cyclic-gmp and Hyperthyroidism

Topics: Animals; Bone Marrow Cells; Calcium; Cell Division; Cyclic AMP; Cyclic GMP; DNA; Female; Humans; Hyperthyroidism; Liver Regeneration; Male; Neoplasms; Rats; Thymus Gland

Topics: Chromatography, Ion Exchange; Cyclic AMP; Cyclic GMP; Diabetes Insipidus; Extracellular Space; Glucagon; Humans; Hyperthyroidism; Hypoparathyroidism; Hypothyroidism; Immune Sera; Inosine Nucleotides; Iodine Radioisotopes; Methods; Nucleotides, Cyclic; Phosphorus Radioisotopes; Protein Kinases; Tritium; Vasopressins

The role of C-type natriuretic peptide (CNP) in the pathophysiology of atrial function in hyperthyroidism has not been defined. This study was to define the role of CNP-activated particulate (p) guanylyl cyclase (GC)-cGMP-phosphodiesterase (PDE)3 signaling in the regulation of cAMP levels and contractile and secretory functions in the atria from hyperthyroid rabbits. Experiments were performed in perfused beating rabbit atria. CNP was used to activate pGC. In euthyroid atria from sham-treated rabbits, CNP (100 nM) increased cGMP and cAMP efflux by 176.7+/-17.7 and 55.3+/-10.0%, respectively. CNP decreased stroke volume and pulse pressure and ANP release by 51+/-7 and 41+/-2 and 60.4+/-3.2%, respectively. Pretreatment with milrinone blocked the CNP-induced increase of cAMP but without significant changes in decrease of atrial dynamics and ANP release. In hyperthyroid atria, CNP-induced increase of cGMP levels was accentuated, while CNP-induced increase of cAMP was attenuated. The gain of cAMP, i.e., change in cAMP efflux concentration in terms of cGMP was attenuated in the hyperthyroid compared to euthyroid atria. CNP rather increased atrial dynamics in hyperthyroid atria instead of decrease. CNP-induced decrease in atrial ANP release was attenuated. Pretreatment with milrinone blocked the CNP-induced increase of cAMP levels concomitantly with a decrease of atrial dynamics. The present study demonstrates that altered role of CNP-activated pGC-cGMP-PDE3-cAMP signaling is involved in the pathophysiology of hyperthyroid heart.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Atrial Natriuretic Factor; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 3; Enzyme Activation; Guanylate Cyclase; Heart Atria; Hyperthyroidism; In Vitro Techniques; Myocardium; Natriuretic Peptide, C-Type; Rabbits; Signal Transduction

Thyroid disease has profound effects on cardiovascular function. Hypo- and hyperthyroidism, for example, are associated with reduced and increased maximal endothelium-dependent vasodilation respectively. We therefore hypothesized that the capacity for vascular nitric oxide (NO) formation is decreased in hypothyroidism and increased in hyperthyroidism. To test this hypothesis, rats were made hypothyroid (HYPO) with propylthiouracil or hyperthyroid (HYPER) with triiodothyronine over 3-4 months. Compared with euthyroid control rats (EUT), HYPO exhibited blunted growth and lower citrate synthase activity in the soleus muscle; HYPER exhibited left ventricular hypertrophy and higher citrate synthase activity in the soleus muscle (P<0.05 for all effects). The capacity for NO formation was determined in aortic extracts by formation of [3H]L-citrulline from [3H]L-arginine, i.e. NO synthase (NOS) activity. Thyroid status modulated NOS activity (EUT, 36.8 +/- 5.5 fmol/h per mg protein; HYPO, 26.0 +/- 7.9; HYPER, 64.6 +/- 12.7; P<0.05, HYPER vs HYPO). Expression of endothelial and neural isoforms of NOS was modulated by thyroid status in a parallel fashion. Capacity for responding to NO was also determined via measuring cGMP concentration in aortae incubated with sodium nitroprusside. Stimulated cGMP formation was also modulated by thyroid status (EUT, 73.0 +/- 20.2 pmol/mg protein; HYPO, 152.4 +/- 48.7; HYPER, 10.4 +/- 2.6; P<0.05, HYPER vs HYPO). These data indicate that thyroid status alters capacities for both formation of and responding to NO. The former finding may contribute to previous findings concerning vascular function in thyroid disease states.

Topics: Animals; Aorta; Citrate (si)-Synthase; Cyclic GMP; Endothelium, Vascular; Hyperthyroidism; Hypothyroidism; Immunohistochemistry; Male; Muscle, Skeletal; Nitric Oxide; Nitric Oxide Synthase; Nitroprusside; Rats; Rats, Sprague-Dawley; Thyroid Diseases; Vasodilator Agents

The significance of PDE2 on the atrial inotropy was studied in eu- and hyperthyroidism. The contractile force was measured and negative inotropic capacity of N6-cyclopentyladenosine (CPA) was determined on left atria isolated from 8-day thyroxine- or solvent-treated guinea pigs, in the presence or absence of EHNA (adenosine deaminase and PDE2 inhibitor) or NBTI (nucleoside transporter inhibitor). EHNA was administered to inhibit PDE2, while NBTI was used to model the accumulation of endogenous adenosine. The reduction of the contractile force caused by EHNA was smaller in the thyroxine-treated atria than in the solvent-treated samples. Contrary, NBTI induced a decrease in the contractile force without significant difference between the two groups. In addition, EHNA enhanced the efficiency of CPA in thyroxine-treated atria and did not affect it in solvent-treated samples, while the response to CPA was decreased by NBTI in all atria, especially in hyperthyroidism. On the basis of greater retention of the contractile force and sustained/enhanced responsiveness to CPA in the presence of EHNA we conclude that PDE2's inhibition has a significant positive inotropic effect in guinea pig atria and this effect is proven to be augmented in hyperthyroidism.

Topics: Adenine; Adenosine; Animals; Cardiotonic Agents; Culture Techniques; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 2; Guinea Pigs; Heart Atria; Hyperthyroidism; Male; Myocardial Contraction; Phosphoric Diester Hydrolases; Thioinosine

Hyper- and hypothyroid states occasionally induce skeletal muscle dysfunction i.e. periodic paralysis and thyroid myopathy. The etiology of these diseases remains unclear, but several findings suggest that the catecholamine-beta-receptor-cAMP system or other messenger systems are disturbed in these diseases. In this context, we evaluated changes in the cyclic 3',5'-nucleotide metabolic enzyme, cyclic 3',5'-nucleotide phosphodiesterase (PDE) and calmodulin concentrations in skeletal muscles of hyper- and hypothyroid rats. Activities of cyclic AMP-PDE were low in skeletal muscle both from hyper- and hypothyroid rats, and calmodulin concentration was high in hyperthyroid and low in hypothyroid rats, as compared with normal rats. DE-52 column chromatographic analysis showed that the cGMP hydrolytic activity in peak I and the cAMP hydrolytic activity in peak II were decreased in hypothyroid rats, whereas cAMP hydrolytic activity in peak III was unchanged. The cAMP hydrolytic activity in peak III was decreased in hyperthyroid rats, but the activities in peaks I and II were unchanged. These findings indicate that cAMP and calmodulin may have some role in skeletal muscle function in the hyperthyroid state, and that cAMP and calmodulin-dependent metabolism may be suppressed in the hypothyroid state.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Calmodulin; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 1; Hydrolysis; Hyperthyroidism; Hypothyroidism; Male; Muscle, Skeletal; Rats; Rats, Wistar; Thyroid Diseases

The aim of the study was to answer the question whether a rapid decrease in serum triiodothyronine (T3) and thyroxine (T4) levels resulting from the treatment with a full dose (3 x 20 mg daily) of methimazole applied in patients with thyrotoxicosis is associated with the parallel diminution of plasma atrial natriuretic peptide (ANP) and its second messenger-cyclic guanosine monophosphate (cGMP) concentrations. Sixteen patients with thyrotoxicosis of mean age 41.5 +/- 10.5 years participated in the study. Short-term (10 days) methimazole treatment resulted in a significant decrease in serum T3 and T4 concentrations to the values found in 14 healthy subjects serving as control group. Plasma ANP and cGMP levels also decreased significantly during the treatment attaining the normal range. A significant correlation was found between the decrease in serum T3 and T4 concentrations during the treatment and the decrease in plasma ANP level. The decrease in plasma ANP was not closely correlated with the reduction of cGMP levels. These results indicate that: 1) a steep decrease in serum thyroid hormone concentrations induced by a full methimazole treatment during ten days in patients with thyrotoxicosis due to Graves' disease was accompanied by the return of elevated plasma ANP levels to normal range; 2. diminution of serum concentrations of both T3 and T4 during the treatment was correlated with the decrease in plasma ANP; 3) reduction in plasma cGMP concentration associated with short-term methimazole treatment in thyrotoxicosis seems to depend not only on the diminution of plasma ANP level.

Topics: Adult; Atrial Natriuretic Factor; Cyclic GMP; Female; Humans; Hyperthyroidism; Male; Methimazole; Middle Aged; Thyroxine; Triiodothyronine

We investigated the role of endothelium derived relaxing factor (EDRF) and cyclic guanosine monophosphate (cGMP) in the altered vascular reactivity of hyperthyroidism (HT). Rats were given daily injections of triiodothyronine (T3), 50 micrograms/100 g body weight for two weeks, and they had significantly higher serum levels of T3 compared to untreated, control rats (493 +/- 82 vs. 58 +/- 7 ng/dl, p less than 0.05) and significant elevations in their systolic blood pressure (188 +/- 6 vs 126 +/- 3 mm Hg, p less than 0.05). Vascular reactivity was studied in isolated muscle baths; cGMP was measured by RIA. There were no differences in contractile responses to phenylephrine (PE) in isolated aortae from the HT and control rats, but aortae from the HT rats contracted with PE relaxed less to acetylcholine (Ach); the calcium ionophore, A23187; and sodium nitroprusside (SNP). Sensitivity to atrial natriuretic factor (ANF) and 8-Br cGMP was unaltered. Blood vessels from HT rats generated significantly less cGMP in response to Ach, SNP, and ANF. Treatment of the hypertension in the HT rats which hydralazine or propranolol restored the vascular relaxation response to Ach but not SNP; cGMP responses remained blunted. These data suggest that endothelium dependent vasodilators may induce relaxation independent of elevations of cGMP in aortae from HT rats.

Topics: Acetylcholine; Animals; Biological Products; Cyclic GMP; Hydralazine; Hypertension; Hyperthyroidism; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Nitric Oxide; Nitroprusside; Phenylephrine; Rats; Rats, Inbred Strains; Vasodilation

We measured plasma atrial natriuretic peptide (ANP) levels in 17 patients with newly diagnosed thyrotoxicosis. ANP was elevated compared to a group of healthy controls and fell to normal after treatment. Plasma cyclic guanosine monophosphate was also raised in untreated patients. Elevated circulating levels of ANP may play a part in the haemodynamic changes of hyperthyroidism.

Topics: Adult; Atrial Natriuretic Factor; Carbimazole; Cyclic GMP; Humans; Hyperthyroidism; Middle Aged; Propylthiouracil; Thyrotoxicosis

Previous observations that cyclic 3',5'-nucleotide phosphodiesterase activity exists in mammalian sera including human serum prompted us to investigate the phosphodiesterase levels in sera of patients with various thyroid disorders. Both serum cyclic AMP phosphodiesterase (cAMP-PDE) and cyclic GMP phosphodiesterase (cGMP-PDE) activities measured in a low substrate concentration were elevated 3-fold in subacute thyroiditis and slightly in hyperthyroidism, compared to the normal. Slight decreases of these enzyme activities were observed in primary hypothyroidism. PDE activities were positively correlated with the value of T3-RSU and serum thyroid hormone levels in hyper- and hypothyroidism. Altered enzyme activities returned to normal during the course of recovery. Identical results were obtained when plasma was tested. These results suggest that serum PDE activities may be partly related to the thyroid function.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Cyclic AMP; Cyclic GMP; Humans; Hyperthyroidism; Hypothyroidism; Thyroid Diseases; Thyroid Neoplasms

Topics: Adolescent; Adult; Aged; Cyclic AMP; Cyclic GMP; Female; Humans; Hyperthyroidism; Hypothyroidism; Male; Middle Aged

Plasma levels and 24-h urinary excretion of cyclic AMP and cyclic GMP were measured in 18 patients with hyperthyroidism, 7 patients with hypothyroidism and 25 normal subjects. Mean plasma and urinary levels of both cyclic AMP and cyclic GMP were significantly positive correlations between the serum thyroid hormone levels and plasma and urinary cyclic nucleotide concentrations were also found, suggesting that the elevated extracellular cyclic nucleotide levels in hyperthyroidism are probably a consequence of increased secretion of thyroid hormones. In the hypothyroid patients the extracellular cyclic nucleotide concentrations did not differ significantly from those of the normal subjects.

Topics: Adolescent; Adult; Aged; Cyclic AMP; Cyclic GMP; Female; Humans; Hyperthyroidism; Hypothyroidism; Male; Middle Aged; Thyroid Hormones

Topics: Animals; Cyclic AMP; Cyclic GMP; Endocrine Glands; Guanylate Cyclase; Humans; Hyperthyroidism

The effect of insulin-induced hypoglycaemia and methacholine on plasma cAMP and cGMP levels was studied in normal volunteers, hyperthyroid and hypothyroid patients. A significant positive correlation existed between the maximal increase in plasma cAMP and the maximal decrease in plasma glucose in normals during insulin-induced hypoglycaemia. Therefore, the plasma cAMP response is considered to be dependent on the degree of hypoglycaemia, rather than the dose of insulin. The cAMP response to hypoglycaemia was significantly higher in hyperthyroid patient, and was lower in patients with hypothyroidism than in normals. The cAMP response of the hyperthyroid patients was normalized when their hyperthyroidism was controlled after 3 months of treatment. The plasma level of cGMP was slightly elevated during hypoglycaemia, but there was no significant difference between controls and hyperthyroid patients. The cGMP response to methacholine, which is probably mediated by cholinergic receptors, was significantly potentiated in hyperthyroid patients. The cAMP response, which is presumably dependent on endogenous catecholamines secreted during methacholine-induced hypotension, was also enhanced in hyperthyroid patients. It is likely that beta-adrenergic receptor responses and cholinergic receptor responses are both enhanced in hyperthyroidism.

Topics: Adolescent; Adult; Blood Glucose; Catecholamines; Cyclic AMP; Cyclic GMP; Female; Humans; Hyperthyroidism; Hypothyroidism; Insulin; Male; Methacholine Compounds; Middle Aged; Receptors, Adrenergic, beta

Modifications in characteristics and activities of beta-adrenergic receptors and certain parameters of the cyclic nucleotide systems were observed in the hypertrophied heart of the rat chronically treated with T4. These include: 1) an increased number of beta-adrenergic receptors without a change in their affinity, as determined by binding of (-)-[3H]dihydroalprenolol to the membrane; 2) increased sensitivity and magnitude of stimulation of adenylate cyclase in homogenates by isoproterenol, without a change in the basal or NaF-stimulated (total) enzyme activity; 3) decreased formation of cAMP and decreased activation of cAMP-dependent protein kinase in the minced heart stimulated by isoproterenol, probably due to decreased myocardial ATP concentration; 4) decreased activity of cAMP phosphodiesterase in the particulate fraction; 5) decreased activity of cGMP-dependent protein kinase in both the soluble and particulate fractions, accompanied by decreased activity of cAMP-dependent protein kinase in the particulate fraction; 6) decreased activity of the stimulatory modulator of cGMP-dependent protein kinase and, conversely, increased activity of the inhibitory modulator of cAMP-dependent protein kinase; and 7) increased sensitivity accompanied by decreased maximum tension development of the ventricular strip to contract in response to isoproterenol. These alterations largely disappeared upon regression of the hyperthyroid state. It is suggested that the above changes, many of which were the opposite of those reported earlier for the desensitized and hypertrophied rat heart caused by isoproterenol, may in part consitute the molecular basis for the reputed catecholamine supersensitivity of the heart in the hyperthyroid state.

Topics: Adenylyl Cyclases; Animals; Cardiomegaly; Cyclic AMP; Cyclic GMP; Dihydroalprenolol; Fluorides; Heart; Hyperthyroidism; Isoproterenol; Kinetics; Male; Myocardium; Rats; Receptors, Adrenergic; Receptors, Adrenergic, beta; Thyroxine

Topics: Acetylcholine; Animals; Blood Pressure; Catecholamines; Cyclic AMP; Cyclic GMP; Epinephrine; Humans; Hyperthyroidism; Hypothyroidism; Insulin; Isoproterenol; Physical Exertion; Propranolol; Rats; Stress, Physiological; Tyramine

Plasma cyclic AMP and cyclic GMP levels were studied in a group of normal subjects and 10 subjects with hyperthyroidism. In the control group, mean plasma cyclic AMP levels were 15.3 +/- 1.3 nmol/l (SEM), and plasma cyclic GMP levels were 9.4 +/- 0.58 nmol/l (SEM). In untreated hyperthyroid subjects, both plasma cyclic AMP and cyclic GMP levels were significantly elevated above normal with mean values of 35.0 +/- 2.4 nmol/l (SEM) (P less than 0.001) and 14.7 +/- 0.2 nmol/l (SEM), (P less than 0.001), respectively. Six of the hyperthyroid subjects were re-studied when they became euthyroid; plasma cyclic nucleotide concentrations all fell within the normal range. To evaluate the relative contribution of triiodothyronine and thyroxine to elevated plasma cyclic nucleotide levels, two hyperthyroid subjects were treated with propylthiouracil and iodide. Plasma cyclic nucleotide levels were normalized when plasma triiodothyronine levels declined to normal range, at the time when plasma thyroxine levels were still elevated. These preliminary data suggest that increased triiodothyronine production is responsible for the increased cyclic nucleotide levels in hyperthyroidism.

Topics: Adult; Aged; Cyclic AMP; Cyclic GMP; Humans; Hyperthyroidism; Male; Middle Aged; Potassium Iodide; Propylthiouracil; Thyroxine; Triiodothyronine

The plasma c-AMP level increases significantly in response to pharmacologica doses (1 mg i. v.) of glucaton. Beta blocking agents somewhat inhibit this increase in both euthyroid and hyperthyroid subjects. Catecholamine release elicited by glucagon thus plays some part in the response. In euthyroid subjects 2 microgram/kg glucagon still produces a significant increase in the plasma c-AMP concentration and propranolol fails to counteract this response. The c-AMP response elicited by identical doses of glucagon is more marked in hyperthyroid than in euthyroid subjects and can be somewhat reduced by propranolol. This indicates that in hyperthyroid patients even low doses of glucagon stimulate the release of catecholamines or enhance the responsiveness of beta receptors. The plasma c-GMP level increases in response to glucagon loading but in a lesser degree than does the c-AMP concentration. The response of c-GMP to glucagon is more protracted than the response of c-AMP and propranolol fails to counteract it.

Topics: Adult; Cyclic AMP; Cyclic GMP; Female; Glucagon; Humans; Hyperthyroidism; Middle Aged; Propranolol

Cyclic AMP and cyclic GMP phosphodiesterase activities (3',5'-cyclic AMP 5'-nucleotidohydrolase, EC 3.1.4.17) were investigated in the human thyroid gland from patients with hyperthyroidism. Low substrate concentration (0.4 muM) was used. About 60% of the cyclic-AMP and 80% of the cyclic-GMP hydrolytic activities in the homogenate were obtained in the soluble fraction (105 000 X g supernatant). The thyroid gland contains two forms of cyclic-AMP phosphodiesterase, one with a Km of 1.3-10(-5) M and the second with a Km of 2-10(-6) M. Cyclic-AMP and cyclic-GMP phosphodiesterase were purified by gel filtration on a Sepharose-6B column. Cyclic-AMP phosphodiesterase activities were found in a broad area corresponding to molecular weights ranging from approx. 200 000 to 250 000 and cyclic-GMP phosphodiesterase activity was found in a single area corresponding to a molecular weight of 260 000. Cyclis-AMP phosphodiesterase activities were stimulated by the protein activator which was found in human thyroid and this stimulation was dependent on Ca2+. Stimulation of cyclic-AMP phosphodiesterase by the activator was not significant even in the presence of enough Ca2+. The effect of D,L-triiodothyronine, D,L-thyroxine, L-diiodotyrosine, L-monoiodotyrosine, L-thyronine, L-diiodothyronine, thyrotropin, hydrocortisone, adrenocorticotropin, cyclic-AMP and cyclic-GMP on the phosphodiesterase activities was studied. Cyclic-AMP, cyclic-GMP, D,L-triiosothyronine, D,L-thyroxine, adrenocorticotropin and hydrocortisone where found to inhibit the phophodiesterase. Triiodothyronine and thyroxine inhibited cyclic-AMP phosphodiesterase more effectively than cyclic-GMP phosphodiesterase. Thyroxine was a more potent inhibitor than triiodothyronine. The concentration of cyclic AMP producing a 50% inhibition of cyclic-GMP phosphodiesterase activity was 5-10(-5) M, while the concentration of cyclic GMP producing a 50% inhibition of cyclic-AMP phosphodiesterase was 3-10(-3) M. Both cyclic-AMP and cyclic-GMP phosphodiesterase activities in the homogenate of hyperthyroidism, thyroid carcinoma and adenoma were higher than in normal thyroid tissue, when assayed with a low concentration of the substrate (0.4 muM). When a higher concentration (1 mM) of cyclic nucleotides was used as the substrate, cyclic-AMP hydrolytic activity in adenoma tissue was similar to that of normal tissue, while the other activities were higher than normal.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Adenoma; Calcium; Carcinoma; Cyclic AMP; Cyclic GMP; Enzyme Activation; Hormones; Humans; Hyperthyroidism; Kinetics; Phosphoric Diester Hydrolases; Subcellular Fractions; Thyroid Gland; Thyroid Neoplasms; Thyroxine; Triiodothyronine

Urinary cyclic AMP, cyclic GMP and creatinine excretion were measured in 38 patients with hyperthyroidism, 32 patients with hypothyroidism and in 57 normal subjects. The excretion of both cyclic nucleotides was significantly increased in hyperthyroid females, but not in hyperthyroid males. The cyclic nucleotides/creatinine ratios, however, were uniformly elevated in both male and female hyperthyroid subjects and this was due, in part, to decreased creatinine excretion. Cyclic AMP excretion was significantly decreased in the hypothyroid subjects, but the cyclic AMP/creatinine ratios were not significantly different from normal. There were no significant alterations in cyclic GMP and cyclic GMP/creatinine ratios in the male hypothyroid patients, but ratios in the female patients were slightly greater than in the normals. These results demonstrate that hyper- and hypothyroidism may be associated with appreciable alterations in urinary cyclic nucleotide levels and that there may be sex-related differences in the patterns of urinary excretion of these nucleotides. The cyclic nucleotide levels herein described in patients with hyper- and hypothyroidism are qualitatively and, in some instances, quantitatively similar to those found in patients with hyper- and hypoparathyroidism, respectively.

Topics: Creatinine; Cyclic AMP; Cyclic GMP; Female; Humans; Hyperthyroidism; Hypothyroidism; Male; Sex Factors