Vascular relaxation, aging and thyroid hormones

Parker, Robert; Berkowitz, Barry A.; Lee, Chi-ho; Denckla, W D

doi:10.1016/0047-6374(78)90038-6

Cited by 25 publications

(12 citation statements)

References 7 publications

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“…Because of the similarities between the symptoms of senescence and those of hypothyroidism, a link between the aging process and changes in thyroid function has frequently been suggested (refer Cole et al, 1982). From the study, referred to in the Introduction, which explored this concept (Parker et al, 1978) it cannot be deduced whether thyroid hormone treatment specifically reversed the effects of aging on vascular responses to isoprenaline, or whether it produced an effect that was opposite to, but separate from, the effect of aging on isoprenaline responses. The data obtained in the present study provide evidence that thyroid hormone treatment of aged rats did not simply reverse the effects of aging on vascular P-adrenoceptor-mediated responses.…”

Section: Discussionmentioning

confidence: 99%

“…Thirdly, although the reason why aging is accom-panied by a reduction in P-adrenoceptor-mediated vascular relaxation is not known (Fleisch, 1981), Parker et al (1978) suggested that it might be due to an age-related loss in the responsiveness of the blood vessels to thyroid hormones. They observed that the relaxant responses of rat isolated aorta to isoprenaline were reduced not only in preparations from aged rats but also in preparations from thyroidectomized rats.…”

Section: Introductionmentioning

confidence: 99%

“…The isolated blood vessel preparations used throughout the present study were from rat aorta (because this preparation was used in the study carried out by Parker et al, 1978), or from rat pulmonary artery (because this vessel was used in our previous studies on aging, O'Donnell & Wanstall, 1984a).…”

Section: Introductionmentioning

confidence: 99%

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Thyroxine treatment of aged or young rats demonstrates that vascular responses mediated by β‐adrenoceptor subtypes can be differentially regulated

O’Donnell

Wanstall

1986

British J Pharmacology

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1 Responses to vascular relaxant drugs were obtained on KCI (15 mM)-contracted isolated ring preparations ofpulmonary artery and aorta from young (1-2 months old) and aged (> 16 months old) rats. These vessels contain both PI-and P2-adrenoceptors.2 Relaxant responses (i.e. relaxation expressed as a % of the KCI-induced contraction) to isoprenaline, procaterol (02-selective partial agonist), fenoterol (02-selective) and noradrenaline (filselective) but not those to forskolin, 3-isobutyl-l-methylxanthine, enprofylline or sodium nitrite, were smaller on preparations from aged rats than on those from young rats. 3 Thyroxine (T4)-treatment (1 mg kg-' s.c. thrice weekly for 3-5 weeks) of aged or young rats enhanced responses to isoprenaline and noradrenaline but reduced those to procaterol, when compared with preparations from age-matched saline-treated control rats. 4 The agonist order of potency, determined in young rats, was isoprenaline>noradrenaline>adre-naline in preparations from T4-treated rats compared with isoprenaline > adrenaline > noradrenaline in saline-treated control rats.5 It is concluded (a) that the age-related decline in vascular responses to P-adrenoceptor agonists involves P-adrenoceptor mechanisms specifically and possibly P2-adrenoceptors more than PIadrenoceptors; and (b) that T4-treatment of rats enhances Pi-adrenoceptor-mediated and reduces, or does not change, P2-adrenoceptor-mediated responses of preparations of rat pulmonary artery and aorta. In preparations from control rats V2-adrenoceptors were functionally predominant but in preparations from T4-treated rats Pl-adrenoceptors appeared to become functionally predominant.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thyroxine treatment of aged or young rats demonstrates that vascular responses mediated by β‐adrenoceptor subtypes can be differentially regulated

O’Donnell

Wanstall

1986

British J Pharmacology

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“…Since mame rats are less responsive to thyroid hormones than younger rats (Parker et d. 1978), and since it was our objective to temporally characterize a maximal response to T%j replacement, we intentionally chose a high replacement dose.…”

Section: Rpl Vs Veh Interactionmentioning

confidence: 99%

Hypothyroidism increases serotonin turnover and sympathetic activity in the adult rat

Henley¹,

Chen²,

Klettner³

et al. 1991

Can. J. Physiol. Pharmacol.

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Adult, male Sprague-Dawley rats underwent surgical thyroidectomy (Tx) or sham surgery. In all three experiments from which data are reported, a 3-week recovery period was allowed. In experiments I and II, baseline measurements of colonic temperature (Tc) and urinary norepinephrine excretion (NE) were obtained, and both variables were monitored daily for the duration of the studies. After baseline measurements, half of each surgical group was given either triiodothyronine (T3) or vehicle injections subcutaneously; in experiment I replacements continued for 1.5 days, while in experiment II T3 replacement continued for 3.5 days. Rats were decapitated at the end of each experiment and serotonin (5-HT) turnover was measured in brainstem. Serotonin turnover in rostral and caudal brainstem was increased with Tx (p less than 0.05). Increased turnover in caudal brainstem was normalized by T3 only in experiment II. Similarly, decreased Tc and elevated NE with Tx were normalized in experiment II but not in experiment I. In experiment III, NE measurements normalized on a creatinine excretion basis indicated that increased NE is evident with Tx, irrespective of normalization procedure. Significant correlations between 5-HT in caudal brainstem and metabolic correlates of sympathetic function, concurrent normalization of NE and 5-HT in caudal brainstem, plus work from other laboratories describing sympathoexcitatory serotonergic neurons located in the caudal brainstem suggest that the central and peripheral changes in the hypothyroid rat are causally related.

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“…Also, similar findings of a loss in responsive ness of blood vessels to beta-adrenoceptor agonists have been reported by several investigators (7)(8)(9). As one of the important factors that could underlie age-related al terations in beta-adrenoceptor responsive ness of the cardiovascular system, much attention has been given to thyroid hormone (10,11). We have recently observed that exogenous administration of thyroid hormone (T3) partially restored these age-related decreases in beta-adrenoceptor activity of the cardiovascular system (12), suggesting that the effects of thyroid hormone and age related alterations of cardiovascular responsi veness to beta-adrenoceptor stimulation are interrelated.…”

mentioning

confidence: 99%

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

Tsujimoto

Hashimoto

1987

Jpn.J.Pharmacol

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Abstract-We have compared the vasopressor response of alpha-adrenoceptor agonists in young (2 month-old) and older (12 month-old) pithed rats both in the presence and absence of triiodo-L-thyronine (T3)-induced hyperthyroidism. There was no age-related changes in the pressor response to either the alpha, selective agonist phenylephrine or the alpha2-selective agonists clonidine and UK 14,304. However, T3-induced hyperthyroidism caused a selective reduction in postjunctional alpha2-adrenoceptor-mediated pressor responses but not alpha, adrenoceptor-mediated ones in both age groups. In contrast to vascular alpha adrenoceptors, there was an age-related decrease in the number of myocardial alpha, -adrenoceptor sites measured by specific binding of [3H] prazosin. With thyroid hormone treatment, the density of ventricular alpha, receptors was found to be further reduced even in the older rats. These results suggest that thyroid hormone and aging have different influences on the cardiovascular alpha-adre noceptor system and that these two physiological variables are independently

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Vascular relaxation, aging and thyroid hormones

Cited by 25 publications

References 7 publications

Thyroxine treatment of aged or young rats demonstrates that vascular responses mediated by β‐adrenoceptor subtypes can be differentially regulated

Thyroxine treatment of aged or young rats demonstrates that vascular responses mediated by β‐adrenoceptor subtypes can be differentially regulated

Hypothyroidism increases serotonin turnover and sympathetic activity in the adult rat

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

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