Catecholamine clearance is not enhanced by increasing levels within the physiological range.
If rising plasma catecholamine levels enhance their own clearance, such a mechanism could be protective, and its absence predispose to hypertension. In normal subjects and in mild essential hypertensives serial increases in plasma noradrenaline (NA) and adrenaline (ADR) generated by intravenous infusion were used to test the effect of rising plasma levels on clearance. Plasma NA and ADR were measured radio-enzymatically, venous clearance of NA by isotopic infusion and clearance of ADR by increment in arterial plasma levels. Serial increases in NA and ADR through the physiological range did not lead to increased plasma clearance: in fact, NA and NA clearance were significantly negatively correlated. For ADR, a circulating hormone, any effect on clearance may be biologically important. Chronic increases in circulating ADR due to mental stress have been suggested as an etiological factor in essential hypertension, working through enhanced noradrenergic transmission. The significance of these findings for NA, a local neurotransmitter rather than a circulating hormone, depends on the extent to which changes in plasma clearance reflect changes in tissue clearance.
Gordon
R D
RD
Endocrine-Hypertension Research Unit, Greenslopes Hospital, Brisbane, Australia.
Bachmann
A W
AW
Mikulecky
M
M
Gueizelar
B T
BT
D000293:Adolescent; D000328:Adult; D004837:Epinephrine / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood / Q000378:metabolism*
D009638:Norepinephrine; D004837:Epinephrine