Atrial natriuretic peptide in the Milan hypertensive rat and the Milan normotensive rat: plasma concentration and binding to renal glomeruli in young, adult and aged rats.
METHODS
Blood pressures were determined in Milan hypertensive (MHS) and Milan normotensive (MNS) rats at different ages. Mean blood pressure, plasma atrial natriuretic peptide (ANP) concentration and renal glomerular receptors numbers and affinities were determined in young (25-day-old), adult (60- to 80-day-old) and aged (300-day-old) rats.


RESULTS
Mean blood pressures, always higher in the MHS than in the MNS rats, increased with age in both strains. Plasma ANP concentrations were similar in the young and aged rats of both strains, but were higher in the adult MHS than in the adult MNS rats. There were no quantitative differences in the ANP receptors between young and old rats of the two strains, but an increase in the maximal binding capacity was observed, in both strains, when adult rats were compared with young rats. Moreover, saturation experiments with [125I]-rat ANP revealed a downregulation of the ANP receptors in the renal glomeruli isolated from the adult MHS rats. In isolated glomeruli the cyclic GMP stimulation by ANP was similar in adult rats of both strains.


CONCLUSIONS
Downregulation in glomeruli of MHS rats, probably involving the clearance receptors for ANP, is concluded to occur.
Aptel
H B
HB
Sheffield University, Department of Animal and Plant Sciences, UK.
Deacon
C F
CF
Henderson
I W
IW
D000375:Aging / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000378:metabolism*; D001665:Binding Sites; D001794:Blood Pressure; D006152:Cyclic GMP / Q000096:biosynthesis; D004195:Disease Models, Animal; D015536:Down-Regulation; D006973:Hypertension / Q000097:blood / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000378:metabolism*; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism
D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP