key words: Rat Hepatocytes Early Weaning Insulin Binding
pp. 157-162

Vasopressin and Oxytocin Release as Affected by Constant Light in Pinealectomized Male Rats


Department of Pathophysiology and ¹Department of Physiology, Institute of Physiology and Biochemistry, Medical University, Lodz, Poland

The effect of continuous lighting on vasopressin (AVP) and oxytocin (OT) levels in the hypothalamus, neurointermediate lobe (NIL) and blood plasma was studied in normal, sham operated and pinealectomized male rats.
Under normal light conditions (L:D 12:12) the OT and AVP content in the hypothalamus and the NIL was not changed 8 days after pinealectomy, but it was significantly diminished 8 weeks after the surgery.
When normal animals were exposed to constant light for 8 days, the AVP and OT content in the hypothalamus and NIL was significantly diminished, whereas plasma OT level was increased. Exposure of pinealectomized animals to constant light for 8 days resulted in the diminution of neurohypophysial AVP as well as OT but did not change significantly the hypothalamic and plasma levels of both hormones.
Exposure of animals with intact pineal gland to the constant light for 8 weeks did not change the OT and AVP levels in the hypothalamo-neurohypophysial system and in the blood plasma. After pineal removal, however, the pinealectomy-induced decrease of OT and AVP content was not observed in the hypothalamus, whereas the plasma level of both hormones was even higher than that observed in not-pinealectomized animals kept at constant light conditions.
These results suggest that the response of vasopressinergic and oxytocinergic neurons to continuous lighting is changing when the time of exposure of animals to such conditions is prolonged; these effects depend on the presence of intact pineal gland.

Key words: Vasopressin - Oxytocin - Pinealectomy - Rats - Constant Light
pp. 163-170

Ecdysone Regulated RNA Synthesis in Drosophila Larval Salivary Glands


Institute of Experimental Endocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovak Republic

The changes in total and ribosomal RNA (rRNA) synthesis in cultured larval salivary glands of Drosophila in response to steroid hormone ecdysone have been studied. By using the incorporation of [³H]-uridine or [³²P]-UTP into salivary gland cells, followed by RNA extraction and electrophoretic or sucrose gradient fractionation it was found that physiological concentrations of ecdysone stimulate the synthesis of rRNA. Administration of selective transcription inhibitors (actinomycin D, alpha-amanitin, cordycepin, DRB, and 5- fluorouridine) as well as protein synthesis inhibitors (cycloheximide, puromycin) showed that early response to ecdysone involved a direct stimulation of rDNA transcription, probably by ecdysone-ecdysone receptor complex, and is independent of protein synthesis. In later stages of the response to ecdysone, as revealed again using transcription and protein synthesis inhibitors, the synthesis of rRNA is dependent on the factor(s) produced during early stages of the response, in the manner which is very similar to sequential gene activation in chromosomal puffs. Experiments with the withdrawal of ecdysone from culture medium in early stages of its action show similar negative effects on rRNA synthesis as inhibitors of RNA polymerase II, thus proving the existence of parallel mechanism controlling induction of specific chromosomal puffs and transcription of rDNA. The data presented suggest that, in addition to the expression of tissue and developmentally-specific genes, the regulation of rDNA transcription, along with the production of ribosomes, might be required for Drosophila metamorphosis. The results are discussed in the light of vertebrate's steroid hormone action on ribosomal genes.

Key words: RNA Synthesis - Ribosomal RNA - Ecdysone - Drosophila - Metamorphosis
pp. 171-185