Demonstration of a Tonic Regulatory Thyrotropin Effect on Thyroid Function*

Friedman, Yochanan; Lang, Michael; Levasseur, Steven; Burke, Gerald

doi:10.1210/endo-104-2-467

Cited by 34 publications

(18 citation statements)

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“…The enzyme shares many features with PPs from other sources (see [ 151) including calf thyroid [7] in that it has multiple subcellular localizations and its activity in vitro is enhanced by Mg'+ and M.n'+ and inhibited by Co2+ and F-. The data presented here clearly show that thyroid PK activity (with and without CAMP) is elevated in the presence of high endogenous TSH ( fig.1) and depressed by TSH lack ( fig.2,3), thus confirming the findings [ 5,6]. What is of particular significance is the finding u* findings [21,22] that TSH induced the phosphorylation of histone suggests that our findings may have physiological significance.…”

Section: Discussionsupporting

confidence: 89%

Parallel regulation of cyclic amp‐dependent protein kinase and phosphoprotein phosphatase in rat thyroid

et al. 1979

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Section: Discussionsupporting

confidence: 89%

Parallel regulation of cyclic amp‐dependent protein kinase and phosphoprotein phosphatase in rat thyroid

et al. 1979

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“…After incubation for 10 min at 30"C, the reaction was terminated and the samples filtered as described [5].…”

Section: Protein Kinase Assaysmentioning

confidence: 99%

Differential effects of polyamines on rat thyroid protein kinase activities

Levasseur

Henricks

Poleck

et al. 1985

J of Cellular Biochemistry

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Ornithine decarboxylase, the rate-limiting enzyme in polyamine biosynthesis, has been shown to be regulated in thyroid by thyrotropin both in vivo and in vitro. Little, however, is known of the role of polyamines in thyroid cell function. Since studies in other tissues suggest that polyamines may influence protein phosphorylation, we studied the effect of the polyamines on various protein kinase activities in rat thyroid. Putrescine, spermidine, and spermine inhibit cyclic-AMP-dependent histone H1 kinase activity when measured in the cytosol fraction of rat thyroid; this effect is largely reproduced by NaCl concentrations of equivalent ionic strength. Both spermidine and spermine effect a 1.6-2.4-fold increase in cytosolic cyclic-AMP-independent (messenger-independent) casein kinase activity; stimulation by both polyamines is maximal at 5mM. A similar profile of stimulation is observed for messenger-independent casein kinase activity in crude nuclear preparations. Sodium chloride fails to stimulate both cytosolic and nuclear messenger-independent casein kinase activities at ionic strength equivalent to the spermine concentrations used. Spermine, but not putrescine, spermidine, or sodium chloride, inhibits calcium/phospholipid-dependent protein kinase C activity in cytosol extracts partially purified by DEAE chromatography. These findings suggest that regulation of protein kinase(s) by polyamines may represent a proximal locus (i) of action of thyrotropin-regulated ornithine decarboxylase activity in thyroid.

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“…Its effect being very brief, and taking place at very low concentrations of cAMP, may signify that this kinase is involved in the maintenance and regulation of the basal activity of some cellular processes. Indeed, in thyroid glands the 'tonic effect' of very low doses of TSH was reported [25]. It was found that the regulation of resting thyroid function by TSH apparently involves parallel changes in adenylate cyclase and protein kinase activities.…”

Section: Discussionmentioning

confidence: 99%

“…It was found that the regulation of resting thyroid function by TSH apparently involves parallel changes in adenylate cyclase and protein kinase activities. Therefore these enzymes may well be the primary loci for the observed tonic effect of TSH [25]. In addition, the necessity of the permanent presence of very low doses of TSH in thyroid cell culture system, for a good response to higher, stimulatory doses of TSH, has been reported [26].…”

Section: Discussionmentioning

confidence: 99%