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Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: The purpose of the study was to compare the renal effects of low doses of exogenous dopamine to assess the responsiveness of renal dopaminergic receptors in normotensive and hypertensive subjects. Eight hypertensive patients and seven normotensive volunteer subjects were studied. Inulin and para-aminohippuric (PAH) clearances, natriuresis, and fractional excretion of sodium increased significantly after intravenous dosing with dopamine (2 micrograms/min/kg) in both groups. These increases were significantly higher in hypertensive than in normotensive subjects: 31.8% +/- 3.7% vs. 16.2% +/- 1.2% for inulin clearance (P less than 0.01), 83.3% +/- 10.5% vs. 41.1% +/- 3.4% for PAH clearance (P less than 0.01), and 331% +/- 38% vs. 216% +/- 26% for natriuresis (P less than 0.01). These findings suggest hyperresponsiveness to dopamine during hypertension. This enhanced response to exogenous dopamine can be considered as a further argument favoring the existence of a deficit in dopaminergic activity during hypertension. Dopamine also induced a significant reduction in blood pressure and increased heart rate in hypertensive subjects but no significant change in blood pressure and heart rate occurred in normotensive subjects.
Output:
p-Aminohippuric Acid