Immunoreactive thyroid stimulating hormone (TSH): Association with synaptosomally-rich fractions in the rat hypothalamus

Hojvat, Sally; Anderson, John M.; Nishimura, Nancy F.; Baker, George P.; Kirsteins, L.; Lawrence, A. M.

doi:10.1016/0006-8993(83)90340-2

Cited by 15 publications

(15 citation statements)

References 16 publications

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“…Similar subcellu lar distribution has been reported for several CNS peptides including hypothalamic TSH [10] and melanocyte-stimulat ing hormone (MSH) [2].…”

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confidence: 72%

“…Dissected hypothalami, in groups of 12, approximately 700 mg, were immediately placed in iced saline and the further preparative procedure was slightly modified from that described by DeRobertis et al [4]. Once the dissections were com pleted, batches of 12 hypothalami were homogenized in 10 ml of 0.32 M sucrose 10 pA/ CaCh, 0.01 M phosphate-buffered saline (PBS) at 4 °C, for I min using a glass Potter homogenizer with a fairly loose-fitting Teflon plunger.…”

Section: Methodsmentioning

confidence: 99%

“…Both content and concentration of LH in the nuclear pellet, Pi, were substantially lower. These findings provide further framework for speculation on the role of brain-based LH.We have previously reported the presence of immunoas sayable and bioassayable luteinizing hormone (LH) [7,8,13], growth hormone (GH) [11,13,20], and thyroid-stimulat ing hormone (TSH) [10,12,13] within certain areas of the rodent central nervous system (CNS) and have alluded to the origin [7,11,12], developmental profile [13], and possible role of these substances in neuroendocrine physiology [8], Using a sensitive and specific radioimmunoassay (RIA) for rat LH [7,8,13] and a standardized procedure for subcellu lar fractionation of neuronal tissue [4], we have found that particle-bound hypothalamic LH is preferentially asso ciated with synaptosomally rich fractions. Similar subcellu lar distribution has been reported for several CNS peptides including hypothalamic TSH [10] and melanocyte-stimulat ing hormone (MSH) [2].…”

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confidence: 99%

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Subcellular Localization of Hypothalamic Luteinizing Hormone

Emanuele¹,

Lipov²,

Anderson³

et al. 1985

Neuroendocrinology

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Ultracentrifugation and sucrose gradient separation techniques have been applied to study of the subcellular distribution of hypothalamic luteinizing hormone (LH). Subcellular particle-bound LH accounted for 42% of the total LH while cytoplasm contained 58% of the total immunoassayable LH in these extracts. 70% of particle-bound LH was present in the P₂ fraction and most of the particle-associated LH was found in subfractions of P₂ rich in synaptosomes but poor in myelin and mitochondria. While actual amounts of LH in the P₃ and P₄, the microsomal fractions, were relatively small, the concentration of LH, expressed as nanograms per milligram of protein was quite high. Both content and concentration of LH in the nuclear pellet, P₁, were substantially lower. These findings provide further framework for speculation on the role of brain-based LH.

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“…Similar subcellu lar distribution has been reported for several CNS peptides including hypothalamic TSH [10] and melanocyte-stimulat ing hormone (MSH) [2].…”

mentioning

confidence: 72%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Subcellular Localization of Hypothalamic Luteinizing Hormone

Emanuele¹,

Lipov²,

Anderson³

et al. 1985

Neuroendocrinology

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“…Hojval et al [14] have reported, using nonequilibrium differential centrifugation, that IR-TSH is preferentially as sociated with a synaptosomally rich fraction in hypotha lamic homogenates. In the present study, we found that, when brought to equilibrium, the IR-TSH in hypothalamic homogenates was also associated with particles with a mo dal density greater than that reported for synaptosomes [10].…”

Section: Discussionmentioning

confidence: 99%

“…More importantly, hypothalamic tis sue from 21-day hypophysectomized rats, maintained in tis sue culture for 30 days, spontaneously releases IR-TSH into the culture medium (13]. In addition, potassium and veratri dine stimulate the release of IR-TSH from hypothalamic tissue by a calcium-dependent mechanism, while TRII is ineffective, and basal or potassium-stimulated hypothalam ic IR-TSH release is not affected by thyroid hormones [8], Finally, it has recently been demonstrated that IR-TSH is associated with a synaptosomal-rich fraction in the rat hy pothalamus [14], Taken together, these data indicate that IR-TSH is synthesized in the rat hypothalamus and stored in a releasable pool. To further assess the localization of IR-TSH in hypothalamic tissue, we examined the subcellu lar localization of IR-TSH in brain tissue using equilibrium density centrifugation.…”

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confidence: 99%

Subcellular Localization of Immunoreactive Thyroid-Stimulating Hormone in the Rat Hypothalamus

DeVito¹,

Spearman²,

Connors³

et al. 1986

Neuroendocrinology

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Hypothalamic tissue contains TSH-like material which is biologically, immunologically, and physicochemically similar to pituitary TSH. Immunoreactive thyroid-stimulating hormone (IR-TSH) is released from hypothalamic tissue in vitro by depolarizing concentrations of potassium or veratridine by a calcium-dependent mechanism. In the present study, we investigated the subcellular localization of IR-TSH using equilibrium density centrifugation. Tissue homogenates from intact, hypophysectomized or thyroidectomized rats were centrifuged at 150 g at 4°C for 10 min and the supernatants were layered onto continuous sucrose gradients (1.00–1.27 g/ml) and centrifuged at 100,000 g (max) for 16 h. IR-TSH in pituitary supernatants from intact and thyroidectomized rats showed high equilibrium density peaks with a modal density around 1.2 g/ml. Fractionation of the supernatant from ventral or dorsal hypothalamic homogenates resulted in abimodal distribution of IR-TSH. In supernatants from both tissues, IR-TSH containing particles were found at the top of the gradient in a low equilibrium density peak between 1.0 and 1.08 g/ml. In addition, IR-TSH containing particles were found in ventral and dorsal hypothalamic supernatants with modal densities at 1.16 and 1.25, respectively. These high density IR-TSH particles were present in tissue taken from hypophysectomized rats, and were not appreciably affected by thyroidectomy. Homogenization of the tissue in a hypo-osmotic medium disrupted the high density IR-TSH particles resulting in a single low density peak at the top of the gradient. These data suggest that hypothalamic IR-TSH is stored in membrane bound particles which have densities similar to that of secretory granules.

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