Catecholamines, derived from the amino acid tyrosine, produced by
the adrenal glands, which are found on top of the kidneys. are
epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine.
The hormone are released into the blood during times of physical or
emotional stress.
A. Epinephrine
9. Catecholamine-releasing action in guinea-pig papillary muscles
In the study to investigate wheather tetraethylammonium ion (TEA)
prolongs the action potential (AP) was examined by standard
microelectrode techniques in papillary muscles
isolated from nonreserpinized and reserpinized guinea-pig hearts,
showed that TEA modifies its intrinsic prolonging action of the AP by
releasing norepinephrine from sympathetic nerve terminals; TEA prolongs
the AP by reducing the time-independent outward current rather than the
time-dependent outward current; and a TEA-sensitive current does not
effectively contribute to the total ionic current at the time of
Vmax(9).
10. The Effects of hypertension on cardiovascular responses to epinephrine
Cardiac beta-receptor responsiveness is diminished by both aging and
hypertension. In the study to evaluate of14 young and 18 older
normotensive men and women and in 10 young and 17 older hypertensive men
and women by echocardiography cardiac responses to intravenous infusion
of epinephrine and to assess the relative contribution of intrinsic
cardiac and counterregulatory components to the overall respons, found
that Epinephrine-induced increases in heart rate were similar in the four groups. Increases in stroke volume,
ejection fraction, and cardiac index were similar in the two
hypertensive and two young normotensive groups. In contrast, they were
attenuated in the older normotensive group, resulting in higher left
ventricular responses in older hypertensive than in normotensive
subjects. Heart rate and left ventricular
responses to epinephrine in the presence of ganglionic blockade did not
differ between the two young groups. Increases in plasma norepinephrine
due to epinephrine infusion were larger in hypertensive than in
normotensive subjects(10).
11. Epinephrine, vasodilation and hemoconcentration in syncopal, healthy men and women
In the study to evaluate why healthy young people may become syncopal
during standing, head up tilt (HUT) or lower body negative pressure
(LBNP by measuring the hormonal indices of autonomic activity along with
arterial pressure (AP), heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR) and measures of plasma volume,
found that the presyncopal decline in blood pressure in otherwise
healthy young people resulted from declining peripheral resistance
associated with plateauing norepinephrine and plasma renin activity,
rising epinephrine and rising blood viscosity. The increased
hemoconcentration probably reflects increased rate of venous pooling rather than rate
of plasma filtration and, together with cardiovascular effects of
imbalances in norepinephrine, epinephrine and plasma renin activity may
provide afferent information leading to syncope(11).
12. Adrenal glands and the activation of glucogenesis during undernutrition
In adults, the adrenal glands are essential for the metabolic response
to stress, but little is known about their role in fetal metabolism. In
the study to investigate the effects of adrenalectomizing fetal sheep on
glucose and oxygen metabolism in utero in fed conditions and after
maternal fasting for 48 h near term, showed that the circulating
concentrations of cortisol and total catecholamines, and the hepatic glycogen
content and activities of key gluconeogenic enzymes, were also less in
AX than intact fetuses in fasted animals. Insulin concentrations were
also lower in AX than intact fetuses in both nutritional states.
Maternal glucose utilization and its distribution between the fetal,
uteroplacental, and nonuterine maternal tissues were unaffected by fetal
AX in both nutritional states. Ovine fetal adrenal glands, therefore,
have little effect on basal rates of fetal glucose and oxygen metabolism
but are essential for activating fetal glucogenesis in response to
maternal fasting. They may also be involved in regulating insulin
sensitivity in utero(12).
13. Catecholamine concentrations in hyperthyroidism and hypothyroidism
In the study to measure the plasma epinephrine
(E) and norepinephrine (NE) concentrations in patients with thyroid
dysfunction, showed that hyperthyroidism is accompanied by normal plasma
NE concentrations and that hypothyroidism is associated with
significantly increased plasma NE concentrations, possible in an attempt
to compensate for the lack of thyroid hormones(13).
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Sources
(9) http://www.ncbi.nlm.nih.gov/pubmed/3785438
(10) http://www.ncbi.nlm.nih.gov/pubmed/17307999
(11) http://www.ncbi.nlm.nih.gov/pubmed/11695710
(12) http://www.ncbi.nlm.nih.gov/pubmed/20959526
(13) http://www.ncbi.nlm.nih.gov/pubmed/958003
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