Activation of protein kinase in thyroid slices by thyroid-stimulating hormone.

The present investigation describes experimental conditions under which histamine stimulates cAMP-dependent protein kinase in the guinea-pig stomach. A histamine-responsive cAMP-dependent protein kinase was shown to be present in the soluble fraction obtained after a low speed centrifugation of the stomach homogenate. There was a small, but detectable stimulation of protein kinase activity and cAMP formation when tissue was incubated with histamine. This response to histamine was highly pronounced in the presence of a phosphodiesterase inhibitor. Protein kinase activation was assessed by measuring protein kinase activity ratio (activity -cAMP/+cAMP). Results indicate that protein kinase activity ratios reflect cAMP tissue levels. Binding of free cAMP by charcoal lowered both cAMP levels and protein kinase activity ratio, but histamine activation was still evident. Results suggest that only a portion of intracellular cAMP, probably in a bound form, is actually responsible for protein kinase activation, and the large accumulation of cAMP in the presence of a phosphodiesterase inhibitor probably does not reflect physiological levels.

show abstract

Thyrotropin-induced increase in phosphoprotamine phosphatase activity in rat thyroid

Roques

Tirard

Rapaud

1980

J Endocrinol Invest

View full text Add to dashboard Cite

Phosphoprotamine phosphatase activity in the rat thyroid was examined by studying the release of inorganic phosphate from [32P]-phosphorylated protamine. Rats were given a normal diet supplemented or not with thyroxine (T4) (3 mg/l in 0.05% bovine serum albumin solution) or propylthiouracil (1 g/l in 1% sucrose solution) in drinking water for various periods. TSH was injected ip, 100 mU per animal. A significant increase of phosphatase specific activity-units per mg protein (3-fold) as well as units per gland- was observed following goitrogen treatment, whereas a decrease (50%) was seen in response to T4. Both the soluble and particle activities were similarly affected. As total activity decreased after T4 treatment, it appeared that only the Mn2+-stimulating enzyme was concerned, the Mn2+-unstimulated part remaining unaltered. In vitro cyclic AMP or cyclic GMP at concentrations from 10 micro M to 200 micro M had no effect on these phosphatase activities. TSH injected in chronically T4-treated rats (32 days treatment) failed to produce any significant enhancement in phosphatase activity whatever the time of injection before sacrifice (from 2 to 6 h). On the contrary a single injection of TSH in animals subjected to short treatment with T4 (2 days) induced an elevation of the enzyme activity, restoring partially the initial level. These findings suggest that TSH controls protein dephosphorylation activities in the thyroid. Furthermore, they offer additional evidence that prolonged T4 administration leads to decreased responsiveness to TSH.

show abstract

Activation of protein kinase in thyroid slices by thyroid-stimulating hormone.

Cited by 37 publications

References 28 publications

The Role of Cyclic Nucleotides in the Thyroid Gland

The Role of Cyclic Nucleotides in the Thyroid Gland

Regulation by histamine of cAMP-dependent protein kinase in guinea-pig stomach

Thyrotropin-induced increase in phosphoprotamine phosphatase activity in rat thyroid

Contact Info

Product

Resources

About