Spontaneously hypertensive rats demonstrate increased renal vascular alpha 1-adrenergic receptor responsiveness.
To determine alpha 1-adrenergic receptor responsiveness of the renal vasculature in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), phenylephrine (2.5 or 5.0 micrograms.kg-1.min-1 iv) or saline was infused. Effective renal blood flow (ERBF) and glomerular filtration rate were determined by p-aminohippuric acid and inulin clearances, respectively. Peritubular capillary, proximal tubular, and stop-flow pressures (SFP) were measured by micropuncture. Phenylephrine decreased ERBF (6.27 +/- 0.48 to 4.55 +/- 0.65 ml.min-1.g-1; P less than 0.05) and increased arterial pressure and SFP (31.5 +/- 0.9 to 34.2 +/- 1.0 mmHg) in SHR. It only increased arterial pressure and ERBF in WKY without changing SFP. Afferent arteriolar resistance (RA) and glomerular capillary pressure (PG) remained unchanged, whereas efferent resistance (RE) decreased in WKY; in contrast, RA, RE, and PG increased in SHR (RA 21.2 +/- 2.0 to 38.1 +/- 7.1 mmHg.ml-1.min.g, RE 6.9 +/- 0.6 to 13.9 +/- 3.8 mmHg.ml-1.min.g; and PG 49.6 +/- 0.9 to 53.7 +/- 1.1 mmHg; all P less than 0.05). These data demonstrated increased SHR afferent and efferent arteriolar responsiveness; WKY efferent arteriolar hyperresponsiveness was not observed. The findings support the concept of augmented intrarenal vascular alpha 1-adrenergic responsiveness in hypertension that may predispose to subsequent glomerular hypertension.
Uchino
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Division of Research, Alton Ochsner Medical Foundation, New Orleans, Louisiana 70121.
Frohlich
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ED
Nishikimi
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Isshiki
T
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Kardon
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MB
D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000294:innervation; D002712:Chlorides; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012079:Renal Circulation / Q000502:physiology*
D017609:Barium Compounds; D002712:Chlorides; D011942:Receptors, Adrenergic, alpha; C024986:barium chloride; D010656:Phenylephrine; D001464:Barium