Sažeci 2. Hrvatskog kongresa medicinske biokemije - Klinički zavod ...

Sažeci 2. Hrvatskog kongresa medicinske biokemije
SEKCIJSKA PREDAVANJA
CATECHOLAMINES, ENDORPHINS,
BIOACTIVE PEPTIDES AND STRESS
S4/3
O. Zinder
Rambam Medical Center Haifa, Israel
The human response to stress is a complex physiological event
involving numerous neuronal and metabolic pathways. The perception
of stress, vvhether physical or psychological, triggers the activation
of a cascade of events usually initiated at the level of the hypothalamus.
This series occurs via secretion of a number of peptide
molecules which act as releasing or inhibiting factors in the continuation
of the stress response cascade. These peptides include CRF
(Corticotropin Releasing Factor), PRF (Prolactin Releasing Factor),
TRF (Thyrotrophic Releasing Factor) and others. These compounds
flow through the neural pathways in the brain and activate secretion
of hormones (Prolactin, TSH, GH, others), trophic substances (ACTH)
and peptide precursors such as POMC (Pro-opio-melano-cortin), from
the pituitary gland. While POMC acts as a narent compound, stimulated
by CRF to be secreted and broken down to ACTH, P-lipoprotein
and MSH, the other secretory products of the pituitary have an immediate
and profound effect on peripheral tissues, e.g. stimulation of
cortisol secretion by the adrenal gland. Endorphines, the endogenous
opiates are released via POMC cleavage, and exert their effect mainly
within the central nervous system, binding to pain receptors and inhibiting
their response. Catecholamines are quickly released in the
brain, the sympathic nervous system, and from the adrenal medulla,
in response to stress. The regulatory activities of the catecholamines
in maintaining blood glucose levels, providing free fatty acids as metabolic
fuel, and adjusting cardiovascular pressures, are key factors in
maintenance of physiological homeostasis. The adrenal medulla also
contains very large amounts of enkephaline (as well as other active
peptides) which are co-stored together with epinephrine and not with
norepinephrine. Secretion from the adrenal medulla following stimulation
by acetylcholine shows preferential release of norepinephrine,
vvhile basal secretion is mainly epinephrine. The mechanism of secretion,
its physiological consequences, the clinical relevance and diagnostic
importance in measurement of these regulatory compounds, and
their action on peripheral tissues will be discussed.
54 BIOCHEMIA MEDICA god. 6, br. 1, 1996.