The EFFECT OF AGING ON Α‐ADRENOCEPTORS AND THEIR RESPONSES IN RABBITS

Hamilton, Carlene A.; Dalrymple, H. W.; Jones, C. R.; Reid, JL

doi:10.1111/j.1440-1681.1985.tb00906.x

Cited by 8 publications

(4 citation statements)

References 38 publications

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“…20 Interestingly, other animal studies also indicate that the a1-receptor density seems to decrease with increasing age, attenuating the responsiveness to a1-adrenergic agonists. [33][34][35][36] This is supported by a human study, in which infusion of the a1-adrenergic receptor agonist, phenylephrine, in young (mean age: 25.1 years) and old (mean age: 72.2 years) subjects at rest caused a less pronounced vasoconstriction response in the leg arteries of the older subjects. 37 Therefore, a higher a1-adrenergic receptor density would render peripheral arteries more sensitive to serum calcium.…”

Section: Discussionmentioning

confidence: 97%

Serum calcium revisited: associations with 24-h ambulatory blood pressure and cardiovascular reactivity in Africans

et al. 2010

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Sub-Saharan Africans face an increasing burden of hypertension. Although controversial, recent experimental evidence strongly suggests that serum calcium contributes to elevated blood pressure through increased vascular resistance. We investigated the associations of 24-h blood pressure and cardiovascular reactivity with serum calcium in African men stratified by age. The study consisted of 50 younger (median age: 38 years) and 49 older (median age: 49 years) participants. We measured 24-h ambulatory blood pressure with a mean successful inflation rate of 72.6%. Total peripheral resistance and stroke volume reactivity were obtained using a Finometer device during application of the Stroop color and word conflict test. Total serum calcium was adjusted for serum albumin. Results showed that serum calcium levels were similar between the younger and older groups. However, in the younger group, 24-h systolic blood pressure, 24-h diastolic blood pressure and total peripheral resistance reactivity correlated positively, whereas stroke volume reactivity correlated negatively with serum calcium in single and multiple regression analyses (systolic blood pressure: B¼34.99, P¼0.017; diastolic blood pressure: B¼34.93, Po0.001; total peripheral resistance reactivity: B¼65.44, P¼0.048; stroke volume reactivity: B¼À45.40, P¼0.017). No associations were evident in the older African men. In conclusion, 24-h ambulatory systolic and diastolic blood pressures are positively associated with serum calcium in African men younger than 43 years. The blood pressure-serum calcium relationship seems to be mediated through increased vascular resistance during stress.

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Section: Discussionmentioning

confidence: 97%

Serum calcium revisited: associations with 24-h ambulatory blood pressure and cardiovascular reactivity in Africans

et al. 2010

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“…Several studies have demonstrated that vascular reactivity varies dramatically with postnatal developmental age. This observation holds for a variety of vascular beds, including cerebral (19,40,41), renal (18,28), femoral (36), and pulmonary (14,15,42) circulations. These data have been obtained in various species such as sheep (1,41), rat (12), pig (36,42), dog (37), rabbit (14,18), baboon (19,20), and human (5).…”

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confidence: 81%

Development of fetal vascular responses to endothelin-1 and acetylcholine in the sheep

Docherty

Kalmar-Nagy

Engelen

et al. 2001

American Journal of Physiology-Regulatory, Integrative and Comp

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Responses to K(+), endothelin-1 (ET-1), and acetylcholine (ACh) of isolated adrenal, femoral, middle cerebral, and renal arteries from fetal [110--145 days gestational age (dGA, term approximately 148 dGA)] and 0- to 24-h newborn (NB) lambs were evaluated using the technique of wire myography. Responses at distinct developmental ages for each vascular bed were compared. In all arteries sensitivity to K(+)-induced vasoconstriction was similar at all fetal age points examined. In contrast, sensitivity to ET-1 increased with increasing fetal age in arteries from all vascular beds. The magnitude of the maximal vasoconstriction was positively correlated with GA for K(+) in adrenal, femoral, and cerebral arteries and for ET-1 in femoral, cerebral, and renal arteries. Cerebral arteries showed a greater sensitivity when compared with the other systemic arteries to K(+) and ET-1 at all fetal ages and to K(+) in NB. ACh evoked relaxatory responses in fetal and NB femoral and adrenal arteries. However, renal arteries relaxed comparatively less in response to ACh, and no vasodilation was noted in middle cerebral arteries at any age points examined. For femoral arteries ACh-induced vasorelaxation decreased with increasing GA but was restored in arteries from NB lambs. In summary, the responsiveness of isolated resistance arteries varies with developmental age in the fetal and perinatal sheep and these effects are both agonist and vascular bed specific. The augmented sensitivity in response to ET-1 of middle cerebral compared with other systemic arteries may reflect the importance of cerebral blood flow control during this critical developmental period.

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“…However, they found no direct relation between the number of receptors and functional changes. 404 The reasons for the changes are not known but may be related to changes in hormone levels which occur before the animal reaches maturity. Alpha2-adrenoceptors labelled by [3H]clonidine have also been observed to decrease with age in the rabbit brain.402 However a decreased number of alpha,-adrenoceptors on platelets in newborn human infants has been reported and correlated with a diminished response of newborn platelets to adrenalinee405…”

Section: F Regulation Of Alpha-adrenoceptorsmentioning

confidence: 97%