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Table 3 Intravenous Cardiovascular Effects of PGA and
PGE in the Normatensive Dog
Components
PGA and PGE
Blood pressure Peripheral arterioles Total peripheral resistances Heart rate Myocardial contractility Regional blood flow given IA Sodium and potassium excretion Urine flow Plasma volume
Lowered Dilated Lowered Reflex increase Unchanged Increased Increased Increased Decreased
Blood Pressure-Lowering Effects in Normotensive Animals
A sustained intravenous infusion of PGA, or PGA, results in an initial fall in blood pressure (the result of peripheral arteriolar dilatation), leading to a fall in total peripheral resistance and a reflex bar receptor-mediated acceleration in heart rate. Evidence has accumulated that the splanchnic vascular bed largely mediates the hypotensive action of PGA. Thus intraarterial administration of PGA or PGE compounds to normatensive animals results in an increase in regional blood flow in the carotid, coronary, cutaneous, splanchnic, femoral, brachial, and renal systems. However, only intra-arterial administration into the splanchic bed results in a concomitant fall in blood pressure. This suggests that hypotension induced by PGA or PGE is largely the result of splanchnic arteriolar dilatation. Support for this hypothesis is provided by the observation that, upon intravenous administration of PGA to dogs, the fall in blood pressure is accompanied by a simultaneous rise in splanchnic blood flow and an unchanged or decreased flow to most other vascular beds. Within 10 to 15 minutes, blood pressure returns to the pre injection level despite continued PGA administration.
This is a reflection of adaptive pressor mechanisms being elicited to offset the unphysiologically low blood pressure fall induced by prostaglandin.
94
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TORET 4511 310 132-133
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