Endogenous opioid system and atrial natriuretic factor in normotensive offspring of hypertensive parents at rest and during exercise test.
OBJECTIVE
To investigate the effects of the endogenous opioid system on plasma atrial natriuretic factor (ANF) levels during sympathetic hyperactivity.


METHODS
We studied the young normotensive offspring of parents who both had essential hypertension, who are characterized by a hyperactive sympathetic nervous system.


METHODS
We assessed plasma beta-endorphin, met-enkephalin, dynorphin B, ANF and noradrenaline levels, blood pressure and heart rate values in eight normotensive offspring and in 10 young normotensive subjects with no family history of hypertension (controls) at rest and during two exercise tests: the first test performed with the infusion of placebo (1.5 ml/min saline) and the second test with the infusion of an opioid antagonist (9.5 micrograms/kg per min naloxone hydrochloride). ANF and opioids were radioimmunoassayed after chromatographic pre-extraction.


RESULTS
At rest plasma met-enkephalin, dynorphin B, ANF and noradrenaline values in the normotensive offspring were significantly higher than in the controls. Exercise with placebo significantly raised all hormonal and haemodynamic parameters in the two groups. This increase was significantly higher in the normotensive offspring than in the controls. Naloxone did not modify any parameter in either group at rest, but it enhanced further the rise in plasma noradrenaline levels induced by exercise in both groups. A similar effect of naloxone during exercise was observed for plasma ANF levels in the normotensive offspring.


CONCLUSIONS
Our findings show that plasma met-enkephalin, dynorphin B, ANF and noradrenaline levels at rest and during exercise are higher in normotensive offspring than in controls. The effects of naloxone indicate that in normotensive offspring at rest the opioid system does not affect ANF release, whereas during exercise it attenuates ANF hypersecretion, possibly by reducing noradrenaline release.
Fontana
F
F
Istituto di Patologia Speciale Medica e Metodologia Clinica, Bologna, Italy.
Bernardi
P
P
Merlo Pich
E
E
Boschi
S
S
De Iasio
R
R
Capelli
M
M
Carboni
L
L
Spampinato
S
S
D000328:Adult; D009320:Atrial Natriuretic Factor / Q000097:blood*; D004198:Disease Susceptibility; D004399:Dynorphins / Q000097:blood; D004723:Endorphins / Q000097:blood; D004744:Enkephalin, Methionine / Q000097:blood; D005080:Exercise Test; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000235:genetics; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009638:Norepinephrine / Q000097:blood; D018847:Opioid Peptides / Q000097:blood*; D005082:Physical Exertion; D011863:Radioimmunoassay; D001615:beta-Endorphin / Q000097:blood
D004723:Endorphins; D018847:Opioid Peptides; D009270:Naloxone; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; C036200:rimorphin; D009320:Atrial Natriuretic Factor; D009638:Norepinephrine