title: Long-term hypotensive effect of beta-agonist in conscious dogs.
abstract: The purpose of this study was to investigate the arterial pressure response to long-term administration of beta-agonists in the chronically instrumented conscious animal model. Chronically instrumented dogs were given intravenous infusions of ritodrine (2 micrograms.kg-1.min-1) for a period of 2 wk. Several cardiovascular and renal parameters were monitored before, during, and after the ritodrine infusion, and renal function curves were constructed. After the 1st wk of infusion, a new steady state was reestablished, and this was characterized by hypotension, reduced plasma protein concentration, elevated cardiac output, expanded extracellular fluid space, and near normal levels of activity of renin-angiotensin-aldosterone systems. The renal function curve during ritodrine infusion shifted to the left with no change in slope. We propose the following: 1) the persistence of hypotension is most probably related to the resetting of the arterial pressure-kidney blood volume servocontrol mechanisms, and 2) the persistent elevation of cardiac output and reduction in peripheral resistance are most probably related to increased oxygen and nutrient demand during beta-agonist infusions.
mesh_terms: D000450:Aldosterone / Q000097:blood; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001810:Blood Volume / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004285:Dogs; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007022:Hypotension / Q000139:chemically induced; D008297:Male; D010953:Plasma Volume / Q000187:drug effects; D011188:Potassium / Q000652:urine; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000097:blood; D012312:Ritodrine / Q000494:pharmacology*; D012964:Sodium / Q000652:urine; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D000450:Aldosterone; D012964:Sodium; D012083:Renin; D012312:Ritodrine; D011188:Potassium