Effects of alpha1-blockade on the forearm vascular resistance responses to lower body negative pressure in young borderline hypertensives.
To determine whether alpha1-blockade affects the forearm vascular resistance responses to lower body negative pressure (LBNP) in borderline hypertensives, six hypertensives (HTN; mean arterial pressure [MAP] = 109.9 +/- 1.7 mm Hg, mean +/- SE) and seven normotensives (NTN; MAP = 81.5 +/- 1.4 mm Hg) underwent exposures of LBNP at pressures of -10, -20, and -40 mm Hg during systemic alpha1-receptor blockade (BLK) and during placebo (PLA). Resting forearm vascular resistance (FVR) was greater in HTN than in NTN during PLA (34.8 +/- 5.4 v 17.5 +/- 3.1 units; P < .05), but not during BLK (28.1 +/- 5.2 v 25.3 +/- 9.9 units). When expressed as a percentage of resting FVR, LBNP evoked an increased FVR (P < .001) that did not differ significantly between BLK and PLA in either group. FVR was higher (P < .001) in HTN than in NTN throughout both trials; at -40 mm Hg of LBNP during BLK, the increase in FVR was greater (P < .05) in HTN than in NTN (131 +/- 42 v 48 +/- 15%). MAP (relative to resting) was maintained throughout LBNP during PLA but, at -40 mm Hg, was lower (P < .01) during BLK for both groups. HR was elevated in BLK and was increased at -40 mm Hg (P < .01) for each group in each trial. This increase was greater during BLK (P < .05). These data suggest that borderline hypertensives have a greater vasoconstrictor response to LBNP than do normotensives and alpha1-blockade does not appear to attenuate this response.
Franke
W D
WD
Department of Health and Human Performance, Iowa State University, Ames 50011, USA. wfranke@iastate.edu
LaVere
S N
SN
D058668:Adrenergic alpha-1 Receptor Antagonists; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D003080:Cold Temperature; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008150:Lower Body Negative Pressure; D011311:Pressoreceptors / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects*
D058668:Adrenergic alpha-1 Receptor Antagonists