Atrial natriuretic peptides in canine hypoxic pulmonary vasoconstriction.
OBJECTIVE
The aim of the study was to investigate whether atrial natriuretic peptides have a physiological role in regulation of the pulmonary circulation.


METHODS
Plasma concentrations of immunoreactive atrial natriuretic peptide and guanosine-3',5'-cyclic monophosphate (cGMP) were measured during evaluation of pulmonary vascular tone by multipoint pulmonary arterial pressure-cardiac index (Ppa/Q) relationships.


METHODS
Experimental animals were 17 mongrel dogs of either sex, 21-35 kg weight, anaesthetised with pentobarbitone.


RESULTS
Measurements of Ppa/Q relationships and atrial natriuretic peptide/cGMP were made during hyperoxia (Fio2 0.4) and hypoxia (Fio2 0.1). Hypoxic pulmonary vasoconstriction, defined as hypoxia induced increase in pulmonary artery pressure over the entire range of Q studied from 2-5 litre.min-1.m-2, was elicited in nine dogs ("responders"). In the other eight dogs, hypoxia did not change pulmonary artery pressure over the entire range of Q studied ("non-responders"). At neither the highest nor the lowest Q in hyperoxia did atrial natriuretic peptide and cGMP concentrations differ between these two groups, nor did acute reduction in Q affect the concentrations in either group. At the highest Q, plasma atrial natriuretic peptide increased in hypoxia from 11(SEM 2) to 15(3) pmol.litre-1 in the responders (p less than 0.05), and from 15(2) to 20(2) pmol.litre-1 in the non-responders (p less than 0.05). However at the lowest Q, atrial natriuretic peptide was increased in non-responders only, from 17(3) to 23(4) pmol.litre-1 (p less than 0.05). CGMP did not vary significantly in any experimental condition.


CONCLUSIONS
Hypoxia slightly increased plasma atrial natriuretic peptides without any relationship with associated pulmonary haemodynamic changes. These data do not support the hypothesis that atrial natriuretic peptides play a physiological role in the regulation of the pulmonary circulation in dogs.
Vachiery
J L
JL
Laboratory of Physiology and Pathophysiology, Faculty of Medicine, Free University of Brussels, Belgium.
Lejeune
P
P
Hallemans
R
R
Brimioulle
S
S
Debiève
M F
MF
Abramow
M
M
Naeije
R
R
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000502:physiology*; D001794:Blood Pressure; D002302:Cardiac Output; D006152:Cyclic GMP / Q000097:blood; D004285:Dogs; D005260:Female; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D008297:Male; D011652:Pulmonary Circulation / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*
D009320:Atrial Natriuretic Factor; D006152:Cyclic GMP