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Physiological variations in ovine cerebrovascular calcium sensitivity
S E Akopov1, L Zhang, W J Pearce
1Department of Physiology, Loma Linda University School of Medicine, California 92350, USA.
The American Journal of Physiology
|May 1, 1997
Summary
Cerebrovascular reactivity to biogenic amines is influenced by calcium (Ca2+) sensitivity in blood vessels. Fetal arteries show greater reactivity than adult arteries due to differences in Ca2+ sensitivity and G protein mechanisms.
Area of Science:
- Physiology
- Vascular Biology
- Biochemistry
Background:
- Cerebrovascular reactivity to biogenic amines differs with arterial size and age.
- Existing research suggests these variations may stem from changes in contractile protein Ca2+ sensitivity.
Purpose of the Study:
- To investigate if cerebrovascular reactivity patterns are linked to Ca2+ sensitivity variations in contractile proteins.
- To compare Ca2+ sensitivity and biogenic amine responses in fetal versus adult sheep arteries.
Main Methods:
- Permeabilized arterial segments (common carotid, basilar, middle cerebral) from adult and fetal sheep were used.
- Beta-escin was employed for permeabilization, with methods validated for each artery type.
- Myofilament Ca2+ sensitivity was assessed, and responses to serotonin and guanosine 5'-O-(3-thiotriphosphate) were measured.
Main Results:
- Baseline myofilament Ca2+ sensitivity increased from common carotid to middle cerebral arteries and was higher in fetuses than adults.
- Serotonin dose-dependently increased Ca2+ sensitivity via G protein pathways in all arteries.
- Serotonin's effect on Ca2+ sensitivity was significantly greater in fetal than adult arteries.
Conclusions:
- Cerebrovascular reactivity to biogenic amines is partly determined by baseline myofilament Ca2+ sensitivity.
- G protein-dependent alterations in Ca2+ sensitivity contribute to observed reactivity patterns.
- Fetal arteries exhibit distinct Ca2+ sensitivity and G protein-mediated responses compared to adult arteries.