Alpha 1-adrenergic receptor blockade reduces afferent and efferent glomerular arteriolar resistances in SHR.
To assess the effects of alpha 1-adrenergic receptor blockade on intrarenal hemodynamics of spontaneously hypertensive rats (SHR), terazosin (0.015 or 0.03 mg/kg body wt) or saline was injected into SHR or normotensive Wistar-Kyoto rats (WKY) (age 16-18 wk). Single-nephron glomerular filtration rate (SNGFR) and renal glomerular filtration rate were determined with [3H]inulin infusion; effective renal blood flow was measured with p-aminohippurate. Intrarenal efferent arteriolar, proximal tubular, stop-flow pressures measurements, and tubular fluid and efferent arteriolar samplings were obtained by micropuncture techniques. Terazosin reduced arterial pressure significantly in both rat strains, but only in SHR did alpha 1-inhibition decrease glomerular hydrostatic pressure (from 58.0 +/- 1.5 to 46.6 +/- 1.1 mmHg; P less than 0.05). Terazosin did not change SNGFR or single-nephron blood flow in either strain. As a result, only in SHR did efferent glomerular arteriolar resistances decrease (0.262 +/- 0.021 to 0.193 +/- 0.014 mmHg.ml-1.min; P less than 0.05). Glomerular ultrafiltration coefficient increased only in SHR (0.034 +/- 0.005 to 0.104 +/- 0.01; P less than 0.05). These results provide further support to the concept of alpha 1-adrenergic receptor hyperresponsiveness of efferent glomerular arteriolar in SHR but not WKY.
Division of Research, Alton Ochsner Medical Foundation, New Orleans, Louisiana 70121.
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D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007678:Kidney Glomerulus / Q000098:blood supply*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D011224:Prazosin / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; C041226:Terazosin; D011224:Prazosin