Renal Hemodynamic Response of Unanesthetized Dogs to Positive Acceleration

摘要

Trained unanesthetized dogs were exposed to positive centrifugal accelerations up to +6Gz. Renal arterial pressure and inferior vena cava pressure at kidney level were measured through indwelling catheters. Renal blood flow velocity was measured by a Doppler principle ultrasonic flow meter. The flow signal was telemetered and the pressure signals were transferred by slip rings from the centrifuge. About 10 days after the sensing devices were implanted, under pentobarbital anesthesia, the experiments began for which the dogs were unanesthetized. The mean pre-acceleration mean renal arterial pressure, arterial-venous pressure gradient, and flow velocity were respectively 140 plus or minus 2 (S.E.) mm Hg, 133 plus or minus 2 mm Hg and 27 plus or minus .4 cm/sec. Renal flow velocity decreased in proportion to plus Gz to a minimum of 4.5 plus or minus .8 cm/sec during +6Gz. Mean renal arterial pressure rose at all G levels to 160-170 mm Hg. The pressure gradient was stable up to +3Gz, and decreased at +4, 5, and 6Gz to 76 plus or minus 7 mm Hg during 06Gz. Intrarenal phenoxybenzamine, 150 micro gm/min x 30 min, which did not alter pre-acceleration renal arterial pressure and blood flow velocity, partially inhibited the flow velocity reduction during +Gz. Intrarenal vasoconstriction mediated by alpha adrenergic receptors is part of the response to +Gz. (Author)