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KMID : 0438219760130010081
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Korea University Medical Journal
1976 Volume.13 No. 1 p.81 ~ p.87
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Effect of Alpha-adrenergic Blocking Agent on the Pitressin Inhibiting Action on Noradrenalin
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Abstract
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The infusion of noradrenalin, the principal endogenous alpha-adrenergic agent, to man and animal have been shown to increase urine volume and free water clearance without altering glomerular filtration rate but occasionally apparent reduction of renal plasma flow.
This effect was the most marked in subjects who started with a negative free water clearance, presumably resulting with elevated levels of antidiuretic hormone.
The several reports-have been showed that noradrenalin antagonizes action of antidiuretic hormone on the toad bladder in vitro, and the action of exogenous antidiuretic hormone given to water loading subjects also inhibits by noradrenalin in vivo.
Many of the polypeptide hormones, including antidiuretic hormone, cause activation of adenyl cyclase as a step in their mechanism of action. This enzyme has been thought of as the beta-adrenergic receptor.
Alpha-adrenergic drugs cause diuresis but beta-adrenergic drugs antidiuresis in the normally hydrated rat.
To clarify the mechanism by which adrenergic drug alter water excretion and the action of antidiuretic hormone, water were infused with combinations of these drugs and its blocking agent into unanesthetized rabbit.
On experiments 20 rabbits were infused with 2.5% dextrose solution until water diuresis was
maintained and thereafter simultaneous administration of pitressin (20 micro U/kg per min), pitt ressin (20 micro U/kg per min) plus noradrenalin(0.5 micro g/kg per min) and then pitressin(20
micro U/kg per min) plus noradrenalin (0.5 micro g/kg per min) plus regitin (3.5 micro g/kg per
min) were successfully performed. During experiments urine volume, inulin clearance, osmolar
clearance, free water clearance and sodium excretion were measured for four consecutive ´specimens every twenty minutes intervals respectively.
The results were as follows:
(1) Water diuresis was inhibited by pitressin.
(2) Pitressin induced antidiuresis was inhibited by noradrenalin:
(3) Regitin, alpha-adrenergic blocking agent inhibited the effect bf noradrenalin on pitressin induced antidiuresis.
(4) Osmolar clearance, free water clearance; kiomerular filtration rate and sodium excretion Were not altered by pitressin, noradrenalin and regitin,
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