Immunohistochemical localization of thyroid hormone in rat thyroid gland.

Direct and indirect immunofluorescence techniques were used to localize the thyroid hormones triidothyronine (T3) and thyroxine (T4) in adult rat thyroid gland. Optimum dilutions of the antisera were established and four tissue fixatives were investigated for usefulness in this technique. Use of antibodies specific for either T3 or T4 resulted in brilliant fluorescence in the colloid pools and apical cytoplasm of follicular cells. In all cases, the adjacent parathyroid gland was devoid of fluorescence. This report demonstrates that these dipeptide hormones can be localized by using immunofluorescence techniques.     

Measurement of thyroid hormone in the rat thyroid gland by radioimmunoassay

The present paper describes (i) a hydrolysis technique with Pronase and leucine aminopeptidase using one rat thyroid gland, resulting in maximum release of thyroid hormones and minimum deiodination, and (ii) a simple and rapid procedure for thyroid hormone radioimmunoassays in thyroid hydrolysates using commercial kits intended for serum thyroid hormone determinations. The procedure is used to determine T4, T3, and rT3 concentrations and hormonal molar ratios in a thyroid gland from a male Wistar rat. The reliability of the method is also studied.     

Effect of thyrotropic hormone on the membrane potential of thyroid gland cells and thyroid hormone secretion with aging

Effect of thyrotropic hormone (TTH) on membrane potential (MP) of thyroid cells and thyroid hormone secretion was studied in experiments on male rats of two age groups (7--12- and 27--32-month-old animals). It was found that during the first 3 hours after TTH administration (5 U/100 g i. v.) the depolarization of secretory cell membranes of adult rats was done pronounced and developed more rapidly than in old ones and that an increase in free thyroxin (T4) correlation with MP changes with time. In a dose of 0.5 U/100 g TTH caused a significant rise in T4 secretion only in old rats. The cAMP level in the thyroid gland declined with aging. In a dose of 5 U/100 g TTH provoked a significant increase in the cAMP content in adult rats and had no effect on its content in old ones. A relationship between the MP level of thyroid secretory cells and thyroid hormone secretion is discussed.     

Functional state of the thyroid gland following exposure to ultrasound

Changes are described in the content of butanol-extracted iodine in the blood serum and total iodine in thyroid tissue of white rat males under ultrasonic effect of various intensity (0.2, 0.6, 1.0 Watt/cm2) and analysed at different time intervals after ultrasound application. A decrease in total iodine content in thyroid glands (at initial level 0.315 mg%) and an increase of butanol-extracted iodine content in the blood serum were observed in all the experimental groups. The data obtained compared with the earlier found increase of the thyroid hormone content in the serum and thyreotropic hormone at a decreased content of thyroxins in the thyroid gland seem to point to the activation of the thyroid function after the application of ultrasound.     

Stimulation by thyrotropin-releasing hormone of vagal outflow to the thyroid gland

An intracerebroventricular (i.c.v.) injection of TRH to the urethane anesthetized rat stimulates the activity of the superior laryngeal nerve (n.sl) which is a vagal ramus terminating at the thyroid gland and adjacent muscles. The response to TRH, a tonic increase in the n.sl outflow, was dose dependent in the 0.005-5.0 micrograms/100 g B.W. range. In contrast to this, methionine-enkephalin (ENK), neurotensin (NT) and somatostatin (SRIF) (5 micrograms/100 g, i.c.v.) all caused a transient decrease in n.sl activity. SRIF showed the highest attenuating effect when injected alone and was capable of diminishing the increased activity produced by a prior injection of TRH. ENK and NT failed to affect the TRH-induced increased activity. When injected concomitantly with TRH, SRIF blocked the response to TRH while ENK and NT both failed to affect the response to TRH. Pretreatment with triiodothyronine for 5 days strongly inhibited the response of the n.sl outflow to TRH. On the other hand, pretreatment with atropine, haloperidol, propranolol, phenoxybenzamine and p-chlorophenylalanine failed to block the stimulating effect of TRH although the response was diminished by some antagonists. It therefore seemed that TRH transmission is involved in central stimulation and SRIF is antagonistic in this regulation of n.sl outflow to the thyroid gland.     

Overlapping effect of thyroid-stimulating hormone and follicle-stimulating hormone on the thyroid gland in baby chicken

Follicle-stimulating hormone (FSH) although quantitatively less effective than thyroid-stimulating hormone (TSH) in the thyroid gland, overlapped with the actions of the latter regarding the indices tested. Thus, it increased the follicular diameter and height of epithelial cells. These findings appear to support our earlier observation demonstrating an overlapping effect of tropic hormones in the gonads and suggest that the overlapping action of tropic hormones with related structure is a general phenomenon in the perinatal period.     

The functional state of the thyroid gland following partial pancreatectomy]

In Wistar rats a study was made of a functional condition of the thyroid gland 1, 6 and 24 hours after partial pancreatectomy. The following signs-served as criteria of a functional condition of the gland: the amount of neutrone-activated iodine in iron, iodine-absorptive capacity of the gland by I131, the amount of protein-bound stable and radioactive iodine in the blood, a morphological condition of the gland structures. It was demonstrated that, despite the initial intensification of the process of synthesis and secretion in the thyroid gland, its secretory activity fell by the end of the experiment. This reduction is regarded as an adaptive response to partial insulin deficiency.