Epidermal growth factor stimulates thyrotropin secretion in the rat.

The present work studied the effects of epidermal growth factor (EGF) on the release of thyrotropin (TSH) and prolactin (PRL) from perifused pituitary glands of 200-gram male Wistar rats. Each pituitary gland, cut into halves, was placed in a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199, pH 7.3, Gibco, USA) from a reservoir to a chamber at a flow rate of 100 microliters/min. Each tightly closed chamber contained one pituitary gland and 600 microliters medium and it was placed in a water bath at 37 degrees C throughout the experiment. One milliliter samples of effluent were collected every 10 min for 60 min to obtain baseline values of TSH and PRL. Thereafter, TSH-releasing hormone (TRH) 10(-8) M or EGF (10(-11), 10(-10), 10(-9) or 10(-8) M) were added to individual chambers and the 10-min sampling of effluent continued for 60 min. EGF 10(-11) M elicited no TSH response, but 10(-10) and 10(-9) M doses induced significant increases in TSH secretion (p < 0.01) with a peak at 10 min after addition of EGF. In another experiment, EGF 10(-8) M or TRH 10(-8) M significantly elevated TSH secretion (p < 0.01). However, TRH, but not EGF, stimulated PRL secretion (p < 0.01). In the in vivo studies, the intravenous administration of EGF 10(-5) M or TRH 10(-5) M both induced significant elevation of TSH release at 10 min after the injection (p < 0.02 for EGF and p < 0.01 for TRH).(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of cold on myocardial mitochondria respiration of rats with hypothyroidism treated with triiodothyronine]. / Efectos del frío sobre la respiración mitocondrial del miocardio de ratas hipotiroideas tratadas con triiodotironina.

The present work studied the effect of cold on oxygen consumption (OC) and alpha-glycerophosphate dehydrogenase activity (alpha-GPD) in heart mitochondria of hypothyroid rats (hypo) treated with T3, T4 or T4 plus Iopanoic Acid (IOP). 200 g male Wistar rats were made hypothyroid by 131I administration. Animals were injected s.c., in divided doses, for 10 days, with one of the following substances: T3, 300 ng/100 g BW/day; T4, 2 micrograms/100 g BW/day or T4 plus IOP, 5 mg/100 g BW/day, for 72 h preceding the experiment. One half of each group was housed in a cold room at 4 degrees C and the other at 22 degrees C, for 25 h, and thereafter decapitated. Heart mitochondria were isolated by routine methods. The OC was measured polarographically using L-malate, L-glutamate and malonate as substrates. Intramitochondrial alpha-GPD activity was measured by a microcolorimetric assay. The results from 16 or 20 rats/group (4 or 5 pools of 4 hearts each) were: In the rats kept at 22 degrees C the OC (in ng at. oxyg./min/mg prot.; State 3) in the hypo+T4 group was 69 +/- 10; in the rats treated with T4+IOP, 75 +/- 11 and in the hypo+T3, 102 +/- 5. When the animals were exposed to 4 degrees C no change was observed in the hypo+T4 and hypo+T4IOP groups. On the other hand, OC was significantly lower in the T3-treated animals (p less than 0.001, versus their controls at 22 degrees C). This group of rats did not survive when exposed to cold.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of epidermal growth factor on thyrotropin secretion in rats]. / Acción del factor de crecimiento epidérmico sobre la secreción de tirotrofina en la rata.

The present work studied the effects of epidermal growth factor (EGF) on the secretion of thyrotropin (TSH) from perifused pituitaries of 200 g body weight male Wistar rats. After decapitation the neural lobe was discarded and the anterior pituitary was transferred to a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199) through a reservoir to a chamber at a flow rate of 100 microliters/min. Individual chambers were filled with 600 microliters of medium and placed in a water bath at 37 degrees C. One ml samples of effluent were collected every 10 min for 60 min to obtain baseline values of TSH. Thereafter, TSH-releasing hormone (TRH) (10(-8) M) or EGF in varied concentrations (10(-8) M to 10(-11) M) were added to individual chambers. The 10 min sampling of effluent was then continued for 60 min to measure TSH by RIA (NIADDK, rTSH RP-2 standard). In the TRH study, the mean basal TSH concentration was 32.1 +/- 6.5 ng/ml, increasing to 105 +/- 13.8 ng at 10 min post-TRH (P less than 0.005) and declining to basal values at 20 min. Addition of EGF 10(-8) M increased TSH secretion from a mean basal value of 68.9 +/- 5.6 ng/ml to 201 +/- 44.3 ng/ml (P less than 0.02) and a return to normal value at 20 min. Similar effects were induced by EGF 10(-9) M (P less than 0.001) and 10(-10) M (P less than 0.05) whereas no effect was elicited by EGF 10(-11) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Acción del factor de crecimiento epidérmico sobre la secreción de tirotrofina en la rata / The effect of epidermal growth factor on thyrotropin secretion in rats

El factor de crescimiento epidérmico (EGF) es un polipéptido de potente acción mitogénica. La probable influencia de esto factor sobre la fisiología del eje hipofiso-tiroideo no ha sido establecida. En el presente trabajo se estudió la acción del EGF sobre la secreción de TSH por hipófisis de ratas Wistar macho in vitro. Cada adenohipófisis fue colocada en una cámara de purifusión conectada a una bomba peristáltica que impulsaba el fluído de perifusión (medio 199, pH 7,3) a un ritmo de 100 *l/min. Cada cámara, conteniendo una hipófisis y 600 *l de fluído de perifusión, fue mantenida en un baño a 37§C. Se obtuvieron muestras del effluente (1 ml cada 10 min.) durante 60 min. para medir TSH basal. Luego se agregó en cámaras individuales, TRH en concentración final de 10-8 M o EGF en concentraciones de 10-8 M a 10-11 M, luego de lo cual se continuócon la colección del efluente cada 10 min. por otros 60 minutos. En cada muestra se midió TSH (ng/ml) por RIA (NIADDK, rTSH-RP 2 standard). Resultados: en el estudio con TRH, la TSH basal promedió 32,1 ñ 6,5 ng/ml con un pico post-TRH de 105 ñ 13,8 ng/ml a los 10 min. (P<0,005), retornando al valor basal ...

Acción del factor de crecimiento epidérmico sobre la secreción de tirotrofina en la rata / The effect of epidermal growth factor on thyrotropin secretion in rats

El factor de crescimiento epidérmico (EGF) es un polipéptido de potente acción mitogénica. La probable influencia de esto factor sobre la fisiología del eje hipofiso-tiroideo no ha sido establecida. En el presente trabajo se estudió la acción del EGF sobre la secreción de TSH por hipófisis de ratas Wistar macho in vitro. Cada adenohipófisis fue colocada en una cámara de purifusión conectada a una bomba peristáltica que impulsaba el fluído de perifusión (medio 199, pH 7,3) a un ritmo de 100 *l/min. Cada cámara, conteniendo una hipófisis y 600 *l de fluído de perifusión, fue mantenida en un baño a 37ºC. Se obtuvieron muestras del effluente (1 ml cada 10 min.) durante 60 min. para medir TSH basal. Luego se agregó en cámaras individuales, TRH en concentración final de 10-8 M o EGF en concentraciones de 10-8 M a 10-11 M, luego de lo cual se continuócon la colección del efluente cada 10 min. por otros 60 minutos. En cada muestra se midió TSH (ng/ml) por RIA (NIADDK, rTSH-RP 2 standard). Resultados: en el estudio con TRH, la TSH basal promedió 32,1 ñ 6,5 ng/ml con un pico post-TRH de 105 ñ 13,8 ng/ml a los 10 min. (P<0,005), retornando al valor basal ... (AU)

Efectos del frío sobre la respiración mitocondrial del miocardio de ratas hipotiroideas tratadas con triiodotironina. / [Effects of cold on myocardial mitochondria respiration of rats with hypothyroidism treated with triiodothyronine]

The present work studied the effect of cold on oxygen consumption (OC) and alpha-glycerophosphate dehydrogenase activity (alpha-GPD) in heart mitochondria of hypothyroid rats (hypo) treated with T3, T4 or T4 plus Iopanoic Acid (IOP). 200 g male Wistar rats were made hypothyroid by 131I administration. Animals were injected s.c., in divided doses, for 10 days, with one of the following substances: T3, 300 ng/100 g BW/day; T4, 2 micrograms/100 g BW/day or T4 plus IOP, 5 mg/100 g BW/day, for 72 h preceding the experiment. One half of each group was housed in a cold room at 4 degrees C and the other at 22 degrees C, for 25 h, and thereafter decapitated. Heart mitochondria were isolated by routine methods. The OC was measured polarographically using L-malate, L-glutamate and malonate as substrates. Intramitochondrial alpha-GPD activity was measured by a microcolorimetric assay. The results from 16 or 20 rats/group (4 or 5 pools of 4 hearts each) were: In the rats kept at 22 degrees C the OC (in ng at. oxyg./min/mg prot.; State 3) in the hypo+T4 group was 69 +/- 10; in the rats treated with T4+IOP, 75 +/- 11 and in the hypo+T3, 102 +/- 5. When the animals were exposed to 4 degrees C no change was observed in the hypo+T4 and hypo+T4IOP groups. On the other hand, OC was significantly lower in the T3-treated animals (p less than 0.001, versus their controls at 22 degrees C). This group of rats did not survive when exposed to cold.(ABSTRACT TRUNCATED AT 250 WORDS)

Acción del factor de crecimiento epidérmico sobre la secreción de tirotrofina en la rata. / [The effect of epidermal growth factor on thyrotropin secretion in rats]

The present work studied the effects of epidermal growth factor (EGF) on the secretion of thyrotropin (TSH) from perifused pituitaries of 200 g body weight male Wistar rats. After decapitation the neural lobe was discarded and the anterior pituitary was transferred to a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199) through a reservoir to a chamber at a flow rate of 100 microliters/min. Individual chambers were filled with 600 microliters of medium and placed in a water bath at 37 degrees C. One ml samples of effluent were collected every 10 min for 60 min to obtain baseline values of TSH. Thereafter, TSH-releasing hormone (TRH) (10(-8) M) or EGF in varied concentrations (10(-8) M to 10(-11) M) were added to individual chambers. The 10 min sampling of effluent was then continued for 60 min to measure TSH by RIA (NIADDK, rTSH RP-2 standard). In the TRH study, the mean basal TSH concentration was 32.1 +/- 6.5 ng/ml, increasing to 105 +/- 13.8 ng at 10 min post-TRH (P less than 0.005) and declining to basal values at 20 min. Addition of EGF 10(-8) M increased TSH secretion from a mean basal value of 68.9 +/- 5.6 ng/ml to 201 +/- 44.3 ng/ml (P less than 0.02) and a return to normal value at 20 min. Similar effects were induced by EGF 10(-9) M (P less than 0.001) and 10(-10) M (P less than 0.05) whereas no effect was elicited by EGF 10(-11) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of thyroxine on oestrogen receptor concentrations in anterior pituitary and hypothalamus of hypothyroid rats.

The effects of thyroxine (T4) were studied on the concentration of oestrogen receptors in the anterior pituitary gland and hypothalamus of ovariectomized euthyroid and hypothyroid rats. A group of rats was made hypothyroid by the administration of 131I. Seven days after ovariectomy, animals were separated into five groups: I, euthyroid controls; II, hypothyroid controls; III, hypothyroid and injected with oestradiol benzoate (10 micrograms/day for 10 days); IV, hypothyroid and injected with T4 (4 micrograms/day for 10 days) and V, hypothyroid and injected with both oestradiol and T4 as described above. In group I, oestrogen receptor levels in pituitary cytosol were 44.4 +/- 3.4 (S.D.) fmol/mg protein and in the nucleus 47.7 +/- 4.0 fmol/mg DNA. In group II the respective values were 12.8 +/- 1.7 fmol/mg protein (P less than 0.01) and 12.7 +/- 1.7 fmol/mg DNA (P less than 0.01 compared with group I). In group III, cytosolic receptor concentrations decreased when compared with those in group II (P less than 0.05), whereas nuclear receptor concentrations rose significantly (P less than 0.01). Group IV had both pituitary cytosolic and nuclear receptors increased (P less than 0.01 compared with group II). In group V there were no changes in cytosolic receptor concentrations but a significant (P less than 0.01) rise in nuclear receptors as compared with group II. Hypothalamic oestrogen receptors in untreated hypothyroid rats (group II) were unchanged in the cytosol and diminished (P less than 0.01) in the nucleus in relation to euthyroid controls (group I). Thyroxine, but not oestrogen, was effective in increasing the concentration of cytosolic receptors (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)