| Summary: | This investigation was undertaken in an attempt to establish the possible physiological functions of Dopamine (DA) in the rat. From the results obtained in normal and adrenalectomized rats, it is possible to say that: (a) The main source of urinary DA is not the adrenal gland but possibly the kidney. This conclusion is based on the results obtained after measuring urinary DA excretion in normal and adrenalectomized rats before and after treatment with sodium chloride and frusemide. (b) Chloride loading is possibly an important and an independent factor influencing DA excretion in the rat. This view is derived from the fact that a significant correlation exists between administered and excreted chloride and urinary DA excretion in the rat. (c) DA induces a dose-dependent diuresis, natriuresis but decreased potassium excretion in normal rats. (d) While DA-induced diuresis and decrease in potassium excretion were observed in normal and adrenalectomized rats, the natriuresis seen in normal was absent in the adrenalectomized rats. (e) Although the DA-receptor antagonists, cis-flupenthixol and sulpiride had no effect on DA-induced diuresis in normal and adrenalectomized rats, they inhibited DA-induced natriuresis and tended to be additive to the effect of DA on potassium excretion in normal rats. This decrease in sodium excretion may indicate a role for endogenous DA in modulating sodium excretion. (f) In the experiments in which DA was administered to normal and adrenalectomized rats before and after treatment with (i) aldosterone and the DA-receptor antagonists; (ii) normal rats after spironolactone and aminoglutethimide treatments, it is not possible to draw any definite conclusion as to the possible relationship between DA and the renin-angiotensin- aldosterone system. However, what seems clear from these results is that there seems to be separate mechanism(s) for DA-induced diuresis, natriuresis and its effect on potassium excretion which may well reflect on the separate "pumps" within the kidney controlling these parameters.
|
|---|
